The law signed Thursday by Corbett means defendants 14 or younger would serve at least 20 years for second-degree convictions and 25 years for first-degree convictions. Offenders who are 15- to 17-years old would face at least 25 or 35 years.
The measure was spurred by the U.S. Supreme Court's decision that recently outlawed mandatory life-without-parole terms for minors, deeming it cruel and unusual punishment.
The Pennsylvania legislation creates a new set of sentencing options, with penalties that depend on the age of the defendant and whether they're convicted of first- or second-degree murder.
Pennsylvania prison officials have estimated the number of juvenile lifers at about 300.