Introduction

On March 1, 2005, the United States Supreme Court ruled that executing those who were under the age of 18, at the time of the crime, had become “cruel and unusual punishment” prohibited by the Eighth Amendment to the US Constitution (Roper v. Simmons, 125 S.Ct. 1183 [2005]). There has been criticism, by some, of the Court's legal reasoning in coming to that decision (e.g., so-called “judicial activism,” incorrect Eighth Amendment analysis, improper consideration of foreign law). However, few have argued with Justice Kennedy's conclusion as to the “diminished culpability of juveniles.” (Simmons, 2005, p. 1196). Adolescents are simply not as responsible as fully formed adults who commit similar crimes.

The Supreme Court's Eighth Amendment analysis in death penalty cases is based on two principles. The first, a fundamentally legal one, is whether “standards of decency” have evolved to the point where there is now national consensus that a particular form of punishment has become cruel and unusual. A second issue the Court has to address is whether the constitutionally legitimate purposes of the death penalty – retribution and deterrence – are applicable to this particular group of offenders. In coming to a conclusion regarding the level of culpability, and therefore the appropriate punishment, for 16- and 17-year-old offenders, the Court had to look outside the law and to science.