A National Survey of State Legislation defining mental retardation: implications for policy and practice after Atkins.

In Atkins v. Virginia 2002, the U.S. Supreme Court held that the Eighth Amendment prohibits executing offenders who are mentally retarded. Rather than adopting a uniform definition of mental retardation, the court charged each state with defining mental retardation in a manner that enforces the constitutional restriction. An unanswered question is how states define mental retardation after Atkins, which has implications for capital defendants and forensic evaluators who conduct capital mitigation evaluations. This project identified the statutory definitions of mental retardation in each state, and grouped the definitions based on consistency with accepted clinical criteria for mental retardation. Results show that definitions of mental retardation vary considerably by state. The large majority of states, both overall and specifically among death penalty states, use criteria for mental retardation that are not entirely consistent with accepted clinical standards. As such, it is not clear whether the majority of states are effectuating the intent of Atkins. The implications of these findings for both policy and practice are discussed.