HELENA — Attorneys for a Montana State Prison inmate serving a 100-year sentence without the possibility of parole in a 1979 homicide are arguing he should be resentenced under rulings from the nation’s top court that found juveniles can’t be held to the same standards of moral culpability as adults.

Peter Camiel on Wednesday asked the Montana Supreme Court to find that a 2012 U.S. Supreme Court ruling requiring judges to consider mitigating factors before sentencing a juvenile to life in prison without the possibility of parole applies in Barry Beach’s case.

Research in brain development found juveniles lack the same capacity as adults to appreciate the consequences of their actions or control their impulses, and they have a greater potential for reform, the U.S. Supreme Court rulings say.

Camiel asked that Beach be resentenced for the death of Kimberly Nees of Poplar, arguing he is serving the equivalent of a life sentence, which the country’s highest court has found amounts to unconstitutional cruel and unusual punishment for juveniles.

The crime occurred when Beach was 17, although he has maintained his innocence.

Wednesday’s main argument was whether the U.S. Supreme Court ruling was retroactive and would apply to Beach.

Assistant Attorney General Tammy Plubell argued a presentence report was thorough and addressed Beach’s family circumstances, employment and prior record and that he was given a legal sentence.

Camiel argued Beach’s 1984 sentence did not take into consideration that juveniles are different from adults and should be given a meaningful opportunity for release. He said Beach would have to live past his life expectancy before he would be released from prison under his current sentence.

Plubell argued Beach had the opportunity on appeal to argue the fairness of his sentence, and it was upheld. But justices noted that happened without the benefit of current science on brain development.

The state Supreme Court took the arguments under advisement.

Beach has argued for decades that he did not kill Nees and that the confession used to convict him was coerced. With the help of Centurion Ministries, he has tried to get his conviction overturned, sought a new trial, requested that he be given parole eligibility and asked that his sentence be commuted to time served.

On Wednesday, Camiel said the current effort recognizes that Beach’s conviction is final and if his case is remanded for resentencing he would be treated as being guilty.

Plubell said Nees’ mother has suffered in silence for decades as Beach’s appeals have continued, and it’s time for the case to be settled.