The court said it will rule in the case of Louisiana man who was sentenced to life in prison with no chance for parole for shooting his best friend during a botched robbery in 1984 when the convict was 17.
George Toca, the Louisiana inmate, should not "die in prison" without ever having had a chance to show he has been rehabilitated, his lawyer said in her appeal to the high court.
A ruling in his case could affect hundreds across the country.
Two years ago, the justices said in a 5-4 decision that it would be cruel and unusual punishment to impose a mandatory life term with no parole on young murderers.
For the record
2:39 p.m.: An earlier version of this post said the Supreme Court ruled three years ago that a mandatory life term with no parole for young murderers would be cruel and unusual punishment. That ruling was issued two years ago.
Writing in Miller vs. Alabama, Justice
But Kagan and the justices in the majority did not say whether the ruling should be applied retroactively to more than 2,000 state prisoners serving life terms for homicides they committed when they were younger than 18.
Since then, most states, including California, Texas and Illinois, have agreed to give new hearings to these prisoners. This change came about through a state court ruling or a shift in state law.
But other states, including Minnesota, Michigan and Pennsylvania, refused to reopen these old cases. Their state lawyers noted the high court did not say its decision applied retroactively.
On Friday, the court announced it had finally resolved to rule on that issue.
Emily Maw, a New Orleans public defender who appealed Toca's case, raised questions about his guilt as well as the fairness of his sentence. He "was barely 17 years old when his best friend, Eric Batiste, was accidentally shot during a botched armed robbery," she said, calling the shooting "unintended and the result of youthful recklessness."
In the 30 years since then, Toca has "grown into a peaceful adult" who earned a bachelor's degree in prison. He "should be resentenced and have a chance at freedom" some day, she said.
The court will hear arguments in the case in late March and decide the issue by the end of June.