The U.S. Supreme Court's decision in Atkins v. Virginia (2002) banned the execution of MR offenders as cruel and unusual punishment, a violation of the eighth amendment. The Court adopted the 1992 definition of MR used by the American Association on Mental Retardation: "Mental retardation refers to substantial limitation in present functioning. It is characterized by significantly subaverage intellectual functioning ...." The definition goes on to indicate that MR is characterized by limitations in two or more of a list of social and functional handicaps. Following the overview of the U.S. Supreme Court's Atkins decision, this article reviews the history of the role of psychology in the classification of intelligence and hence legal competence. This includes discussions of historic court cases that have involved clinical measures of intelligence in determining legal issues. One of those cases was City of Cleburne v. Cleburne Living Center (1985), in which the U.S. Supreme Court addressed community resistance to group homes for MR individuals. The ruling struck down zoning ordinances that discriminate against MR individuals, but also held that mental retardation does not in itself warrant special legal rights beyond those afforded all citizens. The implication of this latter finding was to change mental retardation from an Axis I major clinical syndrome to Axis II, beginning with the 1987 DSM-III-R. This classification shift made MR defendants "death qualified." The issue was clarified, however, in the "Atkins" decision. 45 references