— A convicted killer imprisoned at the Louisiana State Penitentiary at Angola for a murder 51 years ago deserves a new sentencing hearing because of a 2012 ruling by the U.S. Supreme Court that said mandatory life sentences for juveniles are unconstitutional, a lawyer for the convict told the court in a follow-up case Tuesday.

But a lawyer for the state said the 2012 decision shouldn’t require the decades-old sentence to be reconsidered.

The murderer, Henry Montgomery, is now 69. He was 17 when he shot East Baton Rouge Parish sheriff’s Deputy Charles Hurt, who discovered him hiding in the bushes in a field while playing hooky from Scotlandville High School.

Montgomery was convicted and sentenced to death in 1964, then retried in 1969 and convicted again, with the court imposing a mandatory sentence of life without parole.

In the separate 2012 case, the Supreme Court said mandatory life sentences for juvenile offenders violate the ban on cruel and unusual punishments in the Eighth Amendment to the U.S. Constitution. A juvenile murderer still may be sentenced to life without parole, the court said, but not as a mandatory punishment and not without a hearing to consider extenuating circumstances relating to his or her age.

“The question is, is Mr. Montgomery being held constitutionally?” Mark Plaisance, of the East Baton Rouge Parish Public Defenders Office, who represents Montgomery, asked during the session before the Supreme Court.

The Louisiana Legislature changed sentencing laws in 2013 to comply with the 2012 decision. But that didn’t undo the sentences for Montgomery and hundreds of other Louisiana prisoners serving mandatory life sentences imposed when they were juveniles.

Another of those prisoners argued before the Louisiana Supreme Court that the 2012 ruling should apply retroactively, but the state justices disagreed with him in a 2013 decision.

A ruling by the U.S. Supreme Court in the case argued Tuesday is expected by the end of its current session in June.

Most of the 75 minutes of oral argument Tuesday were taken up with a “fantastic discussion,” in the words of one of the lawyers, about whether the issue in the Montgomery case falls under the jurisdiction of the U.S. Supreme Court or lies within the purview of courts in Louisiana. Part of that determination hinges on how significant — the legal term is substantive — the high court’s 2012 decision is seen to be, in its ruling in Miller v. Alabama.

“Miller is a procedural, and not a substantive, rule,” Washington lawyer Kyle Duncan said, arguing on behalf of the Louisiana Attorney General’s Office, which is handling the case for the East Baton Rouge Parish district attorney, in opposition to Montgomery.

The fact that the court in the Miller case did not flatly ban life without parole as a sentence for juveniles supports the argument that the 2012 decision was not substantive, Duncan said: “Leaving the punishment on the table is crucial.”

But in questioning Duncan, Justice Elena Kagan stressed that the court has said in previous cases that changing a minimum allowable sentence is a significant act — and that the Miller case effectively makes that change by opening the door to a lesser penalty than life without parole.

Some states have applied the Miller ruling retroactively to juveniles given mandatory life sentences before 2012, while others have sided with Louisiana and left those sentences in place. Various federal courts also have differed on the issue.

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