The U.S. Supreme Court hears arguments Tuesday in a case that could determine the fate of more than 2,000 convicted juvenile murderers.

In 2012, the high court struck down as unconstitutional state laws that mandated an automatic sentence of life without any possibility of parole in these cases. The question now is whether that decision applies retroactively.

The case before the court began more than a half century ago, when Henry Montgomery, a teenager, was arrested and sentenced to life in prison without parole for the murder of a white deputy sheriff in East Baton Rouge, La. Now 70 years old, Montgomery is asking for a new sentencing hearing.

The case is a procedural spider web, but it will ultimately determine whether some 2,100 people serving life terms for committing murder when they were juveniles have any chance of ever getting out of prison.

In the criminal law, the Supreme Court usually does not make its decisions retroactive, but there are exceptions, and this could be one of them.

The state of Louisiana maintains that the court's decision three years ago did not establish such a major change in the law that it should reach back to apply the ruling to old cases.

The 2012 ruling "doesn't categorically strike down a punishment," says the state's lawyer Kyle Duncan. "It very clearly says that life without parole is still a constitutional punishment for juvenile murderers."

But Mark Plaisance, representing Montgomery, counters that the court's 2012 decision clearly spelled out that juvenile killers could not be automatically sentenced to life in prison, instead suggesting such a draconian punishment should be rare for juveniles.

"When Mr. Montgomery was convicted, the state had only one option: It could only sentence him to mandatory life in prison," Plaisance says. Now, sentencing courts are supposed to consider a variety of sentences well below that in severity in terms of years or the possibility of parole, he says.

Indeed, Louisiana is one of a dozen states that have actually changed laws for juvenile killers to comply with the 2012 Supreme Court ruling. Louisiana now makes parole possible after 35 years in prison. Montgomery would qualify for a parole hearing under the new law, but the state courts have said that law, too, does not apply retroactively.

The state contends that holding new sentencing hearings in these cases would be time-consuming and expensive, and that the results would be inaccurate. Duncan notes that under the Supreme Court's 2012 decision, sentencing judges are supposed to consider the juvenile offender's age, background, the possibility of rehabilitation, and the circumstances of the crime. He says about half of those serving these sentences have been in prison for more than 20 years, and he argues that in many cases the witnesses, prosecutors and defense lawyers — even the judges — may be dead, and school and medical records impossible to find.

To carry out a nuanced consideration of all the circumstances of the crime and the offender, and to do it years — even decades — after the crime took place, he says, would be a mess.

That's a "red herring," says Marsha Levick, one of Montgomery's lawyers. She says that hundreds of these juvenile offenders have already been resentenced in states where the law has been changed or considered retroactive by lower courts.

She argues that these retroactive sentences are in fact far more accurate than prospective sentences.

"Ironically, when you look at these cases 20, 30 or 40 years later," she says, "there's actually much better information about [the defendants'] capacity for rehabilitation, and what's happened to them during their time in prison."

Duncan replies with a question, "Is that relevant?"

"It seems to us really artificial to say, 'Well, he's been in prison and he's shown he can be rehabilitated,' " Duncan says.

Levick, chief counsel for the Juvenile Law Center, disagrees, noting that Montgomery has been a model prisoner for decades. Even without hope of release, she notes, he has served as a coach and trainer for a boxing team he helped establish, and has served as a mentor and counselor for other prisoners.

"I think it's quite remarkable," she says, "looking at someone who spent 50 years in Angola, which was once dubbed ... the bloodiest, the most violent, the most corrupt prison in the United States, that he has retained a measure of dignity, a sense of responsibility, and a sense of his own humanity."

A decision in the case is expected later in the term.

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