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.