(CN) - The Supreme Court ruled Monday that its decision against a mandatory life sentence without parole for juveniles can be applied retroactively.
A divided U.S. Supreme Court ruled in 2012 that the Eighth Amendment forbids mandatory life sentences without the possibility of parole for juvenile murderers.
The decision in Miller v. Alabama rendered such sentences unconstitutional, but the Louisiana Supreme Court refused to apply it retroactively. In 2014, it shot down the petition of Henry Montgomery, an inmate convicted of killing a deputy sheriff in Louisiana.
Attorneys for Montgomery asked the Supreme Court to take the case, noting that the inmate has been incarcerated since 1963, "serving a life sentence for the murder of Charles Hunt that he committed less than two weeks past his seventeenth birthday."
Montgomery's original sentence had been the death penalty, but he was sentenced to life without the possibility of parole on retrial in 1970.
On Monday, the Supreme Court ruled that Miller should be applied retroactively to cases like Montgomery's.
Justice Anthony Kennedy wrote the 50-page ruling, in which the high court ruled 6-3 in favor of Montgomery, who is now 69 years old.
Kennedy noted that the 2012 ruling made life without parole unconstitutional for "a class of defendants because of their status" and created a substantive rule of constitutional law that, like others, is retroactive.
"A state may remedy a Miller violation by extending parole eligibility to juvenile offenders. This would neither impose an onerous burden on the states nor disturb the finality of state convictions," Kennedy wrote. "And it would afford someone like Montgomery, who submits that he has evolved from a troubled, misguided youth to a model member of the prison community, the opportunity to demonstrate the truth of Miller's central intuition - that children who commit even heinous crimes are capable of change."
The Supreme Court reversed the Louisiana Supreme Court's denial of Montgomery's application for review and remanded the case for consideration of parole.
"Henry Montgomery has spent each day of the past 46 years knowing he was condemned to die in prison. Perhaps it can be established that, due to exceptional circumstances, this fate was a just and proportionate punishment for the crime he committed as a 17-year-old boy," Kennedy wrote. "In light of what this Court has said in Roper, Graham, and Miller about how children are constitutionally different from adults in their level of culpability, however, prisoners like Montgomery must be given the opportunity to show their crime did not reflect irreparable corruption; and if it did not, their hope for some years of life outside prison walls must be restored."
Joining Kennedy in the majority opinion were Chief Justice John Roberts and Justices Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan.
Justices Antonin Scalia, Clarence Thomas and Samuel Alito dissented.
Scalia slammed the majority's ruling, calling it a "distortion of Miller" and "a devious way of eliminating life without parole for juvenile offenders."
Constitutional Accountability Center President Elizabeth Wydra said Monday that "the Court followed the Constitution's text and history today and ruled for mercy and justice."
"As the Court reaffirmed today, juveniles are categorically different than adults, and 'children who commit even heinous crimes are capable of change,'" Wydra said in a statement. "This matters when it comes to sentencing, and the Court was right to recognize that."
Read the Top 8
Sign up for the Top 8, a roundup of the day's top stories delivered directly to your inbox Monday through Friday.