Summary of Argument

The adolescent's mind works differently from ours. Parents know it. This Court has said it. Legislatures have presumed it for decades or more. And now, new scientific evidence sheds light on the differences.

Scientists have documented the differences along several dimensions. Adolescents as a group, even at the age of 16 or 17, are more impulsive than adults. They underestimate risks and overvalue short-term benefits. They are more susceptible to stress, more emotionally volatile, and less capable of controlling their emotions than adults.

In short, the average adolescent cannot be expected to act with the same control or foresight as a mature adult.

Behavioral scientists have observed these differences for some time. Only recently, however, have studies yielded evidence of concrete differences that are anatomically based. Cutting-edge brain imaging technology reveals that regions of the adolescent brain do not reach a fully mature state until after the age of 18. These regions are precisely those associated withimpulsecontrol,regulationofemotions, risk assessment, and moral reasoning. Critical developmental changes in these regions occur only after late adolescence.

Science cannot, of course, gauge moral culpability. Scientists can, however, shed light on certain measurable attributes that the law has long treated as highly relevant to culpability. This Court has concluded that both adolescents who are under age 16 and mentally retarded persons exhibit characteristics - “disabilities in areas of reasoning, judgment, and control of their impulses,” Atkins v. Virginia, 536 U.S. 304, 306 (2002) - that categorically disqualify them from the death penalty. Offenders at age 16 and 17 exhibit those characteristics as well.

Summary of Argument

The adolescent brain functions differently from that of an adult. This is recognized by parents, the courts, and legislators. Recent scientific advancements offer greater understanding of these differences.

Research has identified notable distinctions in adolescent brain development. Even at ages 16 or 17, adolescents, as a group, exhibit higher levels of impulsivity compared to adults. They tend to underestimate risks and prioritize immediate gratification over long-term consequences. Adolescents are also more susceptible to stress, experience greater emotional volatility, and struggle with emotional regulation compared to adults.

Consequently, the typical adolescent cannot be expected to exercise the same level of self-control or foresight as a mature adult.

Behavioral scientists have observed these developmental differences for some time. However, recent studies have provided evidence of concrete, anatomical distinctions. Advanced brain imaging techniques demonstrate that certain regions of the adolescent brain do not fully mature until after the age of 18. These regions are directly linked to impulse control, emotional regulation, risk assessment, and moral reasoning. Significant developmental changes within these regions occur only after late adolescence.

While science cannot definitively determine moral culpability, it can illuminate measurable attributes that have long been deemed relevant to legal accountability. The Court has acknowledged that both individuals under 16 years of age and those with mental retardation exhibit characteristics – "disabilities in areas of reasoning, judgment, and control of their impulses," *Atkins v. Virginia, *536 U.S. 304, 306 (2002) – that categorically disqualify them from the death penalty. Similarly, offenders aged 16 and 17 exhibit these same characteristics.

Summary of Argument

The human brain develops throughout a person's life, and this development is particularly pronounced during adolescence. Scientific evidence now confirms what parents and legal systems have long recognized: the adolescent brain functions differently from an adult brain.

Research in the field of neuroscience has revealed significant differences between the brains of adolescents and adults. Studies using advanced brain imaging techniques have shown that certain brain regions, particularly those associated with impulse control, emotional regulation, risk assessment, and moral reasoning, do not fully mature until after the age of 18. This means that adolescents, even those approaching adulthood, may be more likely to engage in impulsive behaviors, underestimate risks, and struggle to control their emotions.

While science cannot definitively determine moral culpability, it provides valuable insights into biological factors that influence decision-making and behavior. The legal system has long recognized that certain groups, such as individuals under the age of 16 and those with intellectual disabilities, exhibit characteristics that impact their capacity for reasoned judgment and impulse control. These characteristics, which often include impulsivity, poor risk assessment, and emotional volatility, have been deemed significant enough to disqualify these individuals from capital punishment.

The emerging evidence from neuroscience strongly suggests that adolescents aged 16 and 17 also exhibit these same characteristics due to their developing brains. Therefore, the legal system should consider the biological realities of adolescent brain development when evaluating culpability and sentencing.

Summary of Argument

The brains of teenagers are different from the brains of adults. This is something that parents, judges, and lawmakers have recognized for a long time. Now, new scientific discoveries provide more evidence about these differences.

Scientists have shown that teenagers, even at the ages of 16 and 17, are more likely to act impulsively than adults. They don't think about the risks as much, and they focus more on what will benefit them right now, even if it means trouble in the future. They are also more easily affected by stress, have more emotional ups and downs, and have a harder time controlling their feelings.

In other words, the typical teenager isn't expected to have the same level of self-control or foresight as a grown-up.

Experts who study behavior have noticed these differences for a while now. But only recently have scientists been able to find clear evidence of physical differences in the brain. New technology that lets us see inside the brain shows that certain parts of a teenager's brain don't fully develop until they are older than 18. These areas are the ones that control impulses, emotions, risks, and moral thinking. Important changes in these areas of the brain happen even after teenagers finish high school.

Science can't tell us if someone deserves punishment for a crime. But scientists can help us understand certain qualities that the law has always considered important when deciding if someone should be punished. The Supreme Court has already ruled that people under 16 and people with mental disabilities can't be sentenced to death because they have certain characteristics – trouble with thinking, making judgments, and controlling impulses. *Atkins v. Virginia, *536 U.S. 304, 306 (2002). People who are 16 or 17 years old also have these characteristics.

Summary of Argument

Teens think differently than adults. Parents know this, and judges and lawmakers have thought so for a long time. Now, scientists are learning more about how teen brains work.

Scientists say teens are more likely to act without thinking, take risks, and want things now instead of later. They also get stressed easily, get upset more often, and have trouble controlling their feelings. Basically, teens don't have the same self-control or ability to plan ahead like adults.

Scientists have known about these differences for a while, but now they are using special machines to look at teens' brains. These machines show that some parts of a teen's brain aren't fully grown until after they turn 18. These are the parts that help teens control their actions, manage their feelings, think about risks, and make good choices. These parts of the brain keep changing until teens are almost adults.

Science can't tell if someone is guilty or not, but it can help us understand why teens might do things differently. Judges have said that kids younger than 16 and people with mental disabilities can't be given the death penalty because they have problems with thinking, making good decisions, and controlling their actions. Teens who are 16 or 17 years old also have these kinds of problems.