INTRODUCTION

As an element, mens rea serves the critical purpose in criminal law of differentiating behavior by degrees of culpability. Through mens rea, acts and harms are placed on a continuum of fault that gives accidental conduct the lowest level of fault and deliberate or premeditated conduct the highest and most blameworthy level of fault. Mens rea not only draws boundaries between criminal and noncriminal events, but it cabins those events and assigns punishment based on the degree of the actor’s culpability.

Inevitably, the inquiry into the state of mind element often requires a fact finder to contemplate what a defendant was thinking. Absent a defendant’s disclosure of his own thoughts, fact finders are often left to infer a mental state from the defendant’s actions. Even if a defendant offers insights into his mental state, the fact finder must still weigh the credibility of the defendant’s confession against the fact finder’s own perception of the world. Whether by the defendant’s confession or the fact finder’s inference, the calibration of mental state is filtered through the fact finder’s own thought process and life experience. This filtering is not without judicial and legal guidance. In most jurisdictions and in the Model Penal Code (“MPC”), the law defines mental states and judges offer jury instructions designed to provide guidance as to the meaning of the mens rea element. Each of these definitions, however, proceeds from the premise that mental states are uniform and adult referential. Under this approach, all thought and thought processes are adult, and the proper analytic baseline for mens rea is an adult’s understanding of the world.

This Article argues that this one-size-fits-all approach to mens rea is not only inconsistent with scientific evidence that the cognitive processes of adolescents differ from those of adults, but also undermines the purpose of mens rea when applied to juvenile offenders. As a result, I argue that the mens rea standard as applied to juveniles should be recalibrated to account for what is now known about adolescent development.

Such an argument is consistent with the Supreme Court’s recent decisions in Roper v. Simmons,¹ Graham v. Florida,² Miller v. Alabama,³ and J.D.B. v. North Carolina,⁴ as well as its longestablished jurisprudence of youth. In the Roper trilogy and J.D.B., the Supreme Court noted what many have long suspected: children and adolescents do not engage in the same decision-making processes as adults. As a result, the Roper line reasons, adolescents may not achieve the same level of culpability as their adult counterparts, and therefore are ineligible to receive the death penalty or, in some circumstances, a sentence of life in prison without the possibility of parole. In this, the Court recognized the role of the mental state element in assessing culpability.⁵ The Court’s refusal to subject juveniles to particular punishments was premised on the acknowledgement that immature thought processes rendered adolescents less culpable, at least as compared to their adult counterparts.

This assessment of culpability in the context of punishment certainly has some idiosyncrasies. Most notably, substantive criminal law purports not to share punishment theory’s abiding interest in the potential for rehabilitation or even the probability of reoffense in its assignment of guilt.⁶ Despite this difference, the culpability analysis for punishment and the culpability analysis for substantive criminal law both purport to judge the defendant’s level of guilt based on what is known of the defendant’s actions and the harm he caused. In this calculation, whether in judgment of guilt or punishment, the defendant’s state of mind matters as it signals a variance in the defendant’s level of culpability.

The Roper line acknowledged this premise for punishment, and J.D.B. expanded this premise’s application in the context of Miranda.⁷ In J.D.B., the Court concluded that it is erroneous to use the same standard of reasonableness when assessing the juvenile defendant’s perception of custody for Miranda purposes.⁸ While these decisions have been lauded as striking new ground in the context of Eighth Amendment jurisprudence by categorically prohibiting previously permissible sentences for juvenile offenders—and Fourth Amendment jurisprudence by creating an “age appropriate” standard of reasonableness—they all toed a well-worn path that the Court and the law more generally had constructed with regard to youth. This jurisprudence of youth was premised on the acknowledgment that children were different than adults, and therefore enjoyed a distinct legal status. Even in the context of sentencing, over a decade earlier, the Court remarked that the law must recognize that adolescents tend to be more impetuous, reckless, and immature than adults.⁹

The Roper line and J.D.B. will undoubtedly be recognized as watershed moments in the context of Eighth and Fourth Amendment jurisprudence, but their greatest significance may lie elsewhere. In these cases, the Court relied for the first time on scientific studies to support the doctrine of difference that it had previously staked out with regard to youth. Using these studies, the Court concluded with heightened conviction that children think differently than adults, and that this difference, at least in the context of punishment and perceptions of custody, signals a need for the application of a different legal standard to adolescents.

As significant as this pronouncement is, it has remained confined to punishment and Miranda’s custody analysis. While the Court significantly expanded its consideration of adolescent thought processes in J.D.B. to encompass the perception of custodial status, thus far courts have declined to extend Roper’s and J.D.B.’s analysis to culpability standards contained in the substantive criminal law concept of mens rea. This seems odd as the conceptual premise of these two lines holds equally true in the context of substantive criminal law. It therefore seems only logical that—just as the Court has developed a Fourth and Eighth Amendment jurisprudence that recognizes the differences between adult and adolescent thought processes—so must a parallel jurisprudence evolve around mens rea and the most basic question it seeks to answer: is the adolescent guilty in the first place? This Article makes the novel argument that applying current, adult-based mens rea standards to adolescent defendants is not only logically inconsistent with the Court’s position in Roper and J.D.B. and its more global jurisprudence of youth but that such an application fundamentally undermines the very function of the mental state element.

The principal goal of this Article is to lay the foundation for the application of adolescent neuroscience in the sphere of substantive criminal law. This is an important first step, but it is only a first step and larger questions inevitably linger. What proof problems would a juvenile-centric mens rea approach create? How would substantive defenses be affected? Is such an approach likely to change outcomes? What does such an approach suggest about the juvenile criminal system itself? These and other questions are difficult ones, and I look forward to engaging these lingering questions in future work. While this Article does not address all of these important issues, it opens an avenue of discussion that previous scholarship in the area has yet to address: that what is known about adolescent brain development must inform our calculation of juvenile mens rea.

In order to achieve the purported function of mens rea, courts must recognize that an analysis of a state of mind element must encompass consideration of the distinct processes and capabilities of adolescents. In short, the fact finder must view the factual narrative of the case from the defendant’s perspective. Courts cannot accept on faith that an adult fact finder will faithfully remember or properly assign meaning to the actions of adolescent defendants. Instead, courts must both allow the presentation of evidence on the distinct thought processes that are the hallmark of normal¹⁰ adolescent development and offer instruction to fact finders to consider these distinctions in their calculation of the defendant’s state of mind.

While proponents of juvenile neuroscience in the context of the Eighth Amendment in particular have cautioned against its premature use in substantive criminal law realms, such caution undervalues the relevance of the scientific evidence to mens rea and undermines the value of the mental state element itself. Such caution is premised on the notion that substantive criminal law’s continued reliance on adult standards of mens rea remains an appropriate calibration of adolescent guilt. Whatever limitations the current state of science suffers, it provides sufficient insight to confirm that continued use of an adult-centric mens rea standard for juvenile offenders provides inaccurate insights into the adolescent’s actual guilt under the law.

I make this argument in four parts. I begin with an examination of substantive criminal law’s efforts to define culpability in terms of an actor’s state of mind. In this discussion, mens rea emerges as a critical element whose articulated purpose is to distinguish and categorize levels of blameworthiness. In Part II, I turn to the Supreme Court’s construction of the jurisprudence of youth. Just as the law classifies youth and assigns legal significance to this classification, so too has the Court constructed a doctrine around youth generally and adolescence specifically. In the fortification and expansion of this doctrine, the Court has increasingly relied on the science of human development to set the boundaries of juvenile culpability. In Part III, I consider the emerging scientific evidence surrounding juvenile brain development and its implications for executive function, in particular the willingness of adolescents to engage in risky behavior and their failure to understand the long-term consequences of decisions. Finally, in Part IV, I conclude that. given the critical role that substantive criminal law assigns mens rea as the arbitrator of culpability, the development of a jurisprudence surrounding youth, and the emerging body of scientific literature supporting the distinction between adult and adolescent decision-making processes and capabilities, the current application of an adult-based mens rea standard is not only based on a false premise, but undermines the purpose of the state of mind element itself.

I. MENS REA’S ROLE IN CRIMINAL LAW

At its core, criminal law links notions of culpability and blameworthiness.¹¹ Though intertwined, these are distinct concepts. At the most basic level, the actor’s moral blameworthiness is a necessary prerequisite for state-imposed punishment, though alone it is insufficient.¹² If blameworthiness designates an act as morally wrong, culpability places that “wrongfulness” on a continuum of fault, defining and categorizing the actor’s transgression. In this, the concept of mens rea is critical. Mens rea, or the requirement of a mental state, seeks to differentiate between acts that are blameworthy and those that are culpable and therefore deserve punishment.¹³ In this determination, the act or even the harm it may have caused is not enough. The presence or absence of a mental state is the difference between an accidental or unintentional act and one that deserves punishment.¹⁴ As Justice Holmes famously noted, criminal law pivots around this distinction: “[E]ven a dog distinguishes between being stumbled over and being kicked.”¹⁵ Holmes’s dog sensed what the drafters of MPC, and countless legislative bodies, have attempted to enshrine in statute: an act without a mental state is usually not a crime.¹⁶ The act may still cause harm and may even cross over into the wasteland of moral blameworthiness, but the absence of a mental state generally renders it nonculpable and thus unworthy of stateimposed punishment.¹⁷

While mens rea may be an imprecise caliper, it nonetheless establishes the threshold between concepts of moral blameworthiness and culpability.¹⁸ Mens rea seeks to sort acts into categories of culpability with the dual purposes of establishing sufficient culpability to justify a particular punishment¹⁹ while protecting against the imposition of disproportionate punishment.²⁰ While the Supreme Court has declined to designate mens rea as a constitutionally mandated element under the Due Process Clause, it does recognize that the concept is integral to notions of culpability, justice, and punishment.²¹ While strict liability crimes or crimes with no mens rea requirement certainly exist, they are both in the minority and generally disfavored.²² The MPC, in fact, requires readers to impose a mental state requirement in otherwise silent statutes unless the legislature clearly designates it as a strict liability offense.²³

Thus, while proof of all elements beyond a reasonable doubt is necessary for conviction and punishment, mens rea serves a unique role, seeking to separate acts that cause harm from those that both cause harm and implicate the actor as culpable. Mens rea is the difference between Holmes’ stumble and kick. In this difference, a line is crossed and the harm becomes the subject of state attention and condemnation.

But to unpack this concept is to enter into an amorphous realm in which ordinary fact finders are asked to engage in the hard task of discerning what any particular actor was actually thinking. It is to realize that the very concept of mens rea grows from a bedrock of assumptions. First, mens rea assumes a baseline understanding of social norms.²⁴ These social norms designate certain actions as “wrong” and, therefore, prohibited under the law.²⁵ This assumption is linked to the concept of “notice” in criminal law. Citizens are not required to know every law, but they are assumed to know and understand rules that dictate social interactions.²⁶ A citizen does not have to know which statute criminalizes homicide and which nuances distinguish murder from manslaughter, but it is assumed that all citizens know that they are not permitted to kill one another—at least not with legal impunity.²⁷

Not unrelated, the doctrine of mens rea further assumes that a citizen is capable of conceptualizing his actions in the context of these social norms and expectations. In terms of the distinction between blameworthiness and culpability, a citizen may well be blameworthy for a cognitive and volitional act that causes a harm, but the law may hesitate to attach culpability absent some evidence that the actor had some understanding that his actions were (or at least should be) prohibited by social norms.²⁸

This second assumption in turn leads to a third—that a citizen is a member of social networks that enforce and enhance her understandings of social norms.²⁹ One challenge that arises when the law is reduced to a static writing is that social norms may shift or outpace the law’s prohibitions.³⁰ As a result, some laws may fail to reflect social norms in some or all communities, either over time or even at their inception.³¹ The law itself, in seeking to account for this disconnect, may undergo a series of interpretations either in its formal enforcement by government actors or in its informal enforcement by citizens themselves serving as voters and fact finders.³² By maintaining a connection with social networks, a citizen may come to understand not only what the law formally prohibits but also the degree of that prohibition, the culpability that attaches to violating the prohibition, and perhaps the community-specific exceptions to the prohibition. In this, the concept of mens rea would seem to assume that a citizen not only has a singular understanding of social norms and how her actions fit into the expectations of those norms, but also that a citizen has a fluid and evolving concept of such norms that allows her to weigh her own actions in any given situation against society’s malleable notions of right and wrong.

Despite a citizen’s membership in social networks that facilitate contextualization of actions, as a doctrine mens rea assumes both that a citizen is capable of understanding the consequences of his actions and that he does so in reasonable alignment with his community’s understanding of such consequences.³³ In short, an actor must understand before he acts both that his action will cause a particular effect and that there are prohibitions surrounding them. Even if an actor does not fully understand the potential illegality of his act, he must understand the harm it may cause and the nature of the act as unacceptable or criminal in his community. This ability to grasp the cause-and-effect relationship for any given act is fundamental to theories of punishment. This in turn requires that defendants are rational, capable of understanding social norms and choosing to abide by them or not, and capable of self-reflection.³⁴

Implicit in this assumption is the notion that any given citizen is capable of making independent choices to abide by or to disregard social norms and law³⁵ and that these choices will be driven by an analytic process that takes into account communal values and restrictions and the actor’s own needs or desires.³⁶ In short, the concept of mens rea renders an act of disobedience an active one, a decision not to comply in a world where the norm is compliance.³⁷ Mens rea transforms the decision to break the law into an act of citizen defiance differentiated by the level of culpability the actor’s thought processes reflect.

A. Brief History of Mental States

Despite its critical role in establishing culpability, efforts to define the state of mind requirement have, historically, been somewhat elusive. Early civilizations defined culpability broadly as the distinction between accidental and nonaccidental acts.³⁸ Even as criminal codes advanced and elements dwindled or acts were decriminalized, the mens rea requirement remained central to notions of culpability.³⁹ Within the broad rubric of the mental state, legal distinctions surfaced between degrees of culpability. Acts, and the crimes they implicated, were defined on a spectrum that spanned from carelessness to intentionality to premeditation. Along this spectrum, culpability was judged based on the degree of blameworthiness calibrated by the actor’s state of mind.⁴⁰

Most crimes required a mental state beyond mere negligence or carelessness. As governments and societies sought to define states of mind that exceeded negligence, categories proliferated and labels abounded.⁴¹ First, the law began to differentiate between a careless act and one that demonstrated a higher degree of culpability, but still hovered somewhere below a desire to cause harm.⁴² Regardless of the descriptive label, such actors were distinct from negligent actors— they harbored knowledge of the harm risked by their acts and elected to act anyway.⁴³ These “negligent plus” actors had some comprehension of the risk their behavior posed and yet took the risk anyway in the hopes of achieving some alternative, presumably desired, result. This distinction between mental states recognized that the actor who comprehended the risk and yet acted anyway was qualitatively distinct from her inattentive or negligent counterpart and therefore more deserving of punishment.⁴⁴

Within the canon of American criminal law, an additional distinction has developed on the continuum of accidental and nonaccidental acts with the differentiation of “intentional acts.”⁴⁵ This distinction created a category of mental state acknowledging that an actor may consciously undertake an act knowing that a particular harm, though not desired, is virtually certain to occur if the actor acts.⁴⁶ This mental state hovers somewhere above recklessness but below intentionality, occupying a space of “recklessness-plus.”

Finally, in the context of homicide, common law recognized an additional level of mens rea—“premeditation,” which signals a heightened level of intentionality.⁴⁷ In nearly every state, a finding of deliberation or premeditation is a necessary prerequisite for the most serious punishment—mere intentional killings simply do not warrant the most severe category of punishment.⁴⁸

In addition to designing these degrees of culpability around particular mental states, the common law also generated defenses contingent on the establishment of a mental state or its absence.⁴⁹ Excuse and mitigation defenses offer varying degrees of shelter from liability, either because the offender is very different from ordinary actors or the offender is ordinary but acted in response to extraordinary or aberrant circumstances.⁵⁰ These defenses consider how the actor’s mental condition or circumstances affect his thought process and consequently shape his mental state.⁵¹ Some defenses expressly contemplate the offender’s state of mind or mental capacity in their construction.

Of these defenses, an insanity defense is the most extreme, excusing liability based on both the mental condition of the actor and the effect of that condition on her understanding of the wrongfulness of her act.⁵² The defense of diminished capacity is similar to an insanity defense in that both expressly consider an actor’s mental condition, including possible defects in the calculation of culpability. A diminished capacity defense, however, mitigates rather than excuses liability but still takes into account the offender’s state of mind.⁵³ Likewise, the doctrines of extreme emotional disturbance, provocation, and heat of passion all recognize that particular circumstances may affect an actor’s mental state and thereby mitigate culpability.⁵⁴ Unlike insanity, these defenses do not completely insulate the defendant from liability, but rather suggest that she acted under a different or diminished mental state that warrants consideration in an assessment of guilt and punishment.⁵⁵

These mitigation defenses are the most obvious mens rea–based defenses, but they are not the only ones. The doctrine of self-defense likewise relies on an assessment of the defendant’s mens rea, though it does so in a less obvious way.⁵⁶ While the particulars of the selfdefense doctrine have varied widely throughout its evolution, at its core the doctrine depends on the fact finder’s determination that the defendant’s use of force was a reasonable response to the threat he believed he faced.⁵⁷ Implicit in this assessment of the defendant’s reasonableness is an evaluation of what the defendant believed the situation to be at the moment he calculated his response.⁵⁸ In short, the fact finder must determine the defendant’s state of mind as it relates to the perceived threat.⁵⁹ Thus, while at first blush this defense would appear distinct from either the concept of mens rea itself or an excuse defense that relies on the absence of mens rea to mitigate culpability, in reality, the concept of self-defense is entwined with the same doctrinal principles used to define the defendant’s state of mind.⁶⁰ In this sense, whatever other criticisms one might levy against this or any other defense, an examination of such defenses is an instrumental part of the analysis of mens rea’s role as a tell of culpability.

This common-law evolution of mental states and the defenses they implicate was hardly linear or precise. As social norms and expectations shifted, so too did concepts of mens rea.⁶¹ Like many legal standards untethered to particular statutes or rules,⁶² the state of mind element became a mechanism for fact finders to approximate the justice of verdicts and punishments.⁶³ This may in fact be one of the great virtues of unattached standards: they demand interpretation in ways that rules—which cede this power to their drafters—do not.⁶⁴ In the process, however, definitions inevitably overlapped, conflicted, or even disappeared altogether.⁶⁵ Internal debates emerged over whether mens rea standards should be judged objectively or subjectively and, as will be discussed in greater detail below, whether such distinctions were even possible.⁶⁶

Sadly, the development of the criminal code in the United States did little to resolve these debates or identify with precision the meaning of the mens rea requirement.⁶⁷ The Supreme Court, in surveying the criminal code, lamented that the mens rea element produced “disparity and confusion” because it lacked a precise definition.⁶⁸ Despite this reality, there was no effort to establish general culpability definitions within criminal statutes⁶⁹—at least not until the American Law Institute (“ALI”) and Herbert Wechsler decided to offer uniform mens rea definitions in the MPC.⁷⁰

B. The Rise of the MPC and Defined Mens Rea

The MPC divides mens rea into four categories: purposely,⁷¹ knowingly,⁷² recklessly,⁷³ and negligently.⁷⁴ These categories were created in an attempt to resolve the conflicts that arose as a result of the common law’s failure to define mental states. First, while the ALI retained previous distinctions between purposeful and negligent acts, it limited the further division of culpability to two additional categories: knowingly and recklessly.⁷⁵ Within these categories of mens rea, culpability was defined either in terms of the actor’s desires or the risk she took, or both.⁷⁶ Second, the ALI embedded mens rea requirements into the definitions of crimes themselves, requiring that all crimes have, at minimum, both act and mental state requirements.⁷⁷ In doing so, the MPC created a methodology for categorizing and compartmentalizing the significance of the defendant’s conduct in relation to her understanding and appreciation of the social norms she was rejecting in the course of that conduct. As mental states were placed in a hierarchy, punishments were aligned to reflect the defendant’s degree of culpability, as opposed to merely the damage she may have caused.⁷⁸

Whatever other failings the MPC may have suffered, which I will discuss below, these two innovations were critical. They sought to establish continuity among discussions of culpability by offering generalized definitions of mental states that could be applied across the code and could be definitively linked, albeit imperfectly, to notions of culpability as signaled through punishment. While the MPC has not been adopted by all states, it is influential and has helped to establish norms for culpability that reflect social understandings of blameworthiness.⁷⁹ Perhaps more importantly, studies suggest that jurors are able to apply some, though admittedly not all, of the MPC’s categories of mens rea with relative accuracy and consistency.⁸⁰ This is important not only because the MPC’s concept of mens rea creates the uniformity that common law mens rea lacked, but also because in that uniformity the citizen’s faith in the system is maintained. As a result, the law is a known entity with reliable and discernable parameters.

The MPC makes an additional, critical distinction with its categorization of mens rea: it attempts to differentiate between subjective and objective mental states.⁸¹ Subjective mental states— such as intentionally and knowingly—ask the fact finder to consider what the defendant was actually thinking at the time of his action.⁸² Put another way, they require the state to prove that a defendant actually did intend or know with substantial certainty the harm he was causing at the time of his action. In contrast, the purely objective mental state of negligence asks the fact finder to consider what a like-situated “reasonable” person would have done in the defendant’s situation.⁸³ If the designated mental state is objective, the fact finder considers what the defendant was actually thinking only in relationship to whether or not this thinking accurately mirrors that expected from his reasonable fellow citizens. The mental state of recklessness seeks to meld the subjective and objective approaches, asking fact finders both to consider what the defendant actually understood his situation to be, and then to judge whether, based on this understanding, his actions comported with those of a reasonable man.⁸⁴ The MPC uses these mental state designations to differentiate the defendant’s degree of culpability and so his punishment. The higher levels of mens rea require a higher degree of proof—that is, a demonstration of the defendant’s actual state of mind, independent (in theory at least) of that expected from his fellow citizenry—to impose a higher punishment. The lower levels of mens rea require the state to prove less, but they also authorize lesser punishments.

C. Problems with Mens Rea

While superficially attractive, the MPC’s neat categorization of mens rea between subjective and objective considerations is problematic in that these categories belie the realities of the very process by which they are ultimately applied.⁸⁵ First, the approach rests on a flawed assumption that mental states can be externally discerned. Second, and not unrelated, the law permits the state to prove mens rea through inference. Third, the application of the beyond-a-reasonable-doubt standard introduces a level of inescapable juror-dictated objectivity (or perhaps more accurately, juror-dictated subjectivity) into the calculation of the defendant’s state of mind. I will discuss each of these problematic effects in turn.

Consider first the entwined dilemma of proof with regard to mens rea and the defendant’s obscured state of mind. Even if the MPC’s articulation of mental states accurately reflects social norms and behavioral expectations, this accuracy does little to inform the fact finder of what the defendant was actually thinking.⁸⁶ This, in turn, spawns a related dilemma: the need to allow proof of mental states by inference. Even in the face of high confession rates among defendants,⁸⁷ the state must frequently rely on circumstantial evidence and inference to establish the requisite elements, including the mens rea requirement.⁸⁸

On one level, such reliance on inference is not only logical but is necessary for a functioning justice system. Defendants do not always oblige the state with a confession. Even when a confession exists, the defendant’s own words may themselves appear suspect to the fact finder or may fail to provide insight into her mental state. Regardless, the state is still required either to prove a case beyond a reasonable doubt or to convince a defendant to plead guilty. Without being able to rely on inferences from circumstantial evidence, prosecutors would be asked to complete an insurmountable task in many cases, rendering enforcement of the law more dependent on the ability of the defendant to keep her mouth shut or, having confessed, to convince a jury that her words, once spoken, were faulty, than on any other factor. This in turn might produce an increased incentive for state actors to procure confessions and, having procured the confession, to obscure any suggestion of coercion in that procurement, particularly in high-profile or especially heinous cases. The specter of forced confessions and unscrupulous methodologies of police interrogation is sufficiently fresh in the collective memory—if not an ongoing concern—to suggest that there are social benefits to allowing such inferences from circumstantial evidence.⁸⁹

Beyond this, the acceptance of such inferences is also an acceptance of the very process the jury engages in when it renders a verdict. Whether or not a case actually goes to trial, an advocate, and so the defendant, must contemplate how a fact finder will interpret his actions when overlaid with the law’s proscriptions. Inevitably, this interpretation will require the fact finder to judge what she believes the defendant thought based on what the defendant did. Although the potential inaccuracy of such judgment may temper the interpretation, it cannot stem it altogether.

Even if the prosecutor is able to produce a legally satisfactory confession in a case, or if the defendant elects to speak during colloquy or trial either to protest his innocence or to contest the state’s account of his case, the fact finder must still apply a beyond-a-reasonable-doubt standard to reach a verdict.⁹⁰ The application of the reasonable doubt standard requires the fact finder to consider the evidence in the context of the fact finder’s own knowledge and experience, to interpret the probability of each account, and to reconcile conflicting or incomplete narratives. In this moment of interpretation, the fact finder inevitably lays each account next to her own experiences and makes judgments about veracity based on what seems most likely given what the fact finder knows of, or maybe hopes for, the world. This moment of interpretation is a fraught intersection between the law’s procedural and substantive possibilities.

On the one hand, this moment of interpretation is a communal reclaiming of the law’s very meaning and identity. Most obviously in the context of jury trials—but also before appointed or elected judicial fact finders—the moment the law is applied to the citizen is a moment when the law ceases to be theoretical and static and becomes a living and active body in the lives of the citizenry. No matter the verdict, by going to a jury, the law is interpreted and enforced in a manner that strives simultaneously to shape and respond to social norms. The application of the reasonable doubt standard is a complex and real moment of democracy in which the acceptance or rejection of the law’s province pivots around the doubt of the fact finder.

But if the procedural possibility of the fact finder’s circumstantial inferences is great, the substantive possibility is equally complex and potentially more dire in outcome. As fact finders sift evidence through their own rubrics of experience and expectation to determine their level of doubt, they inevitably reduce even the most subjective of standards to an objective calculus or, perhaps more accurately, to a subjective calculus based on their own subjectivity rather than the defendant’s. Acts are judged and minds are read based on each juror’s expectations fueled by his or her own belief system and experiences. The purchase of a gun, the stalking of a victim, or the discussion of a murder will become evidence of premeditation—or not—because they appear to be so based on what the fact finder believes those same events would mean in the context of his own life. No matter how “truthful” a defendant’s counternarrative may be, if it fails to comport with the fact finder’s own perception of the world, it risks failing as a defense.⁹¹

Even defenses that seek to explicitly account for the defendant’s own experiences inevitably require fact finders to weigh that experience against their own sense of what seems true and what simply does not. In this, all mens rea is inevitably objective (or at least is subjective as to each juror) regardless of the standard articulated. This is surely problematic with respect to subjective mens rea standards; but even in the context of objective mens rea standards, it suggests that the notion of a “reasonable” or “neutral” standard jurors can apply is a myth. In fact, jurors merely overlay their own decision-making processes onto the defendant’s actions. In the process, juror bias, fear, and ignorance are inevitably interwoven into an evaluation of reasonableness.⁹² The juror’s calculation of the defendant’s guilt becomes as much a story about what the defendant did as about the juror’s deceptively complex calculus of what the juror imagines those actions signify. To find the requisite mens rea is to assign a meaning to the defendant’s acts or words and to overlay that assignment with a vision of the law’s own boundaries and prohibitions. It is to remove the law from the realm of the theoretical and to place it not only in the context of the defendant’s life but in the juror’s own life. It is to conceptualize the law in a single moment and in all moments going forward, and in that conceptualization to decide if an action, regardless of the harm it may or may not have created, was criminal, or accidental, or permitted (or ought to be).

In this substantive application, the promise of mens rea as a precise and uniform mechanism to establish culpability inevitably disintegrates, implicating not only the proportionality of the punishment imposed, but also the question of guilt itself. Thus the element of mens rea remains an important tool for distinguishing culpability, but in a different way. Mens rea is recognized as a tool that benefits from fine-tuning,⁹³ and so a new possibility emerges for this calculation to embrace the realities of an individual actor’s cognitive processes.

II. THE COURT, THE LAW, AND THE KIDS

With the general concept of mens rea in place, I now consider the Supreme Court’s development of a jurisprudence of youth. In a trilogy of cases beginning with Roper v. Simmons, the Court has sought to create an Eighth Amendment jurisprudence informed by the age of the offender. The reasoning of this line of cases, while striking new ground in the context of the Eighth Amendment, draws on the Court’s previous treatment of the condition of youth. I begin my examination with the Court’s most recent cases, and then turn to other, frequently noncriminal contexts in which the Court has considered the actor’s youth as a critical factor in its legal analysis. This jurisprudence of youth is premised on the fundamental notion that juveniles in general—and adolescents in particular—are a distinct class of actors, and that distinction carries a legal significance.

A. Youth and the Eighth Amendment

In several recent cases, the Supreme Court has considered the intersection of scientific studies of brain development and the law’s effort to parse culpability in the context of sentencing.⁹⁴ The Court examined questions of sentencing proportionality in light of data regarding the behavioral and cognitive development of particular categories of individuals. In each of these cases, the Court concluded that the Eighth Amendment’s prohibition on cruel and unusual punishment shielded juveniles and the mentally retarded⁹⁵ from certain punishments because they lacked the requisite culpability.⁹⁶ The opinions explained that the identified classes of individuals suffered a failure or deficiency in decision-making processes so significant that it raised sufficient questions about their culpability to render death sentences for both juveniles and the mentally retarded— and sentences of life without the possibility of parole for most juvenile offenders—categorically disproportionate to the defendants’ degrees of blameworthiness.⁹⁷

The Court’s examination of culpability and maturity began in earnest in 1982, even before the proliferation of longitudinal brain studies that mapped juvenile brain development. In Eddings v. Oklahoma,⁹⁸ the Court noted what every parent has long suspected: juveniles do not engage in the same decision-making processes as adults.⁹⁹ The Eddings Court concluded that not only are juveniles less mature than adults, but that they are also more vulnerable to negative influences and outside pressures.¹⁰⁰ In reversing the defendant’s death sentence, the Court reasoned that, from a moral standpoint, it was impossible to equate the failings of a child with those of an adult.¹⁰¹

Later, in Thompson v. Oklahoma,¹⁰² the Court held that the evolving standards of decency contemplated by Eighth Amendment jurisprudence barred the execution of defendants who were under the age of sixteen at the time they committed their offense.¹⁰³ The Court held that this category of juveniles should be spared this punishment, even though it could be constitutionally imposed on an adult, because these juveniles lacked the experience, education, and intelligence of adults.¹⁰⁴ It noted that juveniles were less capable of evaluating the consequences of their actions and also more apt to be motivated by their emotions and peer pressure.¹⁰⁵ As a result, the Court concluded that, even when they engaged in conduct that would otherwise qualify them to receive the death penalty, such juveniles were not as culpable as adults, and therefore evolving standards of decency meant that the Constitution barred their execution.¹⁰⁶ In short, according to the Thompson Court, “[t]he reasons why juveniles are not trusted with the privileges and responsibilities of an adult also explain why their irresponsible conduct is not as morally reprehensible as that of an adult.”¹⁰⁷

A year later, in Stanford v. Kentucky,¹⁰⁸ the Court seemed to back off the conclusion, though not the legal standard, that it had articulated in Thompson. In Stanford, the Court concluded that it was in fact permissible to execute sixteen-year-old offenders because state legislatures, not the Court, determined standards of decency.¹⁰⁹ The absence of a clear national consensus prohibiting the application of capital punishment to juveniles left it to the states to determine the minimum age for execution.¹¹⁰ Even in this retreat, the Court required the minimum execution age to be at least sixteen based on its conclusion in Thompson that the ultimate penalty of death required a correspondingly ultimate demonstration of culpability—one absent in those younger than sixteen.¹¹¹

In 1993, the Court again revisited the question of the effect of youth on culpability and proportionality of punishment. In Johnson v. Texas,¹¹² the Court concluded that the age of the offender was a relevant mitigator in sentencing determinations.¹¹³ The Court noted in particular that “[a] lack of maturity and an underdeveloped sense of responsibility are found in youth more often than in adults and are more understandable among the young.”¹¹⁴ The Court continued, “These qualities often result in impetuous and ill-considered actions and decisions.”¹¹⁵ These traits, while rendering the child dangerous and his decision-making poor, are also transient—and likely to subside as the child matures.¹¹⁶ As a result, the offender’s youth should counsel toward leniency and diminish our concept of his culpability.¹¹⁷

While these early cases did not have the benefit of modern neuroscientific studies, discussed in greater detail in Part III, and did not categorically overturn punishments for juveniles over the age of sixteen, they laid the critical groundwork for the Court’s more recent decisions linking notions of culpability to cognitive development. These subsequent cases, and the studies they relied upon, are both a continuation and confirmation of the line of Eighth Amendment reasoning the Court began two decades ago: when we speak of criminal culpability, children are fundamentally different than adults.

In 2002, the Court returned to the question of cognitive development and culpability in a different context. In Atkins v. Virginia,¹¹⁸ the Court held that the Eighth and Fourteenth Amendments prohibited the execution of mentally retarded persons.¹¹⁹ Atkins overturned the Court’s previous ruling in Penry v. Lynaugh,¹²⁰ which had held that the Eighth Amendment did not mandate categorical exemption from the death penalty for mentally retarded offenders.¹²¹ Penry had held that it was improper to exclude mentally retarded individuals as a class from achieving the level of culpability necessary to justify the imposition of the death penalty.¹²² In Atkins, however, the Court did an about-face; evolving standards of decency had shifted, rendering the execution of the mentally retarded excessive punishment and thus in violation of the Eighth Amendment’s prohibition on cruel and unusual punishment.¹²³

At first blush, Atkins may appear to be an outlier in a piece about culpability standards among juvenile offenders. After all, the Atkins Court considered the underlying culpability and resulting eligibility for execution of those with a diagnosis of a permanently (or near permanently) deficient intelligence. Unlike juveniles, the intellectually disabled do not age out of their immaturity or myopic decision-making processes. Despite this admitted—and from the perspective of punishment theory, significant—difference, Atkins nevertheless informed the Court’s subsequent rulings with regard to juvenile culpability because of its reliance on scientific research.

In Atkins, the Court defined culpability in terms of the offender’s state of mind, or his inability to achieve the requisite state of mind.¹²⁴ Intellectually disabled individuals were judged less culpable because they suffered from a deficient cognitive and behavioral development.¹²⁵ Beyond this, in terms of punishment theory, these mental deficiencies rendered the death penalty ineffective as a deterrent for the intellectually disabled and inappropriate as a means of achieving retribution.¹²⁶ While the Court admittedly did not reach the question of what an offender’s mental retardation would signal with regard to his actual state of mind, the Court nonetheless relied heavily on cognitive and behavioral research to determine that, despite its early holding in Penry, the Eighth Amendment precluded the execution of the mentally retarded based on their reduced culpability as a class.¹²⁷ Atkins relied on scientific research to establish a constitutional standard determined not by an individualized analysis of actors’ abilities or understandings, but by precluding particular categories of actors from achieving the mens rea necessary to achieve the highest levels of culpability. This reliance rendered the Court’s decision in Atkins a critical precursor to the question it would confront three years later in Roper v. Simmons.

Like Atkins, the Court in Roper returned to the question of whether the Eighth Amendment precluded the execution of a category of individuals—this time, juvenile offenders.¹²⁸ In Roper, despite Justice O’Connor’s protestations,¹²⁹ the Court concluded that there was no need for an individualized assessment of an offender to conclude that the death penalty for juveniles was cruel and unusual.¹³⁰ Citing scientific evidence, the Court stated that the differences between juvenile and adult offenders were “too marked” and “well understood” to require individual analysis.¹³¹ Juveniles were simply categorically less culpable than adult criminals.¹³² Their lack of fully formed identity,¹³³ their lack of control,¹³⁴ and their incomplete cognitive and behavioral development¹³⁵ all led the Court to conclude that the behavior of juveniles could not be equated to that of their adult counterparts.¹³⁶ And so, as in Atkins, the Court in Roper found that as a matter of punishment theory, the death penalty failed to serve its permissible purposes and was therefore constitutionally prohibited for juveniles.¹³⁷

In the subsequent cases of Graham v. Florida and Miller v. Alabama, the Court used similar evidence and logic to conclude that sentencing juvenile offenders to life without parole for nonhomicide offenses after a sentencing hearing¹³⁸—and automatically for homicide offenses¹³⁹—violated the Eighth Amendment’s prohibition on cruel and unusual punishment. Like in Roper, the Court in both cases rejected the states’ arguments that sentencing courts adequately considered the individual juvenile’s culpability in imposing sentencing.¹⁴⁰ Instead, the Court concluded that the punishments were categorically inappropriate for juvenile offenders given scientific knowledge of juvenile decision-making processes and cognitive development. In Graham, the Court acknowledged that while “[c]ategorical rules tend to be imperfect, . . . one is necessary here.”¹⁴¹ The Court noted that juveniles suffer a “lack of maturity and an underdeveloped sense of responsibility” and that as a whole they “are more vulnerable or susceptible to negative influences and outside pressures, including peer pressure.”¹⁴² The Court went on to state that “developments in psychology and brain science continue to show fundamental differences between juvenile and adult minds.¹⁴³ For example, the parts of the brain involved in behavioral control continue to mature through late adolescence.”¹⁴⁴ In short, the Court concluded that certain punishments were inappropriate given the inability of the juvenile defendant to achieve the requisite level of culpability because of the effect of his age upon his cognitive development.

B. The Jurisprudence of Youth

While these most recent Eighth Amendment cases struck down previous decisions, they hardly broke new ground. Each of these cases follows a doctrinal principle articulated in other areas of the law: that immaturity may trigger legal protections, restrictions, or both for children that the law does not impose on adults.¹⁴⁵ As the Court itself noted in Roper, juveniles cannot vote,¹⁴⁶ serve on juries,¹⁴⁷ or marry without parental consent.¹⁴⁸ Additionally, they cannot consent to sexual intercourse.¹⁴⁹ In many states, juveniles cannot terminate a pregnancy without parental or judicial consent.¹⁵⁰ And while judicial¹⁵¹ and legislative¹⁵² trends grant minors comparatively more access to contraception without parental consent than to abortion, in 2006 the Food and Drug Administration deviated from this trend and limited access to Plan B for minors.¹⁵³ Likewise, juveniles cannot obtain tattoos or ear piercings without their parents’ permission, or, in some jurisdictions, at all.¹⁵⁴ They cannot buy tobacco products¹⁵⁵ or alcohol¹⁵⁶ or, in some jurisdictions, even be present in locations where alcohol is served.¹⁵⁷ Juveniles cannot join the military¹⁵⁸ or voluntarily discontinue their educations.¹⁵⁹ They cannot be elected to Congress¹⁶⁰ or the presidency.¹⁶¹

Minors are not prohibited from executing contracts, but as a general rule, contracts made by minors are voidable.¹⁶² Likewise, minors have a right to acquire and to own property, but the law presumes the minor incapable of managing the property himself; for that she must seek out the assistance of an adult, often court-appointed, guardian.¹⁶³ Minors cannot initiate or defend against lawsuits.¹⁶⁴ They cannot even declare themselves emancipated from their parents without first demonstrating to a court that they are the “exceptional juvenile,” or perhaps that their home situation is sufficiently dire that they should be allowed to deviate from the norm and remove themselves in the interests of their very survival.¹⁶⁵

In other contexts, the Court has acknowledged juveniles’ particular vulnerability by subjecting them to the patronizing ignominy of state-imposed curfews¹⁶⁶ and protecting them from state-imposed prayers at graduation ceremonies¹⁶⁷ or high school football games.¹⁶⁸

Recent decisions in the realm of substantive and procedural criminal law further expand the jurisprudence of youth. In 2011, a year after the Court’s decision in Graham and the year before Miller, the Supreme Court once again considered brain science—this time in the context of the Miranda¹⁶⁹ custody analysis.¹⁷⁰ In J.D.B. v. North Carolina, the Court held that the test for determining whether or not a juvenile was in custody or was free to terminate contact with the police must be evaluated based on what was reasonable for a juvenile, rather than what was reasonable for an adult.¹⁷¹ The case concerned J.D.B., a thirteen-year-old middle school student who was removed from class and interrogated in a closed-door conference room by four adults, including a uniformed police officer and School Resource Officer.¹⁷² At trial, J.D.B. moved to suppress statements made during the interrogation on the grounds that he had not been administered the Miranda warnings.¹⁷³ In response, the State successfully argued that J.D.B. was not in custody because a reasonable person would have felt free to leave the conference room; therefore no Miranda warnings were necessary.¹⁷⁴ Writing for the majority, Justice Sotomayor reasoned that a child suspect’s age was relevant to determining whether or not he reasonably believed he was free to leave and so was relevant to the necessity of the Miranda warnings.¹⁷⁵ Citing brain science data similar to that discussed in Graham,¹⁷⁶ the Court noted that the risk of coercion is “all the more acute” during youth.¹⁷⁷ Accordingly, law enforcement officers and courts must take the suspect’s youth into account in determining whether or not Miranda should be administered.¹⁷⁸

From prayers before high school football games, to the sale of alcohol, to the custody analysis for Miranda, the list goes on, in competing (and at times seemingly contradictory) iterations. But in the end all the restrictions and protections acknowledge a fundamental reality that we all seem to know and accept, and that the study of the brain has now confirmed: children are different than adults.

III. THE SCIENCE OF ADOLESCENCE AND WHAT IT MEANS FOR CULPABILITY

But what exactly does the scientific evidence show? In the last two decades a burgeoning body of scientific data has emerged that has bolstered the Court’s recent decisions regarding adolescent culpability in the context of sentencing. This literature provides critical insights into the thought processes and cognitive abilities of adolescents.

I will begin the discussion of this scientific evidence with a brief overview of the juvenile justice system and its articulated and divergent goals. While not all juveniles are tried in the juvenile court system—indeed the continuing trend is to try juveniles in the adult court system—the creation of an independent juvenile system itself signals a recognition that youthful offenders are categorically different from adult offenders. Juvenile systems have cabined the effect of this acknowledged difference primarily to the provision of pretrial services and modified sentencing regimes.¹⁷⁹

With some knowledge of the juvenile justice system in place, I turn from the system to the scientific literature. The studies vary widely, but, as a general principle, they conclude that adolescents as a class operate under a comparatively reduced capacity when it comes to higher executive function, including autonomous choice, risk perception, self-management, and calculation and comprehension of future consequences.¹⁸⁰ This deficiency not only renders adolescents more likely to engage in risky behavior than adults, but also to have a more myopic understanding of the external effect of that behavior than adults.¹⁸¹ Perhaps more significantly these studies conclude that this deficiency is the norm, not an aberration, in the adolescent population.¹⁸² In other words, unlike evidence of a mental defect or abnormality that supports a reduction in culpability because of its very deviation from the norm, evidence of adolescent thought processes establishes an appropriate mens rea baseline that differs significantly from the adult perspective criminal law has come to rely on. In Part IV, I will explore further what this suggests for a mens rea analysis.

Psycho-social literature explains that adolescence is a transitory period in which the individual’s very identity and character develop and coalesce.¹⁸³ As a result, adolescents are more prone than adults to engage in explorative and experimental behavior that seeks to test or push previously established social boundaries—including legal ones.¹⁸⁴ The transitory nature of the development period, however, suggests that such behavior will usually dissipate as the adolescent ages and develops into an adult.¹⁸⁵ In short, youthful offenders do not always or necessarily become adult offenders.

A second, more recent body of scientific literature builds on these psycho-social conclusions, examining the biological and neurological realities of the adolescent development period.¹⁸⁶ Such studies suggest that there may be a biological explanation for the behavior described in the psycho-social literature, offering a more nuanced examination of how the physical maturation that occurs during adolescence may affect social maturation and executive function.¹⁸⁷

At the end of the day, the literature surrounding adolescent development reveals that teens engage in a different decision-making process than adults on a variety of levels. This difference is peculiar to adolescents and affects their understanding of choices and consequences, including those that may carry legal implications. As a result, these studies are relevant not only to a calculation of proportional punishment as it relates to the youthful actor’s culpability, but also to calculations of mens rea as a signifier of culpability.

A. The Juvenile Justice System

In many ways, the creation of a separate system to adjudicate juvenile offenders at the turn of the twentieth century was the product of the reform movement that recognized the difference between adults and juveniles even before the scientific literature had begun to define the parameters and sources of that difference.¹⁸⁸ At its inception, this new juvenile justice system was premised on the notion that children were different than adults, even when they engaged in “adult-like” criminal behavior. Early juvenile justice systems focused on rehabilitation rather than punishment and took the view that criminal conduct in children was a symptom of poverty and poor parental supervision.¹⁸⁹ The immaturity of the offender was important to the focus on rehabilitation. Not only did immaturity indicate a difference in capacity from adult defendants,¹⁹⁰ but it also signaled a corresponding reduction in the level of culpability that required alternative procedures for assessing guilt and sentences.¹⁹¹

As the procedures and purposes of the juvenile court system shifted with the Court’s decision in In re Gault,¹⁹² so too did the premise that the juvenile system should rehabilitate youthful offenders and thereby save them from a life a crime.¹⁹³ As the juvenile system increased its procedural resemblance to its adult counterpart, so too did it increase its reliance on punitive sentencing regimes that sought to hold young offenders accountable for their actions.¹⁹⁴ In short, during the “new,” post-Gault era of juvenile justice, while the offender’s youth and immaturity may still have factored into sentencing,¹⁹⁵ juveniles were viewed as having the requisite moral judgment and self-control to be held responsible for their criminal acts like their adult counterparts.¹⁹⁶ Minors were still viewed as less blameworthy than adults due to a variety of developmental factors,¹⁹⁷ but the focus of juvenile systems shifted toward public protection and the need for punishment.

In the past two decades, this trend produced a juvenile system less likely to assert jurisdiction over adolescents who commit violent offenses or who are repeat offenders198 and more likely to impose sentences commensurate to those imposed on adult offenders.¹⁹⁹ Until the Court’s pronouncement in Roper, even as courts took youth into account as a mitigating factor, juveniles were still treated as nearly indistinguishable from their adult counterparts and sentenced accordingly.²⁰⁰ Even Roper and its progeny, while focusing on the documented differences between adult and juvenile offenders, confined the impact of this difference to an assessment of culpability for sentencing.²⁰¹ The designation of criminal culpability contained in the mens rea element of the offense remains untouched by the Roper line of cases. Whatever immaturity a youthful offender suffered and whatever corresponding sentencing mitigation this may warrant, his guilt was, and is, still determined using the same culpability standard applied to adults.

B. The Scientific Literature

Beginning in Roper, the Court began to rely—tentatively at first—on a burgeoning body of scientific literature to support the notion that children were different than adults.²⁰² By the time the Court rendered its opinions in Graham and Miller, scientific evidence had assumed a more central role in the Court’s Eighth Amendment analysis; children were fundamentally different than adults, and this fundamental difference rendered them less culpable, at least for the purposes of punishment. As discussed above, such conclusions were hardly novel given the Court’s overall jurisprudence of youth or, indeed, the states’ construction of a distinct system of juvenile justice. What was unique was the Court’s consideration of scientific data to support what the Roper Court suggested was an intuitive conclusion—children were different, and the difference carried legal significance.

This Section offers an overview of the scientific data that informed the Supreme Court’s recent decisions, as well as new data that have developed since. This evidence, like all evidence, is not without its limitations and challenges. In Part IV, I will consider how these data can and should inform assessments of mens rea, as well as the proof problems such data may present as an evidentiary matter.

1. What We Know

Even the recognition of adolescence as a distinct period of development from childhood or adulthood is both recent and significant.²⁰³ As a developmental period, adolescence extends from puberty to the early twenties and is a critical and often volatile bridge between childhood and adulthood.²⁰⁴ During this period, teens are more likely both to underappreciate risk and engage in reckless behavior.²⁰⁵ As researchers attempt to answer the critical question of why adolescents engage in risky behavior, they map not only the psychological development of their subjects, but also their physical development.²⁰⁶ While such research is relatively nascent and leaves many questions unanswered, an important reality for criminal law emerges: the reckless behavior and curtailed decision-making processes of adolescence are the hallmarks of normal development, not a defect, and they distinguish adolescents from adults.²⁰⁷ This is not to say that adolescents lack free will, but it is to say that they engage in different decision-making processes than adults. In this light, the risky behavior of adolescence, including criminal behavior, is recast as an important stage of normal development that allows individuals to understand socially created boundaries and to live within them.²⁰⁸

Generally, and not surprisingly, studies of adolescence reveal that teens as a class are less competent decision makers than adults.²⁰⁹ To paraphrase the Roper Court, this hardly comes as a surprise to anyone who has ever had any contact with a teenager. What renders these studies more than mere prophecies of the obvious is that they provide tangible insight into why teens are less competent decision makers. Whatever question one may have about their usefulness in the legal realm,²¹⁰ there is no denying their increasing influence on the Court at least with regard to questions of law.

From these studies some salient themes emerge. Compared to adults, adolescents demonstrate deficiencies in their capacity for autonomous and consistent choice,²¹¹ self-management,²¹² risk perception,²¹³ and the calculation of future consequences.²¹⁴ They are more likely to take risks²¹⁵ and to be sensation seeking.²¹⁶ They are more vulnerable to peer influence²¹⁷ and display heightened responses to rewards.²¹⁸ Their personalities and character are in flux.²¹⁹ Even in mid-adolescence, as teens’ cognitive capacities approach those of adults, they are less skilled than their adult counterparts in using these capacities to make real-life decisions.²²⁰ These “deficiencies” in comparison to adults are not defects, but the products of normal physiological and psychological development during the adolescent period.²²¹ As one researcher concluded, the teen brain is not defective, but “sculpted by both biological and experiential factors to adapt to the unique social, physical, sexual, and intellectual challenges of adolescence.”²²² While the timing and the trajectory of development vary among individuals, the characteristics consistently manifest across the class.²²³ The Court in Graham and Miller found the characteristics to be sufficiently pervasive to justify categorically excluding one punishment and categorically forbidding mandating another.²²⁴ Likewise, individual variance notwithstanding, these characteristics are distinct and unique to this period of development, contributing to immature judgment²²⁵ and an increased process of exploration and experimentation that may include criminal activity.²²⁶ In short, if adolescence is characterized as a period of rapid change and development, what distinguishes it most obviously from childhood or adulthood is that it is also a time of boundary-pushing and reckless behavior.

This is hardly breaking news. The wild and thrilling ride of youth is a glorified and much-documented rite of passage that seems to defy cultural and geographic boundaries.²²⁷ Developmental psychologists over the years have offered a variety of explanations for this tendency toward risky behavior,²²⁸ but recent advances in neuroimaging techniques have fueled a new wave of scientific exploration that builds on these existing adolescent development theories to suggest a biological basis for such behavior.²²⁹ In particular, longitudinal MRI studies have not only tracked the structural development of the brain, but have demonstrated that the brain continues developing well into early adulthood.²³⁰ In particular, researchers note that the frontal cortex—seat of the powers of executive decision-making, coordination of emotions and cognition, goal driven planning, forethought, and impulse control—is the last to achieve structural maturity.²³¹

MRI studies have also revealed that myelination, the insulation of neural axons with a fatty substance known as white matter, increases linearly from childhood to adulthood.²³² With this increase comes a corresponding progression of fast and efficient communication among brain systems.²³³ Adolescence also marks a period of pruning of grey matter—the uninsulated cell bodies and synapses of the brain.²³⁴ If the period of preadolescence is marked by a rapid development in the volume of grey matter, adolescence is notable as a period of change in which the volume and density of this matter decrease.²³⁵ This dual process of myelination and pruning of grey matter is critical to create more efficient communication between different parts of the brain.²³⁶ These combined processes allow the adult brain to function quickly and efficiently.²³⁷ It is clear that this development continues throughout adolescence.²³⁸ What is less clear is how this physical immaturity affects behavior or, from the perspective of criminal law, precisely what impact it has on decision making processes.

It is also clear from the emerging research that the development from childhood to adulthood, including the period of adolescence, is transitory and continual.²³⁹ As children grow, so too does their cognitive control.²⁴⁰ An individual’s basic elements of decision making—including understanding and reasoning—increase throughout childhood and into adolescence.²⁴¹ Likewise, the development of connective circuitry through myelination from the prefrontal cortex and other parts of the brain continues through adulthood. This change not only facilitates effective decision-making, but it creates flexibility in the regulation of impulses and decisions.²⁴² Prefrontal connections that emerge in adolescence strengthen into adulthood.²⁴³ In short, as children mature, so too do their basic information-processing skills along a somewhat steady continuum to adulthood.

But there are also some developmental findings that are specific to adolescents, and in the detail of that specificity may lie the devil of adolescent thought. Adolescents display heightened brain responses to socially relevant cues.²⁴⁴ Paradoxically, and perhaps cruelly, this heightened sensitivity to social cues does not render adolescents more capable of meeting new social challenges; instead it appears that this sensitivity makes them more subject to peer influences and pressures.²⁴⁵ In addition, adolescents exhibit a heightened response to rewards or sensations that seems to dissipate or at least diminish by adulthood but is also more pronounced than during childhood.²⁴⁶ The emerging image of adolescence as a period is one of competing neural and psychological tensions and interactions.²⁴⁷ As the identity and the brain develop, they do so on trajectories that may ultimately culminate in adulthood’s mature thought processes and cognitive abilities, but along the way, distinct functions and paths of development may drive the brain and the neural systems.²⁴⁸

As the Court reconsidered its Eighth and Fourth Amendment jurisprudence with regard to youth, these studies painted a murky image of adolescence. Any discussion of teen behavior inevitably starts with the easily observable and well-documented reality that adolescents engage in riskier behavior than adults. The more difficult question, and from the perspective of criminal law the more relevant question, is why? Emerging research attempts to answer that question, at least in part, and offers a variety of competing and complimentary theories. Ultimately, what makes this scientific evidence important is that it suggests not only that there is a neurological and psychological explanation for this behavior but also that the behavior is transitory and a necessary component of development into adulthood. In short, to borrow from Patti Smith, even the most unruly kids may be all right in the end; they are just kids.²⁴⁹

2. What We Don’t Know (or the Limits of Science)

As many scholars have cautioned, there are limitations to the usefulness of neuroscience in criminal law, and courts have been quick to recognize those limitations.²⁵⁰ First, and perhaps most critically, while generalizations and trends can be recorded, neuroscience offers little insight into individual behavior.²⁵¹ At least in the context of Eighth Amendment jurisprudence, this lack of individualized accounting has not bothered the Court.²⁵² As the Court noted repeatedly in the Roper line, the noted behavior and developmental trends were sufficiently consistent and well documented to forgo an individualized analysis and to permit a categorical prohibition of the considered punishments.²⁵³

Nonetheless, the Court’s acceptance of a category-based analysis may prove more challenging in the context of substantive criminal law for another reason. Studies not only note the variance among adolescents but also note that biological or neurological realities may not exclusively control behavior.²⁵⁴ For example, while functional imaging studies consistently revealed that adolescents lacked fully mature brains, others suggested that adolescents tended to employ different brain processes than adults in carrying out identical tasks.²⁵⁵ However, interpreting the behavioral implications of these studies does not always yield concrete conclusions about the juvenile brain.²⁵⁶ Not unrelatedly, studies have shown that while physical maturation of the brain extends well into early adulthood, by mid-adolescence the difference in decision-making between teens and adults in lab-like settings appears to diminish to the point of near irrelevance.²⁵⁷ Moreover, these findings may be discounted by more recent studies demonstrating that, when placed in settings in which adolescents are subject to peer pressure or requirements for rapid decisions, they appear to make riskier, less well-conceived choices than adults, but these studies also render any categorical conclusion more complex.²⁵⁸

Whether because of these inconsistencies, or perhaps some greater reluctance to use such category-based assessments to determine factual questions, courts have been reluctant to rely on neuroscience outside of sentencing mitigation.²⁵⁹ In those rare instances in which the courts have used neuroscience outside of sentencing, scholars have noted confirmation bias—the process by which the fact finder uses the evidence to confirm preconceptions about the defendant, rather than to acquire some new understanding.²⁶⁰

There is no denying the cataloged shortcomings and unanswered questions of the science. Likewise, time and time again, lower courts have remained unmoved in the face of scientific evidence challenging the transfer of juveniles to adult courts,²⁶¹ the imposition of adult sentences,²⁶² and the application of adult-calibrated mental states to juveniles.²⁶³ Others have argued that this rejection counsels against the usefulness or relevance of neuroscience in an assessment of mens rea, and that it counsels a conservative and circumspect approach to scientific advocacy in the courtroom.²⁶⁴ As I will discuss in Part IV, however, logic and justice counsel otherwise.

IV. THE NEXUS OF NEUROSCIENCE AND MENS REA

As an element, mens rea distinguishes behavior and assigns culpability.²⁶⁵ To accomplish this goal, mens rea must contemplate the actor’s state of mind at the time of her act—not in the abstract but in actuality. It must consider what the defendant thought or understood her actions to mean. Admittedly, this is a complex analysis requiring fact finders to infer and discern mental states from a defendant’s actions. In this process, fact finders construct their notions of the defendant’s mens rea as much from their own thought processes as from what they know of the defendant’s behavior. They anchor their judgment of the defendant’s culpability in their own adult decisionmaking processes.

From the perspective of juvenile offenders, this grounding of mens rea in an adult-referenced standard distorts the thought processes that adolescents actually engage in. Therefore, while an adolescent offender may not be deemed as culpable as an adult for purposes of punishment, he may nonetheless be judged culpable, or guilty, in the first place based on his ability (or more accurately his inability) to conform to adult expectations and understandings of the social norms that undergird criminal law generally and mens rea particularly.

This is problematic. If mens rea seeks to demarcate culpability with precision and consistency, then it must accurately reflect what the defendant understood and the cognitive methodology she engaged in when arriving at that understanding. The Court has acknowledged as much in its Eighth Amendment jurisprudence.²⁶⁶ Its failure to extend such logic to the element of mens rea creates a gap between the articulated goal of mens rea and the reality of its application to youthful offenders. For the mens rea element to serve its designated role in the criminal justice process as the measure of guilt, it must reflect the mental state, with all its comparative cognitive deficiencies, of the adolescent it considers.

To rely on an adult mens rea standard for youthful offenders in the face of scientific evidence demonstrating that such offenders do not possess the same cognitive abilities or engage in the same thought processes as an adult is to undermine mens rea’s value. It effectively reduces mens rea to a wholly objective analysis that fails even to use a properly objective standard of comparison. Whatever shortcomings remain in the current state of scientific knowledge, one principle remains clear: children are different from adults, and so the calculation of their mens rea must be different.

In rejecting attempts to apply neuroscience as a basis to alter the mens rea analysis for juveniles, some courts have contended that such an alteration would require a legislative change to the criminal code and therefore exceeds the scope of judicial power.²⁶⁷ For example, in State v. Heinemann,²⁶⁸ the trial court declined to include a jury instruction on how adolescent decision-making might affect the reasonableness of the sixteen-year-old defendant’s actions.²⁶⁹ Heinemann is interesting in that the defendant’s requested instruction did not mention brain science, but did request that the jury “consider the age of the defendant, . . . specifically, the level of maturity, sense of responsibility, vulnerability and personality traits of a sixteen year old, when deciding his defense of duress.”²⁷⁰ It appears that Heinemann did not present any scientific evidence to support these conclusions in his trial, though there is no indication as to whether or not he attempted to do so.²⁷¹

In upholding the lower court’s decision, the Supreme Court of Connecticut “acknowledge[d] that juveniles often have more immature decision-making capabilities and recognize[d] the literature supporting the notion that juveniles are more vulnerable to all sorts of pressure, including but not limited to, duress.”²⁷² However, the court reasoned that granting the defendant’s requested instruction would “require this court to rewrite the entire Penal Code.”²⁷³ In short, the court concluded that the legislature’s decision to allow a sixteen-yearold defendant to be tried in adult court and its failure to indicate an alternative mens rea standard to be used for him during that trial signified that he should be treated as any other defendant and so be denied the instruction.²⁷⁴

It is hard to tell from Heinemann if the court would have been more willing to allow this instruction had the defendant not been tried in adult court or had he presented evidence—even some universal evidence—to support the claims asserted in his instruction. These difficulties aside, the logic of the court’s deference to the legislature in denying the instruction reflects a more fundamental misunderstanding of the concept of mens rea itself. As discussed in Part I, mens rea serves a critical role in criminal law by defining and categorizing culpability according to a defendant’s state of mind. Interwoven into the very concept of mens rea is an acknowledgement of the defendant’s thought processes and cognitive function. Accordingly, the governing legislation has already constructed a legal standard that would encompass the proposed consideration of adolescent-specific cognitive processes.²⁷⁵ For courts to allow testimony regarding an adolescent defendant’s development, therefore, would not contemplate a legislative modification, but simply the proper consideration of the existing element.

The U.S. Supreme Court’s decision in J.D.B. supports this notion. In J.D.B. the Court noted that the suspect’s age is a relevant component of the objective custody analysis, as it would affect “how a reasonable person in the suspect’s position ‘would perceive his or her freedom to leave.’ ”²⁷⁶ While the Miranda decision did not differentiate between adult and child suspects, in J.D.B. the Court found the cognitive attributes and characteristics of juveniles to be sufficiently distinct as to require a standard of reasonableness that acknowledged and accounted for this difference.²⁷⁷ In short, the silence of the standard itself did not undo the pervasive reality that teens process information and arrive at conclusions in ways that are not only dictated by their immaturity and their level of development, but in ways that are different than those of adults.²⁷⁸

In the context of juvenile offenders, neuroscience confirms that adolescents demonstrate cognitive processes that are distinct from adult cognitive processes. These studies reveal that teens consistently and almost routinely engage in behavior that increases their risk of death or harm,²⁷⁹ and that such risky behavior is a product of inefficient and underdeveloped cognitive processes that may decrease as the adolescent’s prefrontal cortex matures and the child becomes an adult.²⁸⁰ The Supreme Court has repeatedly acknowledged that this immature development is sufficiently pervasive to justify treatment of adolescents as a class for purposes of both Eighth Amendment culpability²⁸¹ and Miranda custody analyses.²⁸² More broadly, this developmental immaturity suggests not only that a reasonable decision made by an adolescent may be patently unreasonable to an adult, but also that a given action may signal one state of mind if taken by an adult and quite another if taken by a child. For purposes of an objective state of mind analysis, as the Court concluded in J.D.B.,²⁸³ the reasonableness of any particular decision must be calculated from the perspective of the defendant—the one who made the decision in the first place. For purposes of a subjective state of mind analysis, which will invariably require the fact finder to draw inferences, the defendant’s decisions and actions must be judged in light of what the defendant understood them to signify.

Given the criminal law’s treatment of mental state as a measure of culpability²⁸⁴ and our knowledge of the juvenile brain,²⁸⁵ it is insufficient to use such knowledge only to mitigate punishment or to adjust a Fourth Amendment standard of reasonableness. Such a limitation fails to address the underlying dilemma that the assessment of guilt was flawed in the first place through the use of an adult-based mens rea standard. Indeed, nothing in the Court’s jurisprudence of youth or in the emerging neuroscience suggests that a one-size-fits-all mens rea standard is appropriate.

To recognize that adolescent brain science is relevant to mens rea, however, invites the practical question of what precise role such science should play in the litigation of a particular criminal case. This is a problem with no easy solution. The proof or disproof of elements in a criminal case is a choreographed display premised on the notion that the competing narratives of prosecution and defense should be tailored and confined to ever-narrowing circles of relevancy. In the context of brain science, as discussed above, additional limitations may present themselves.²⁸⁶

Despite these limitations, at a minimum, what is currently known from the scientific literature suggests two courses of action. First, to achieve an accurate assessment of mens rea for juvenile offenders, courts may not need to alter state of mind terminology, but they do need to alter the perspective through which that terminology is interpreted in order to account for differences between juvenile and adult thought processes. Second, while the Supreme Court is right that there is a fundamental and understood difference between adults and juveniles, the analysis offered in the Roper line and in J.D.B. should be extended to mens rea as this analysis is applicable but is, by itself, insufficient to support the mens rea element’s full function.

At the most basic level, J.D.B. and the Roper line examined the significance of juvenile status as a matter of law with regard to whether or not the protections of the Fourth and Eighth Amendments required wholesale recalibration for adolescent offenders or suspects.²⁸⁷ To speak of a mens rea analysis, however, is to speak in terms of matters of fact and the interpretation of those facts in the face of what the law requires or prohibits. In this, while a fact finder may be able to recognize a difference between her behavior as an adult and her behavior as a juvenile, in assessing mens rea her task is more nuanced—she must not only recognize the difference, but also the basis of the difference and the significance of the offender’s behavior in light of those differences. Put another way, it is a different job to consider whether or not a child is different than an adult (either for punishment purposes or determination of custody status) than to consider how an adolescent’s actions should be interpreted given what is known about adolescent thought processes. An adult may be able to intuitively recognize that her adult self is different than her juvenile self, but she may not be able to remember or even be aware of the thought processes she engaged in as an adolescent. This requires a more nuanced understanding that may well defy ordinary knowledge and memory. Here lie the devilish details. This nuanced understanding of the state of mind is critical to the function of mens rea as articulated by substantive criminal law— to weigh the offender’s actual, as opposed to imagined, state of mind—and it may require guidance to achieve.

As a practical matter, different possibilities emerge to accomplish mens rea’s function as applied to youthful offenders. Most obviously, such a defendant could seek to present individualized evidence of his own thought processes and cognitive function. If a defendant can access the resources to support such an evaluation, and it supports his defense, this evidence would seem relevant to factual question of mens rea. Allowing a defendant to present such evidence, however, should not be confused with requiring a defendant to undergo a brain scan in order to successfully mount a science-based defense that challenges the state of mind element.²⁸⁸ Such a forced examination not only raises Orwellian-like privacy concerns, but seems odd given that such an examination would be used to demonstrate the utter normalcy of the adolescent defendant—as opposed to his deviation from the norm or any dangerousness or deficiency that may accompany such deviation.

Given the Court’s willingness in the Roper trilogy and J.D.B. to accept youthfulness as a universal category—a willingness supported by the scientific literature—another possibility is that juvenile defendants should be allowed to present universal neuroscientific evidence that would demonstrate the traits that “average” or most juveniles at a like stage of biological development would possess. This evidence would be akin to that considered by the Court in the Roper line (and with regard to intellectual disability in the Atkins line).289 While such universal evidence would admittedly provide limited insight into the particular defendant’s thoughts, it would serve as a baseline from which fact finders could test the reasonableness of their own interpretations of the defendant’s actions as it relates to her mens rea, while avoiding the constitutional and ethical concerns of a “forced” neuroscientific examination in order to demonstrate that the defendant was in fact an ordinary teenager (at least as far as his thought processes go). In addition, by providing the fact finder with an informed perspective with regard to juvenile thought processes and linking that perspective to the mens rea calculation specifically, the risk of confirmation bias may be reduced—although such bias is a risk even in ideal circumstances.²⁹⁰

Such a reliance on universal evidence to demonstrate inclusion in the norm may raise the question of relevance, or even necessity. Here the Court’s own assessment of the fundamental difference between adults and juveniles is instructive. All fact finders, by legal definition, are adults.²⁹¹ They are older than the juvenile offender at the time of the offense in question. As a result, their own baseline differs from the relevant baseline of the adolescent they are tasked with judging. The adolescent’s baseline therefore must be established and cannot be presumed to be understood or even remembered in ways that it might be for an adult offender.

As important as such universal evidence is, it is not without problems. It assumes both a uniformity of cognitive development that can be determined from the subject’s age and that the presence of such uniformity will produce discernable and traceable conclusions for the situation the fact finder must now contemplate.²⁹² It is simply not correct that all sixteen-year-olds who drive drunk universally understand some reality to be true or universally fail to appreciate some risk—every single time, all the time. While the literature suggests that some uniformity exists, it also demonstrates both developmental variance internal to any given juvenile and the significant impact that variances in external stimuli can have on juvenile subjects.²⁹³

These limitations do not counsel discarding this universal evidence, but may support the first proposal of allowing the juvenile to present evidence of his actual brain function based on his individual development. While questions regarding the causal link between the individual’s development and his behavior might linger, those questions seem no more significant than questions that arise in the context of the subjective mental state analysis that already occurs for excuse defenses such as insanity or diminished capacity. This presentation of defendant-specific brain science not only overcomes many of the concerns articulated with regard to individualized versus class-wide development, but it provides an even more precisely delineated baseline against which the fact finder can judge the culpability of the defendant’s actions.²⁹⁴ In this, courts would not necessarily need to alter state of mind terminology; rather, as suggested here, they may simply need to alter the perspective through which that terminology is interpreted in order to account for differences between juvenile and adult thought processes.

In each of these suggestions, I am not asserting either that adolescent offenders are categorically incapable of achieving any particular mens rea or should be rendered blameless by their immaturity. Quite the contrary—I am arguing that, like all offenders, adolescents should be held accountable for the mens rea they actually achieved. Or perhaps more accurately, they should be held accountable for the mens rea that the state can prove they achieved through the fact finding process. In this regard, the accuracy of the fact finder’s calibration is critical.

Larger questions regarding how this evidence should be presented, what burdens for proof or persuasion should attach to it, and how defenses would be modified by it, admittedly linger. This Article cannot hope to address them all, at least not if it hopes to maintain any sort of fidelity to word count limitations. But it does aim to open a conversation that scholars, practitioners, and courts seem to have discouraged to date: that the current state of neuroscience on juvenile brain development renders the application of an adultreferenced standard inappropriate. Instead juvenile offenders’ actions must be judged through the lens of their age-calibrated thought processes and cognitive abilities. This Article starts that conversation.

CONCLUSION

The neuroscientific advances described have a great deal to say about how the criminal justice system should treat juvenile offenders. The Supreme Court’s embrace of this science in its Eighth Amendment jurisprudence is a very important step forward. In Miller v. Alabama, Graham v. Florida, and Roper v. Simmons, the Court has relied on evidence of juvenile brain development to conclude that life without the possibility of parole and death sentences violate the Eighth Amendment’s prohibition against cruel and unusual punishment. Likewise in Atkins v. Virginia, the Court relied on neuroscience to hold that the imposition of the death penalty on mentally retarded defendants violated the Eighth Amendment. These cases confirm the Court’s willingness to consider neuroscience when assessing the culpability of particular classes of defendants in determining appropriate and proportional punishment.

Despite this willingness, advocates have achieved little success in utilizing neuroscience outside the context of punishment mitigation. In the face of this judicial reluctance and the admitted limitations of the science itself, scholars have counseled towards curtailment and caution—suggesting a limited role for science in juvenile advocacy. But this conservative approach undermines the value of the science and is logically inconsistent with criminal law’s reliance on the defendant’s mental state as a measure of guilt and blameworthiness.

The continued allegiance to adult-calibrated mens rea standards in the face of scientific confirmation that adolescents utilize different cognitive processes than adults perverts mens rea’s essential purpose. The fact finder’s subjective determination of the defendant’s state of mind requires a careful calculation of what the defendant thought as he acted. The continued reliance on a one-size-fits-all categorization of mens rea and its corresponding rejection of scientific evidence assumes an adult-centric uniformity. The use of this adult standard of mens rea in assessing the guilt of adolescent offenders flies in the face of the most fundamental conclusion currently available from the study of adolescent development—that the thought processes and cognitive abilities of adults and teens are profoundly and qualitatively different. A just system of determining criminal culpability must account for these differences in assessing an adolescent’s mens rea.

Summary

This article argues for a recalibration of the mens rea standard when applied to juvenile offenders, advocating for an approach that considers the distinct cognitive processes of adolescents. Current legal frameworks, the article contends, are inconsistent with scientific findings on adolescent brain development and undermine the purpose of mens rea in assessing juvenile culpability.

I. MENS REA’S ROLE IN CRIMINAL LAW

Mens rea, the mental element in criminal law, differentiates degrees of culpability, placing actions on a continuum of fault. The determination of a defendant's mental state often involves inferring intent from actions, a process influenced by the fact-finder's own experiences and understanding, despite legal guidance in defining mental states. This existing approach, the article argues, assumes a uniform, adult-referential baseline for cognitive processes, neglecting the significant differences between adolescent and adult cognitive functioning.

II. THE COURT, THE LAW, AND THE KIDS

The Supreme Court's jurisprudence on youth, particularly in Roper v. Simmons, Graham v. Florida, Miller v. Alabama, and J.D.B. v. North Carolina, acknowledges that adolescents' decision-making processes differ from adults'. These rulings, while focused on sentencing, recognize the role of mental state in assessing culpability and highlight the need for age-appropriate legal standards. The article asserts that this recognition of difference should extend to substantive criminal law's mens rea standards.

III. THE SCIENCE OF ADOLESCENCE AND WHAT IT MEANS FOR CULPABILITY

Scientific evidence demonstrates significant differences in adolescent cognitive processes compared to adults. Adolescents exhibit deficiencies in executive functions, including risk assessment, impulse control, and long-term consequence consideration. This is not a defect but a characteristic of normal adolescent development, influencing their understanding of choices and their actions. While research offers insights, limitations remain regarding individual variability and the precise impact of neurological factors on behavior.

IV. THE NEXUS OF NEUROSCIENCE AND MENS REA

Applying adult-based mens rea standards to adolescents distorts the assessment of culpability. The article proposes that courts should consider adolescents' distinct cognitive processes when interpreting mens rea, arguing against a solely adult-referential standard. The authors suggest allowing the presentation of both universal neuroscientific evidence on adolescent development and individualized evidence to provide a more accurate assessment of an adolescent's mental state at the time of the offense. This approach seeks to maintain accountability while acknowledging the inherent differences in adolescent cognitive functioning.

Summary

Mens rea, the mental element in criminal law, differentiates culpability. Current mens rea standards, however, assume uniform adult cognitive processes, ignoring scientific evidence showing adolescent cognitive differences. This article argues for recalibrating mens rea standards for juveniles to reflect adolescent brain development, aligning with Supreme Court precedent acknowledging differences in juvenile decision-making.

I. Mens Rea’s Role in Criminal Law

Criminal law links culpability and blameworthiness. Mens rea distinguishes blameworthy acts from culpable ones deserving punishment. It establishes a culpability continuum, ranging from accidental to premeditated conduct. While not always precise, mens rea sets the threshold for punishment, balancing deserved punishment with protection against disproportionate sentencing. The concept assumes an understanding of social norms, the ability to conceptualize actions within those norms, and the capacity to understand consequences. It necessitates an understanding of cause-and-effect relationships and the ability to make independent choices, aligning actions with community values.

A. Brief History of Mental States

Historically, culpability was broadly defined. As legal systems advanced, distinctions arose between degrees of culpability: negligence, recklessness, intentionality, and premeditation. Defenses like insanity and diminished capacity also consider the offender's mental state. The common law's imprecise definitions led to the Model Penal Code (MPC).

B. The Rise of the MPC and Defined Mens Rea

The MPC categorizes mens rea (purposely, knowingly, recklessly, negligently), aiming for clarity and consistency. It links mental states to culpability levels and punishments. The MPC distinguishes subjective (defendant's actual thoughts) and objective (reasonable person standard) mental states, influencing punishment severity.

C. Problems with Mens Rea

The MPC's categorization is problematic. It assumes mental states are easily discerned, relies heavily on inference, and the “beyond a reasonable doubt” standard introduces juror subjectivity. Jurors interpret evidence through their own experiences, potentially leading to inaccurate assessments of the defendant's mental state.

II. The Court, the Law, and the Kids

Supreme Court jurisprudence increasingly recognizes the legal significance of youth.

A. Youth and the Eighth Amendment

The Court's Eighth Amendment jurisprudence considers cognitive development when determining sentencing proportionality. Cases like Roper v. Simmons, Graham v. Florida, and Miller v. Alabama demonstrate a shift towards recognizing that juveniles' underdeveloped brains impact culpability, leading to restrictions on certain punishments. These decisions build upon earlier cases acknowledging juveniles' immaturity and vulnerability. Atkins v. Virginia further reinforces this trend by considering cognitive deficiencies in relation to culpability.

B. The Jurisprudence of Youth

The Court's treatment of juveniles reflects a broader legal recognition of their distinct status. Numerous legal restrictions and protections acknowledge the differences between children and adults. J.D.B. v. North Carolina extends this by applying an age-appropriate standard of reasonableness in Miranda custody analysis.

III. The Science of Adolescence and What It Means for Culpability

Scientific evidence supports the legal distinction between adult and adolescent cognitive processes.

A. The Juvenile Justice System

The creation of separate juvenile justice systems reflects an early recognition of differences between adult and juvenile offenders. However, recent trends show increasing punitive measures, blurring the line between juvenile and adult systems.

B. The Scientific Literature

Neuroscientific studies reveal significant differences in adolescent brain development impacting executive functions like decision-making, risk assessment, and impulse control. These differences aren't defects but normative developmental characteristics. While the timing and trajectory of development vary, the core characteristics are consistent across adolescents. This research highlights the transient nature of adolescent risky behavior. Studies have shown that the adolescent brain is still developing, particularly the prefrontal cortex. Myelination and pruning of gray matter impact brain efficiency and decision-making abilities, which continue to mature into early adulthood. Adolescents exhibit heightened sensitivity to social cues and rewards.

1. What We Know

Adolescents are less competent decision-makers than adults. They have deficiencies in autonomous choice, self-management, risk perception, and calculating future consequences. These are developmental hallmarks, not defects.

2. What We Don’t Know

Neuroscience offers limited insight into individual behavior. While studies reveal trends, individual variations exist, and external factors significantly influence behavior. Confirmation bias is also a concern in court applications.

IV. The Nexus of Neuroscience and Mens Rea

Applying adult mens rea standards to juveniles distorts the assessment of culpability. It ignores adolescents' unique cognitive processes and undermines mens rea's purpose.

The continued use of adult-based mens rea standards for juveniles is inappropriate given the scientific evidence of cognitive differences. The courts' reluctance to consider neuroscience in mens rea assessments is illogical and inconsistent with their own rulings regarding juvenile culpability in sentencing. While the court might assert that such an adjustment needs to come from legislation, such an assumption ignores the fact that mens rea is already established as a crucial element of fact.

To accurately assess mens rea, courts should consider two approaches: presenting evidence of the individual's cognitive function or presenting universal neuroscientific evidence demonstrating typical adolescent traits. This would provide fact-finders with a relevant baseline for interpretation, minimizing confirmation bias and ensuring a fairer assessment of culpability. While there are limitations and unanswered questions, the need to account for adolescent brain development in mens rea is essential. The goal is not to excuse juvenile offenders but to achieve a more accurate assessment of their actual culpability.

Conclusion

Neuroscience significantly impacts how the justice system treats juvenile offenders. While the Supreme Court has embraced neuroscience in Eighth Amendment jurisprudence, its application remains limited. A more comprehensive approach is needed to fully integrate neuroscience into mens rea assessments, acknowledging the significant cognitive differences between adolescents and adults. Using an adult-centric mens rea standard for juvenile offenders perverts mens rea’s purpose. A just system must account for these differences.

Summary

Mens rea, the mental state element in criminal law, distinguishes degrees of culpability. Current legal standards assume a uniform, adult-based understanding of thought processes, but this approach is challenged by scientific evidence showing significant differences in adolescent cognitive development. This article argues for recalibrating mens rea standards for juveniles to align with current understandings of adolescent brain development. This argument aligns with Supreme Court precedent recognizing differences in juvenile decision-making, as seen in cases involving sentencing and Miranda rights. The article explores the role of mens rea in criminal law, the Supreme Court's jurisprudence on youth, scientific findings on adolescent brain development, and proposes a framework for incorporating these findings into mens rea assessments for juveniles.

I. MENS REA’S ROLE IN CRIMINAL LAW

Criminal law connects culpability and blameworthiness. Mens rea, a crucial element, differentiates blameworthy from culpable acts deserving punishment. It distinguishes accidental from intentional actions. The concept assumes a baseline understanding of social norms, the ability to conceptualize actions within those norms, and membership in social networks that shape understanding of social norms. It also assumes an understanding of consequences and an ability to make independent choices based on this understanding. Historically, defining mental states has been challenging, with early distinctions focusing on accidental vs. non-accidental acts. Common law developed categories like negligence, recklessness, intentionality, and premeditation. Defenses like insanity and diminished capacity also consider the defendant's mental state. The Model Penal Code (MPC) attempted to standardize mens rea definitions, categorizing mental states (purposely, knowingly, recklessly, negligently), but applying these categories in practice presents challenges. Proof of mens rea often relies on inference, and the beyond-a-reasonable-doubt standard introduces juror subjectivity into the assessment of the defendant's state of mind.

II. THE COURT, THE LAW, AND THE KIDS

Supreme Court decisions increasingly acknowledge the developmental differences between adolescents and adults. The Court uses scientific evidence to show juveniles lack the same culpability as adults, particularly in cases related to sentencing. Starting with Eddings v. Oklahoma, the Court highlighted the immaturity and vulnerability of juveniles. Roper v. Simmons, Graham v. Florida, and Miller v. Alabama established that certain punishments (death penalty, life without parole) are disproportionate for juveniles due to their underdeveloped brains and decision-making processes. J.D.B. v. North Carolina extended this principle to Miranda custody analysis, requiring an age-appropriate standard of reasonableness. This jurisprudence of youth reflects broader legal recognition of minors' distinct status, with various legal restrictions and protections based on age.

III. THE SCIENCE OF ADOLESCENCE AND WHAT IT MEANS FOR CULPABILITY

Scientific research supports the legal distinction between adolescent and adult decision-making. Studies reveal adolescents have less developed executive functions, impacting their risk assessment, self-control, and understanding of long-term consequences. This isn't a defect but a normal developmental stage. The juvenile justice system, initially focused on rehabilitation, has shifted towards punitive measures. Neuroscience provides biological explanations for observed adolescent behaviors. Brain imaging shows the prefrontal cortex, crucial for decision-making, matures later in development. Myelination and gray matter pruning during adolescence impact brain efficiency. While adolescence involves risky behaviors, these are part of normal development. Scientific limitations include the lack of individual-specific insights and the complexity of isolating biological factors from other influences on behavior.

IV. THE NEXUS OF NEUROSCIENCE AND MENS REA

Applying adult mens rea standards to adolescents distorts the assessment of culpability. The article argues for incorporating adolescent neuroscience into mens rea evaluations. The court in State v. Heinemann exemplifies the judicial reluctance to modify mens rea standards based on adolescent brain development. J.D.B. however, demonstrates that age is a relevant factor in determining reasonableness. To accurately assess mens rea, the juvenile's actual cognitive processes must be considered. The article proposes two approaches: allowing juveniles to present evidence of their individual cognitive functions or presenting universal neuroscientific evidence showing typical adolescent traits. Both approaches aim to provide a more accurate assessment of mens rea, recognizing the unique cognitive capabilities of adolescents without absolving them of responsibility. The article concludes by emphasizing the need for a justice system that recognizes and accommodates the developmental differences between adolescents and adults in assessing culpability.

Summary

This article discusses how the legal concept of mens rea (a person's mental state) should be applied to young people accused of crimes. It argues that current laws assume everyone thinks like adults, which isn't true. The article suggests that because teenagers' brains are still developing, their understanding of right and wrong is different from adults. This means judges and juries need to consider this difference when deciding if a teen is guilty.

I. MENS REA’S ROLE IN CRIMINAL LAW

Criminal law decides if someone did something wrong and how much they should be punished. Mens rea helps figure out how much blame someone deserves. It shows the difference between an accident and a deliberate act. Imagine a dog getting kicked versus tripping over a dog – one is intentional, the other is not. Mens rea is like that, it shows the difference between a mistake and a crime. Even if someone causes harm, without mens rea, it’s usually not a crime.

The law assumes people know basic rules of right and wrong. It also assumes they understand the results of their actions and can make choices. If someone breaks the law, it shows they chose to ignore the rules.

A. Brief History of Mental States

For a long time, the law simply separated accidents from deliberate acts. Then, it added levels of blame based on how much someone knew about what they were doing. For example, being careless is different from knowing there's a risk and doing it anyway. Intentionally doing something is even worse, and planning a crime beforehand makes it the worst.

The law also has defenses where a person's mental state matters. If someone is really mentally ill, they may not be blamed. If they were really angry or upset, that might make the punishment lighter. Even self-defense depends on what someone thought was happening.

B. The Rise of the MPC and Defined Mens Rea

The Model Penal Code (MPC) tried to make things clearer. It created four levels of mens rea: purposely, knowingly, recklessly, and negligently. It helped define how much blame someone deserves based on what they knew and intended. It also tried to separate what someone actually thought from what a normal person would think.

C. Problems with Mens Rea

The MPC’s system is tricky. It’s hard to know what someone is really thinking. The law often relies on clues to guess their mental state. Juries also use their own experiences to decide if someone is guilty, so their opinions can be different.

II. THE COURT, THE LAW, AND THE KIDS

The Supreme Court has made decisions that recognize young people are different from adults. It's harder to blame a teenager the same way as a grown-up because teens’ brains aren't fully developed. The Court has said that this means teens can't always get the same punishments as adults.

A. Youth and the Eighth Amendment

The Court has looked at brain science to understand how teens think and make decisions. Studies show teens are more impulsive and less able to think about the long-term consequences of their actions. This is why the Court has decided it’s wrong to give teenagers the death penalty or life in prison without parole for some crimes.

B. The Jurisprudence of Youth

Many laws already treat kids differently from adults. Teens can't vote, join the military, or buy alcohol. These laws show that the law already acknowledges teens are not the same as adults. The Court recently used brain science to explain why teens should be treated differently when the police question them.

III. THE SCIENCE OF ADOLESCENCE AND WHAT IT MEANS FOR CULPABILITY

Recent brain studies confirm that teens' brains are still developing, especially the part that helps with decision-making. This makes them more likely to take risks and have trouble thinking about long-term results. This isn't a problem with their brains; it's a normal part of growing up.

A. The Juvenile Justice System

The juvenile justice system was created to help young people, not just punish them. However, it has become more like the adult system over time. Now, the article discusses the use of brain science to better assess the culpability of teens in the judicial system.

B. The Scientific Literature

1. What We Know

Studies show teens are less good at making decisions than adults. Their brains are still developing, which affects their ability to think about risks and consequences. They are more easily influenced by friends and are more focused on immediate rewards.

2. What We Don’t Know (or the Limits of Science)

Science can't tell us exactly how every teen will behave. Brain development varies, and other things affect behavior. Also, studies often happen in controlled settings and sometimes that's different than real life.

IV. THE NEXUS OF NEUROSCIENCE AND MENS REA

Using adult standards of mens rea for teens is unfair because it ignores how their brains work differently. The courts should consider a teen’s brain development when deciding their guilt. This does not mean teens should not be held accountable, but rather held accountable based on what they actually understood, not based on what an adult would have understood.

CONCLUSION

Brain science shows teens think differently than adults. This should affect how the law handles their crimes. The law needs to acknowledge this difference when deciding if a teen is guilty and how much they should be punished. Using adult standards is not fair and does not accurately determine culpability.