SALT LAKE CITY — Utah’s two prisoners serving life without parole for slayings they carried out as 17-year-olds both tried and failed to appeal their sentences, keeping them in prison despite two key rulings from the U.S. Supreme Court on juvenile lifers.

Robert Cameron Houston took his appeal alleging his sentence was “cruel and unusual punishment” all the way to the U.S. Supreme Court, but the justices declined to take the case. That came after the Utah Supreme Court upheld the sentence, too.

Authorities say Cameron raped and killed a 22-year-old youth counselor who gave him a ride from a group home for troubled teens to another facility during a snowstorm in 2006.

Michael Teter a University of Utah law professor, made the request on Cameron’s case to the U.S. Supreme Court in 2015. Teter said Cameron’s difficult childhood, with physical and sexual abuse, wasn’t adequately presented during trial by his attorney, preventing the jury from being able to consider it when Cameron was found guilty in 2007.

“Cameron Houston will never have even the opportunity to demonstrate to a parole board that he has changed,” Teter wrote.

Morris Mullins killed a 78-year-old woman in 2001 in a small central Utah town, police said. He was sentenced to life without parole as part of a plea deal. Last year, he requested a resentencing based on the argument that his attorney didn’t properly explain the deal to him. That was denied.

Five years ago, the U.S. Supreme Court barred states from imposing mandatory life-without-parole sentences on anyone under 18 convicted of murder. Last year, the court made its ruling retroactive, saying the more than 2,000 offenders already serving such sentences must be given the chance “to show their crime did not reflect irreparable corruption” and, if it did not, they should have some hope for freedom.

The court found the harshest punishments levied against adult criminal offenders are unconstitutionally cruel and unusual when imposed on juveniles, because of their lack of development and potential for change.

And yet for those who have received these now-illegal life terms, the ruling’s promise of resentencing and a chance at eventual release has so far been halting, inconsistent and often elusive, a 50-state examination by The Associated Press found.

Utah law never required life in prison without parole for any juvenile, making it discretionary instead. But last year, the state joined others in banning life without parole sentences for juveniles in any new cases.