Which case ruled that the death penalty for individuals under 18 is unconstitutional?

The ruling in the case of Roper v. Simmons is significant because it established that the death penalty is unconstitutional for individuals who were under the age of 18 at the time of their crime. This decision was grounded in the Eighth Amendment's prohibition against cruel and unusual punishment. The Supreme Court held that juveniles possess a lesser degree of culpability compared to adults due to their developmental immaturity, which affects their judgment and behavior.

The ruling reinforced that the evolving standards of decency in society do not support the execution of minors, reflecting a growing consensus against such practices. Consequently, this case effectively set a legal precedent that aligns with the understanding of juveniles' capacity for change and rehabilitation.

In contrast, other cases mentioned do not address the constitutionality of the death penalty for juveniles in the same definitive manner, focusing instead on different legal principles or issues related to juvenile rights and treatment under the law.