A 71-year-old Louisiana inmate whose case led to a landmark U.S. Supreme Court decision on juvenile-offender sentences was denied parole Monday, more than a half-century after he killed a sheriff's deputy at age 17.

A three-member panel from the state parole board voted 2 to 1 to keep Henry Montgomery imprisoned. The hearing was his first chance at freedom since his conviction decades ago and a vote to free him would have had to be unanimous. Montgomery now must wait another two years before he can request another parole hearing.

The Supreme Court's January 2016 decision in Montgomery's case opened the door for roughly 2,000 other juvenile offenders to argue for their release after receiving mandatory life-without-parole sentences.

Montgomery has served 54 years in prison for shooting East Baton Rouge Parish sheriff's deputy Charles Hurt in 1963, less than two weeks after Montgomery's 17th birthday. Last June, a state judge who resentenced Montgomery to life with the possibility of parole called him a "model prisoner" who seemed to be rehabilitated.

Montgomery's lawyers said he has sought to be a positive role model for other prisoners, serving as a coach and trainer for a boxing team he helped form at Louisiana State Penitentiary at Angola.

But the two parole board members who voted against Montgomery questioned why he hadn't accessed more prison programs and services that could have benefited him. One of the panelists, Kenneth Loftin, also said he was disappointed in some of Montgomery's statements during the hearing but didn't elaborate.

James Kuhn, the other board member who voted against Montgomery, noted that the Louisiana Sheriffs' Association submitted a statement opposing his release.

"One of the things that society demands, and police officers certainly demand, is that everyone abide by the rule of law. One of the rules of law is you don't kill somebody, and when you do there's consequences," Kuhn said.