By James Vicini
WASHINGTON (Reuters) - The U.S. Supreme Court on Monday ruled unconstitutional mandatory sentences of life in prison without the possibility of parole for people under age 18 when they committed murder in a ruling that could affect nearly 2,500 young prisoners.
By a 5-4 vote, the high court ruled the U.S. Constitution forbids such a mandatory sentencing scheme for juvenile murderers. Conservative Justice Anthony Kennedy joined the liberals while the more conservative members dissented.
The ruling was a major victory for convicted juvenile murderers from Alabama and Arkansas who argued that life imprisonment without the possibility of parole violated the constitutional ban on cruel and unusual punishment.
The ruling could affect nearly 2,500 prisoners serving sentences of life in prison without parole for murder committed under the age of 18. The United States has more than 2.2 million inmates in prisons or jails.
The decision does not mean the prisoners must be released, only that they get the chance for parole.
The ruling is the court's latest at a time when juvenile sentencing trends are reflecting get-tough efforts by states to abolish parole and to prosecute juveniles in the regular criminal justice system for especially heinous crimes.
The Supreme Court in 2010 declared unconstitutional sentences for juveniles of life in prison without parole for crimes other than murder, and in 2005 abolished the death penalty for juveniles.
Opponents of harsh sentences for juvenile offenders have argued they are less responsible for their crimes than adults are due to their emotional immaturity and that they can change and be rehabilitated while in prison.
But law enforcement authorities have argued that sentences of life in prison without parole are in line with the national consensus and are justified for juveniles who commit especially horrific murders.
In the Alabama case, Evan Miller was convicted of murder. A 52-year-old neighbor was smoking marijuana and drinking with Miller and a 16-year-old boy. The two youths robbed the neighbor, beat him with a baseball bat and then set fire to his trailer, causing him to burn to death.
In the Arkansas case, Kuntrell Jackson received a sentence of life in prison in the shooting death of a video store clerk during an attempted robbery with two other teenagers in 1999. Another boy shot the clerk, and Jackson was convicted for his role as an accomplice.
Writing for the court majority, Justice Elena Kagan said the sentencing authority in both cases had no discretion whatsoever to impose a different punishment other than life imprisonment without the possibility of parole.
She said state law mandated that each juvenile die in prison, even if a judge or jury would have thought the offender's age and the nature of the crime would have made a lesser sentence more appropriate.
"By requiring that all children convicted of homicide receive lifetime incarceration without possibility of parole, regardless of their age and age-related characteristics and the nature of their crimes, the mandatory sentencing schemes violate" the constitutional ban on cruel and unusual punishment, she said.
The court's most conservative members, Chief Justice John Roberts and Justices Antonin Scalia, Clarence Thomas and Samuel Alito dissented.
Alito read part of his dissent from the bench, saying the court now holds that Congress and legislatures of all 50 states are barred from identifying any category of murderers under age 18 who must be sentenced to life in prison without parole.
"Even a 17-1/2 year-old who sets off a bomb in a crowded mall or guns down a dozen students and teachers is a 'child' and must be given a chance to persuade a judge to permit his release into society," he said.
Alito said the ruling could lead to young murderers being be released and to kill again.
The Supreme Court cases are Evan Miller v. Alabama, No. 10-9646, and Kuntrell Jackson v. Hobbs, No. 10-9647.
(Editing by Howard Goller and Will Dunham)