The Supreme Court decided that it is unconstitutional to execute any person who is younger than eighteen at the time of committing a capital offense.

Since the 1950’s, the Supreme Court has recognized that the meaning of “cruel and unusual punishment” is determined by “evolving standards” of decency that reflect societal values. In Stanford v. Kentucky[c]Stanford v. Kentucky (1989), the justices allowed the imposition of capital punishment on an offender who was only sixteen years old at the time of the crime. A few years later, however, in Atkins v. Virginia[c]Atkins v. Virginia (2003), they decided that society’s standards of decency had evolved to the extent that the execution of the mentally retarded had become unconstitutional.

Christopher Simmons was sentenced to death for a murder he committed at the age of seventeen. Based on the reasoning used in the Atkins decision, however, the Missouri Supreme Court ruled that the execution of minors was unconstitutional. The ruling was then appealed to the U.S. Supreme Court.

By a 5-4 vote, the Court upheld the ruling of Missouri’s high court. Writing for the majority, Justice Anthony M. KennedyKennedy, Anthony M.;Roper v. Simmons based the ruling on four major considerations. First, Kennedy inferred a national consensus, given that three-fifths of the states no longer utilize the death penalty against minors, whereas only three states in the last ten years had actually executed minors. Secondly, a large body of scientific evidence finds that in comparison with adults, juveniles lack maturity and a sense of responsibility, and that they are much more vulnerable to outside pressures and negative influences. Thirdly, international opinion is overwhelmingly against the execution of juveniles. Finally, Kennedy found that drawing the line at eighteen was reasonable because it is where government draws the line at adulthood for numerous other purposes. The four dissenting justices were particularly unhappy with Kennedy’s references to foreign sources for references.

Capital punishment

Furman v. Georgia

Gregg v. Georgia

McCleskey v. Kemp