How did the Supreme Court decision in Roper v. Simmons change the death penalty for juvenile offenders?

The Supreme Court’s 2005 decision in Roper v. Simmons fundamentally changed the juvenile justice landscape by ruling that the death penalty for offenders under the age of 18 is unconstitutional.12

Prior to this ruling, the Court’s 1989 decision in Stanford v. Kentucky had permitted the execution of individuals who were 16 or 17 at the time of their crimes. In Roper, the Court overturned that precedent, determining that executing a person for a crime committed while under the age of 18 constitutes "cruel and unusual punishment" under the Eighth Amendment. The Court held that such a sentence is a disproportionate punishment, effectively establishing 18 as the minimum age for death penalty eligibility in the United States.12

This decision reflected a significant shift away from the trend of increasingly stringent and harsh punishments for juvenile offenders that had characterized the late 20th century. By setting this constitutional floor, the Court affirmed the ethical principle that the diminished culpability and developmental differences of youth must be recognized within the justice system.21