The legal proceedings in State of Arizona v. Gregory Nidez Valencia Jr. (2016) centered on the constitutionality of a mandatory life sentence without the possibility of parole imposed on a juvenile offender, Gregory Valencia Jr. Valencia argued that the sentence constituted cruel and unusual punishment, violating the Eighth Amendment to the U.S. Constitution. This case arose following the Supreme Court's ruling in Miller v. Alabama (2012), which deemed mandatory life sentences without parole for juvenile offenders unconstitutional due to the failure to consider individual potential for rehabilitation. While Arizona courts had previously upheld Valencia's sentence, the Arizona Supreme Court, in light of the precedent established by Miller v. Alabama, overturned its prior rulings, concluding that the sentence was indeed unconstitutional.

The 2016 case of State of Arizona v. Gregory Nidez Valencia Jr. centered on the constitutionality of a mandatory life sentence imposed on Gregory Valencia Jr., a juvenile at the time of his offense. Valencia's legal team argued that the sentence, which offered no possibility of parole, constituted cruel and unusual punishment, a violation of the Eighth Amendment. This argument arose in the wake of the Supreme Court's pivotal ruling in Miller v. Alabama (2012), which deemed mandatory life sentences without parole for juveniles unconstitutional, as such sentences failed to consider a juvenile's capacity for rehabilitation. Despite previous rulings by Arizona courts upholding Valencia's sentence, the Arizona Supreme Court, taking into account the precedent set by Miller v. Alabama, ultimately overturned the sentence, declaring it a violation of the Constitution.

In 2016, a case in Arizona called State of Arizona v. Gregory Nidez Valencia Jr. brought up an important question: can someone who commits a crime as a teenager be sentenced to life in prison without the chance of ever getting out? Gregory Valencia Jr. argued that this kind of sentence was a violation of the Eighth Amendment, which protects against cruel and unusual punishment.

His argument came after a big decision by the Supreme Court in 2012 called Miller v. Alabama. In that case, the highest court decided it was unconstitutional to give a juvenile offender a life sentence without parole (meaning they never get released) without thinking about their potential to change for the better. Even though lower courts in Arizona had initially agreed with Valencia's original sentence, the Arizona Supreme Court ultimately decided that, because of the Miller v. Alabama decision, his life sentence without parole was unfair and went against the Constitution.

In 2016, a young man named Gregory Nidez Valencia Jr. went to court in Arizona to argue against his life sentence. Gregory, who was a teenager when he went to prison, believed his punishment was unfair and went against the Eighth Amendment. This amendment, which is part of the United States Constitution, forbids "cruel and unusual punishment." Gregory argued that being sent to prison for life without the chance of parole, even though he was young when he committed his crime, was cruel.

Gregory's case became important because, in 2012, the Supreme Court of the United States made a big decision in a case called Miller v. Alabama. The Court said that it was unconstitutional to automatically give minors a life sentence without carefully thinking about their chances of changing for the better. Before this decision, courts in Arizona had said Gregory's sentence was okay. But, because of the Miller v. Alabama ruling, the Arizona Supreme Court finally agreed that Gregory's life sentence was unconstitutional.