In Atkins v. Virginia (1) the Supreme Court held that the execution of any individual with mental retardation violates the Eighth Amendment's prohibition on cruel and unusual punishment. The holding of Atkins is straightforward: Persons with mental retardation cannot be subject to the death penalty. In keeping with its tradition of allowing the lower courts to determine how new constitutional rules will be implemented, however, the Atkins Court intentionally gave them little direction on how to apply that apparently simple, but profoundly important, prohibition. As the Atkins ruling passes its one-year anniversary, the decision has in consequence presented a number of challenges for the legal community, especially for the appellate courts that will be charged with establishing the procedures used to give effect to its rule.
For states like Alabama, which currently has no statute addressing capital defendants with mental retardation and a legislature that will not reconvene for its regular session until the spring of 2004, appellate courts are likely to make the initial determinations about Atkins and its implications. However, determining mental retardation will require appellate courts to undertake a more complicated analysis than that required by cases like Thompson v. Oklahoma (2) and Coker v. Georgia, (3) which addressed other Eighth-Amendment concerns. This Article explores some of the considerations and challenges that appellate courts and the lawyers that practice before them will face in undertaking the complicated analysis that Atkins requires: What are the constitutional limits on defining mental retardation, how can the legal system avoid the pitfalls inherent in seeking a definitive answer to a fluid concept such as intelligence, and how does the history of mental retardation inform the appellate courts' assessment of mental retardation?
The Atkins Court extended the exemption from execution to all capital defendants who "fall within the range of mentally retarded offenders about whom there is a national consensus," (4) effectively reminding courts that the states cannot create laws to deprive mentally retarded defendants of an exemption guaranteed by the Eighth Amendment; whatever procedures they use to define and prove mental retardation, those procedures must satisfy the Constitution. (5)
However, because the Constitution "'places a substantive restriction on the state's power to take the life' of a mentally retarded offender," (6) the Eighth Amendment also restricts states' ability to stray from the accepted mental-retardation definitions or to establish procedures that restrict advocates' abilities to present evidence of mental retardation. If states deviate significantly from national standards of defining mental retardation, they risk higher courts' concluding that their definitions are outside the national consensus.
II. IQ SCORES AND MENTAL RETARDATION
In fashioning a legal definition of mental retardation, the Atkins Court recognized that state statutory definitions generally conform to the clinical definitions set forth by the American Association on Mental Retardation (AAMR) and the American Psychiatric Association (APA), the two leading organizations that set definitions and standards for determining mental retardation. The three core components of these definitions are (1) significantly subaverage general intellectual functioning (2) that is accompanied by significant limitations in adaptive functioning in at least two of the following skill areas: communication, self-care, home living, social/interpersonal skills, use of community resources, self-direction, functional academic skills, work, leisure, health, and safety, and (3) onset of the condition prior to 18 years of age. (7) Intellectual functioning is weighed equally with adaptive behavior in determining mental retardation. (8)
The APA describes the "significantly subaverage general intellectual functioning" associated with an IQ in the range that includes a score of 70 as "approximately two standard deviations below the mean [score of 100]. …