NOTE: The statutes listed in this chart were all passed prior to the United States Supreme Court Ruling in Atkins v. Virginia. During this time period, intellectual disability was referred to as “mental retardation”.

State Statute Citation Definition of Mental Retardation Qualified Examiners
Arizona Ariz. Rev. Stat. Sect. 13-3982 A condition based on a mental deficit that has resulted in significantly subaverage general intellectual functioning existing concurrently with significant limitations in adaptive functioning, where the onset of the forgoing conditions occurred before the defendant reached the age of eighteen. Requires the trial court in a capital case to appoint a licensed psychologist to conduct a prescreening evaluation to determine the defendant’s IQ.
Arkansas Ark. Code Ann. Sect. 5-4-618 (1993) Significantly subaverage general intellectual functioning accompanied by significant deficits or impairments in adaptive functioning, and manifested in the developmental period. The age of onset is 18. There is a rebuttable presumption of mental retardation when the defendant has an IQ of 65 or below. There is no information on this aspect of the statute.
Colorado Colo. Rev. Stat. Sect. 16-9-401-403 Any defendant with significantly subaverage general intellectual functioning existing concurrently with substantial deficits in adaptive behavior and manifested and documented during the developmental period. The requirements for documentation may be excused by the court upon a finding that extraordinary circumstances exist. The court does not define extraordinary circumstances. The law does not give a numerical IQ level. There is no information on this aspect of the statute.
Connecticut (death penalty abolished) Public Act No, 01-151 Significantly subaverage general intellectual functioning existing concurrently with deficits in adaptive behavior and manifested during the developmental period. (as defined in Conn. Gen. Stat. § 1-1g (2001)) There is no information on this aspect of the statute.
Florida Florida Statutes, Sect. 921.137 Significantly subaverage general intellectual functioning existing concurrently with deficits in adaptive behavior and manifested during the period from conception to age 18. Court-appointed experts in the field of mental retardation shall evaluate the defendant and report their findings to the court and all interested parties prior to the final sentencing hearing.
Georgia Ga. Code. Ann. Sect. 17-7-131(i) “…Significantly subaverage intellectual functioning resulting in or associated with impairments in adaptive behavior which manifests during the developmental period.”* Court-appointed licensed psychologists or psychiatrists; or physicians or licensed clinical psychologists chosen and paid for by the defendant.
Indiana Ind. Code Sect. 35-36-9-1 et. seq. An individual before becoming 22 years of age manifests: (1) significantly subaverage intellectual functioning; and (2) substantial impairment of adaptive behavior that is documented in a court-ordered evaluative report. State does not specify if the court can appoint psychologists or psychiatrists. Attorneys should probably obtain this information from trial court at pre-trial.
Kansas Kan. Stat. Ann. Sect. 21-4623 An individual having significantly subaverage general intellectual functioning to an extent that substantially impairs one’s capacity to appreciate the criminality of one’s conduct or conform one’s conduct to the requirements of law. The statute does not define adaptive behavior or the age of onset. However, Kan. Stat. Ann Sect. 76-12b01 defines these terms. Adaptive behavior refers to the effectiveness of personal independence and social responsibility expected of that person’s age, cultural group and community. The age of onset must be prior to 18 years old. There is no information on this aspect of the statute.
Kentucky Ky. Rev. Stat. Sect. 532.130-140 A significant subaverage intellectual functioning existing concurrently with substantial deficits in adaptive behavior and manifested during the developmental period. The age of onset is 18 years old. Significantly subaverage general intellectual functioning is defined as an IQ of 70 or below.* There is no information on this aspect of the statute.
Maryland (death penalty abolished) Md. Code. Ann. art. 27 Sect.412 An individual who has significantly subaverage intellectual functioning as evidenced by an IQ of 70 or below on an individually administered IQ test, and impairment in adaptive behavior. The age of onset is before the age of 22. There is no information on this aspect of the statute.
Missouri RSMo 565.030 Significantly subaverage general intellectual functioning which originates before age eighteen; and is associated with a significant impairment in adaptive behavior. There is no information on this aspect of the statute.
NebraskaR.R.S. Neb. Sect. 28-105.01 (2000)Mental retardation means significantly subaverage general intellectual functioning existing concurrently with deficits in adaptive behavior. An IQ of 70 or below on a reliably administered IQ test shall be presumptive evidence of mental retardation.There is no information on this aspect of the statute.
New Mexico (death penalty abolished) N.M. Stat. Ann. Sect. 31-20A-2.1 (1978) Mental retardation refers to significantly subaverage general intellectual functioning existing concurrently with deficits in adaptive behavior. An IQ of 70 or below on a reliably administered IQ test shall be presumptive evidence of mental retardation. There is no information on this aspect of the statute.
New York
(except for murder by a prisoner) (death penalty abolished)		 N.Y. Crim. Proc. Sect. 400.27(12) The statute uses the most recent American Association on Mental Retardation definition (1992).** The N.Y Statute does not list specific levels of intelligence, nor does it go into detail regarding adaptive skills. No specifics noted - “Psychiatrist, psychologist or other trained individual.”
North Carolina 2001 N.C. Sess. Laws 346 Significantly subaverage general intellectual functioning (defined as having an IQ of 70 or below), existing concurrently with significant limitations in adaptive functioning (defined as having significant limitations in two or more of the following adaptive skill areas: communication, self-care, home living, social skills, community use, self-direction, health and safety, functional academics, leisure skills and work skills) both of which were manifested before the age of 18. A licensed psychiatrist or psychologist.
South Dakota S.D. Codified Laws Sect. 23A-27A-26.1 (2000) Mental retardation means significant subaverage general intellectual functioning existing concurrently with substantial related deficits in applicable adaptive skill areas. An IQ exceeding 70 on a reliable standardized measure of intelligence is presumptive evidence that the defendant does not have significant subaverage general intellectual functioning. Mental retardation must have been manifested and documented before the age of 18 years. A psychiatrist, licensed psychologist, or licensed psychiatric social worker designated by the state’s attorney, for the purpose of rebutting evidence offered by the defendant.
Tennessee Tenn. Code. Ann. tit.39. Ch. 13 pt. 2 sect. 39-13-203 (1) Significantly subaverage general intellectual functioning as evidenced by a functional IQ of 70 or below; (2) deficits in adaptive behavior; (3) the mental retardation must have been manifested during the developmental period or by age 18. The state does not define “deficits in adaptive behavior.” The statute clearly provides that adaptive behavior and intellectual functioning are independent criteria. There is no information on this aspect of the statute.
Washington Was. Rev. Code Ann. Sect. 10.95.030 (West) The individual has (1) significantly subaverage general intellectual functioning; (2) existing concurrently with deficits in adaptive behavior; and (3) both significantly subaverage general intellectual functioning and deficits in adaptive behavior were manifested during the developmental period. The age of onset is 18 years of age. The required IQ level is 70 or below.* A court-appointed licensed psychiatrist or psychologist experienced in the diagnosis and evaluation of metal retardation. This leaves open the issue of whether or not the defendant may hire his own expert.
Federal Government 18 U.S.C.A. Sect. 3596(c) (Federal Crime Bill of 1994) In 1994, Congress adopted legislation to ban the execution of individuals with mental retardation. The statute states that a sentence of death shall not be carried out upon a person who has mental retardation. The statute does not define mental retardation, or discuss at what stage in the criminal proceedings the determination of mental retardation must be made. Earlier, Congress had also provided a form of an exemption for this issue in the Anti-Drug Abuse Act of 1988 (pub. L. No. 100-690).

* AAMR 1983 definition; see Grossman, H. “Manual on Terminology and Classification” (8th ed.) AAMR 1983

** “Mental retardation refers to substantial limitations in present functioning. It is characterized by significantly subaverage intellectual functioning, existing concurrently with related limitations in two or more of the following applicable adaptive skill areas: communication, self-care, home living, social skills, community use, self-direction, health and safety, functional academics, leisure, and work. Mental retardation manifests before age 18.” (Luckasson, R., et. al. “Mental Retardation: Definition, Classification , and Systems of Supports” (9th ed.) AAMR (1992))

Source: Denis W. Keyes and William J. Edwards, “Mental Retardation and the Death Penalty: Current Status of Exemption Legislation,” 687 Mental & Physical Disabilities Law Reporter (September - October 1997) with updated information for Arizona, Nebraska and South Dakota by DPIC.