Final answer:
The U.S. Supreme Court struck down the death penalty for those under 18 in 2005 in the Roper v. Simmons case.
Step-by-step explanation:
In 2005, the U.S. Supreme Court rendered a landmark decision in Roper v. Simmons, fundamentally altering the landscape of capital punishment in the United States.
This case specifically addressed the constitutionality of imposing the death penalty on individuals who were under the age of 18 at the time of their crimes. In a 5-4 decision, the Court ruled that executing juvenile offenders constituted cruel and unusual punishment, in violation of the Eighth Amendment.
Justice Anthony Kennedy, writing for the majority, emphasized the evolving standards of decency in society and the international consensus against executing juvenile offenders. The Court's decision in Roper v. Simmons built upon previous rulings, such as Atkins v. Virginia, which barred the execution of individuals with intellectual disabilities.
This decision marked a significant departure from the Court's earlier stance in cases like Stanford v. Kentucky (1989), which upheld the constitutionality of executing 16- and 17-year-olds.
Roper v. Simmons reflected a growing recognition of the immaturity and diminished culpability of juveniles, acknowledging that they should not be held to the same level of moral and legal responsibility as adults in the context of capital punishment.
As a result, the ruling set a precedent and underscored the Court's commitment to safeguarding the rights and protections afforded by the Constitution, particularly in cases involving the most severe penalties.