The Supreme Court ruled on Monday that states may not impose mandatory life sentences without parole on juveniles, even if they have been convicted of taking part in a murder.
The justices ruled in a 5-to-4 decision that such sentencing for those under 18 violated the Eighth Amendment's ban on cruel and unusual punishment. The ruling left open the possibility of judges' sentencing juveniles to life imprisonment without parole in individual circumstances but said state laws could not automatically impose such sentences.
"Mandatory life without parole for a juvenile precludes consideration of his chronological age and its hallmark features -- among them, immaturity, impetuosity, and failure to appreciate risks and consequences," Justice Elena Kagan wrote for the majority. "It prevents taking into account the family and home environment that surrounds him -- and from which he cannot usually extricate himself -- no matter how brutal or dysfunctional."
Justice Kagan's opinion argued that the two cases at issue, involving 14-year-old boys who had taken part in murders in Arkansas and Alabama, were an extension of the court's recent rulings on the young, which asserted that they still had unformed emotional and moral structures and that treating them as adults violated "the evolving standards of decency that mark the progress of a maturing society."
One such recent decision declared it unconstitutional to sentence juveniles to life in prison who were involved in crimes that did not include killing, and others barred the death penalty from being imposed on teenagers and the mentally retarded.
Justice Kagan was joined by Justices Anthony M. Kennedy, Ruth Bader Ginsburg, Stephen G. Breyer and Sonia Sotomayor.
Nearly 2,500 juvenile offenders are serving life sentences without parole in the United States. Human rights groups say there are almost no other countries that put teenagers in prison and keep them there to die without the possibility of parole.
That number was at the core of an angry dissent written by Chief Justice John G. Roberts Jr., who asserted that if something is common it could not, by definition, be "cruel and unusual." He wrote: "Put simply, if a 17-year-old is convicted of deliberately murdering an innocent victim, it is not 'unusual' for the murderer to receive a mandatory sentence of life without parole. That reality should preclude finding that mandatory life imprisonment for juvenile killers violated the Eighth Amendment."
He added, in a dissent joined by Justice Antonin Scalia, Clarence Thomas and Samuel A. Alito Jr., that the court's notion of evolving decency was flawed and was based not on history but on the views of the five justices who signed the opinion.
"As judges, we have no basis for deciding that progress toward greater decency can move only in the direction of easing sanctions on the guilty," he said.
Justice Alito, who wrote a separate and angrier dissent accusing the court of usurping legislative authority, took the relatively unusual step on Monday of reading parts of his dissent from the bench.
Monday's ruling involved two cases, Jackson v. Hobbs, No. 10-9647, and Miller v. Alabama, No. 10-9646.
In the first, Kuntrell Jackson of Arkansas was 14 when he and two older youths tried to rob a video store in 1999. One of the other youths shot and killed a store clerk, and it was unclear from the case whether Mr. Jackson was in favor of his doing so.
Arkansas law gives prosecutors discretion to charge 14-year-olds as adults in certain circumstances, and the prosecutor in this case did so. Mr. Jackson was sentenced to life without parole.
In the Alabama case, Evan Miller, also 14 at the time, had been in and out of foster care because his mother suffered from alcoholism and drug addiction and his stepfather abused him. Mr. Miller regularly used drugs and alcohol and had tried to commit suicide four times. One night in 2003, he and another youth beat a 52-year-old neighbor and set fire to his house after the three had smoked marijuana and drunk together. The neighbor died of smoke inhalation. Mr. Miller was also tried as an adult and was given life imprisonment without parole.
This article originally appeared in The New York Times.