2002—In Atkins v. Virginia, the Court, in an opinion by Justice Stevens (for a majority of six justices), relies on the “direction of change” in state laws, the views of the supposed “world community” and of various professional and religious groups, and polling data to rule that execution of anyone who is even slightly mentally retarded violates the “evolving standards of decency” that it sees as governing application of the Eighth Amendment. (A person who has properly been found competent to stand trial, who is aware of the punishment he is about to suffer and why, and whose subaverage intellectual capacity has been found an insufficiently compelling reason to lessen his responsibility for a crime may nonetheless be “mentally retarded.”)

In dissent, Justice Scalia marvels at the majority’s ability to extract a “national consensus” from the fact that 18 of the 38 states that permit capital punishment have recently enacted legislation barring execution of the mentally retarded. Moreover, Scalia charges, the majority’s assumption that judges and juries are unable to take proper account of mental retardation “is not only unsubstantiated, but contradicts the immemorial belief, here and in England, that they play an indispensable role in such matters.”