IOWA CITY, Iowa (AP) – The Iowa Supreme Court is banning life prison sentences without the possibility of parole for juveniles convicted of first-degree murder. The court ruled 4-3 Friday that the punishment amounts to cruel and unusual punishment under the Iowa Constitution. Justices ruled in the case of Isaiah Sweet, who was 17 when he killed his custodial grandparents at their Manchester home in 2012.

A judge in 2014 sentenced Sweet to life in prison without parole, saying he was a cold-blooded murderer who had little chance of rehabilitation. Justices overturned that sentence Friday. The court says even the worst juvenile offenders should have the option of someday proving to the parole board they’re fit for release.

The court says judges simply can’t predict whether teens might be rehabilitated at the time of trial.