KANSAS CITY (AP) — The U.S. Supreme Court has been clear and consistent: In successive decisions over more than a decade, the justices said the harshest punishments levied against adult criminal offenders are unconstitutionally cruel and unusual when imposed on juveniles. Yet for those who have received now-illegal life terms, the promise of resentencing and a chance at eventual release has so far been halting, inconsistent and sometimes elusive, a 50-state examination by The Associated Press found. Here's a look at how Missouri is handling cases of inmates sentenced as juveniles to serve life without parole:

WHY IS THIS AN ISSUE?

Five years ago, after already banning the death penalty for juveniles and life without parole for young offenders convicted of crimes other than homicide, the high court barred states from imposing mandatory life-without-parole sentences on anyone under 18 convicted of murder. Several states across America followed up with laws prohibiting such penalties in new cases.

Then in January 2016, the Supreme Court made its ruling retroactive, saying the more than 2,000 offenders already serving such sentences must be given the chance to show their crimes did not reflect "irreparable corruption" and, if not, they should have some hope for freedom.

The court points to research showing that the brains of adolescents are still developing, making them susceptible to peer pressure and likelier to commit reckless acts without considering the long-term impact. To punish youths with the same severity as adults and to then make those sentences mandatory — taking away any discretion to weigh each offender individually — fails to consider that difference or the potential for rehabilitation, the court said in determining that no-release sentences are unconstitutional for all but the rare juvenile whose crimes reflect "permanent incorrigibility."

HOW MANY ARE AFFECTED IN MISSOURI?

Some 94 inmates are serving life without parole for murders committed while they were younger than 18, according to a review of data by the state Department of Corrections. Since last fall, 20 of 23 juvenile lifers who have sought release have been denied it, according to the MacArthur Justice Center, which filed suit this year accusing the Missouri Department of Corrections and the state's parole board of running a system that denies juvenile lifers a fair opportunity for release. That case isn't scheduled to go to trial until November of next year.

WHAT IS MISSOURI'S LAW?

After the Supreme Court's 2012 ruling, Missouri lacked valid sentencing guidelines for juvenile murderers, forcing the state's prosecutors to instead charge young offenders with second-degree murder.

Under a measure signed into law last year by then-Gov. Jay Nixon, a range of terms is now available in first-degree murder cases involving juveniles: life without parole, life with parole eligibility, or a sentence of 30 to 40 years. To impose life without parole, a jury must unanimously agree that prosecutors have proven additional factors, such as torture of the victim.

All Missouri inmates already doing time for first-degree murder committed as juveniles must serve 25 years before getting a parole hearing.

The legislation won broad support, passing 145-1 in the House and unanimously in the Senate.

HOW ARE STATE COURTS ADDRESSING THIS?

The Missouri Supreme Court continues to sort out such cases. On July 11, the court, in a 5-1 ruling, ordered a new sentencing hearing for Jason Carr, who got life in prison for the 1983 killing of his brother, stepmother and stepsister when he was 16. Carr, now 50, received three life terms without possibility of parole for half a century.

Concluding that Carr's sentence violates constitutional protections against cruel and unusual punishment, the state justices said Carr's youth and maturity level at the time of the crime must be weighed in determining whether life without parole for 50 years is fair. If it's not, the trial court must vacate his conviction and instead find him guilty of second-degree murder, which is punishable either by 10 to 30 years or up to life in prison.

Separately, the state's high court found in two other July decisions that it's OK in some cases for juveniles convicted of multiple crimes to serve consecutive sentences that effectively amount to life in prison. The court's majority said the U.S. Supreme Court ruling didn't address the consequences of multiple sentences.