In a 5–4 decision, the Supreme Court today held that the Eighth Amendment prohibits sentencing schemes that result in mandatory life without the possibility of parole (LWOP) sentences for juvenile killers. Writing for the majority, Justice Elena Kagan noted that “youth matters in determining the appropriateness of a lifetime of incarceration.” States may still impose LWOP sentences for teenagers convicted of aggravated murder, as long as the sentencing scheme takes into account the offender’s age and diminished blameworthiness.

The Court considered two companion cases, Miller v. Alabama and Jackson v. Hobbs. Miller was 14 years old when he and a friend robbed an intoxicated neighbor and then beat him with a baseball bat, set his trailer on fire, and left him to die.

Jackson was also 14 when he and two other teenagers attempted to rob a video store in Blytheville, Arkansas. One of Jackson’s accomplices threatened a female store clerk with a sawed-off shotgun. When the clerk refused to turn over the money, Jackson told her, “We ain’t playin.’” When she threatened to call the police, Jackson’s accomplice shot her in the face, killing her.

In both cases, the defendants were found guilty of capital murder and given LWOP sentences. In Arkansas, a defendant convicted of capital murder will be sentenced either to death or LWOP, so because of his age, Jackson’s LWOP sentence was essentially mandatory. In Alabama, capital murder carries a mandatory minimum sentence of LWOP. Thus, the Supreme Court treated both sentences as mandatory.

Thirty-nine states and the federal government provide for the possibility of LWOP for teenagers 14 years or older who commit aggravated murder—and 28 states and the federal government make LWOP the mandatory sentence for certain aggravated crimes. This is not surprising, given the alarming rate of murders that are committed by teenagers in this country. The United States leads the Western world in juvenile crime rates; in 2002, according to the World Health Organization, the United States ranked third overall and 14th per capita in murders committed by youth.

The Supreme Court had previously determined in Roper v. Simmons (2005) that the death penalty was unconstitutional for teenage murderers under the Eighth Amendment. And in Graham v. Florida (2010), the Court held that LWOP sentences for teenagers who commit violent crimes other than murder were also unconstitutional.

The Eighth Amendment was originally intended to bar “inhuman and barbarous” punishments, such as torture and other inhumane methods of inflicting punishment; however, it did not address the duration of punishment, whether for a term of years or for life. However, as Justice Clarence Thomas’s dissent points out, the Court has long departed from this original meaning.

The defendants in these cases argued that imposing LWOP sentences on teenagers amounts to cruel and unusual punishment, since teenagers are inherently less morally culpable (or blameworthy) than adult offenders. Relying heavily on studies by social scientists, sentencing practices in other countries, and on other international legal instruments, the defendants argued that imposing LWOP on a teenage offender under any circumstances would violate the Eighth Amendment under the Supreme Court’s amorphous and pliable standard of evaluating whether a particular sentencing practice violates “the evolving standards of decency that mark the progress of a maturing society” (Trop v. Dulles, 1958).

Constitutional prohibitions should not be based on social science. Social science does not tell us anything that isn’t already well known to any parent: Teenagers do not always exercise the same judgment as adults and may be incapable of doing so, and they do not always think sufficiently deeply about the consequences of their actions. While social science may be relevant to these issues, such judgments should be left to the elected representatives who are accountable to the people who live in the communities where such crimes are committed—not judges who must only interpret the law.

The vast majority of teenagers are tried in juvenile courts; every state has them. These systems exist because most people believe that most teenage criminals can be rehabilitated or, at the very least, ought to be given that opportunity. However, the citizens of most states also believe that there is a small percentage of teenagers who commit particularly heinous crimes and are not capable of rehabilitation. This small percentage of the worst teenage offenders should be tried in the adult court system and deserve the same harsh treatment that adults who commit the same crimes receive. There is nothing inherently wrong with allowing a state to show its intolerance for the taking of a human life by imposing the harshest of sentences (short of the death penalty, which the Court has found unconstitutional for teenagers) on the person who does it, even if that person was a teenager at the time he committed the crime. The Court’s decision today does not change this—it only requires individualized sentencing for juveniles.