Ky. Rev. Stat. » Chapter 504
Kentucky Revised Statutes

Ky. Rev. Stat. § 504.020 (2026)

Mental illness or intellectual disability

✓ current as of May 2026
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(1) A person is not responsible for criminal conduct if at the time of such conduct, as a result of mental illness or intellectual disability, he lacks substantial capacity either to appreciate the criminality of his conduct or to conform his conduct to the requirements of law. (2) As used in this chapter, the term "mental illness or intellectual disability" does not include an abnormality manifested only by repeated criminal or otherwise antisocial conduct. (3) A defendant may prove mental illness or intellectual disability, as used in this section, in exculpation of criminal conduct. Effective: July 12, 2012 History: Amended 2012 Ky. Acts ch. 146, sec. 120, effective July 12, 2012. -- Amended 1988 Ky. Acts ch. 283, sec. 8, effective July 15, 1988. -- Created 1974 Ky. Acts ch. 406, sec. 39, effective January 1, 1975.

Notes of Decisions
Cited in 47 cases (6 in the last 5 years), 1977–2026 · leading case: Noakes v. Commonwealth, 354 S.W.3d 116 (Ky. 2011).
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Noakes v. Commonwealth, 354 S.W.3d 116 (Ky. 2011). · cites it 6× “020, which provides in pertinent part: (1) A person is not responsible for criminal conduct if at the time of such conduct, as a result of mental illness or retardation, he lacks substantial capacity either to appreciate the criminality of his conduct or to conform his conduct…”
Ice v. Commonwealth, 667 S.W.2d 671 (Ky. 1984). · cites it 4× “In Kentucky, we adhere to the rule that insanity is a defense available to the defendant "in exculpation of criminal conduct (KRS 504.020(3))." KRS 500.070(3) provides that the defendant "has the burden of proving" those elements of the case "in exculpation of his conduct.”
Clark v. Arizona, 548 U.S. 735 (2006). · cites it 2× “16 Ark. Code Ann. §5–2–312 (2006); Conn. Gen. Stat.”
Eugene Williams Gall, Jr. v. Phil Parker, Warden, 231 F.3d 265 (6th Cir. 2000). · cites it 3× “KRS 504.020. If the jury had a reasonable doubt that the defendant had been proved not to have acted under the influence of extreme emotional disturbance for which there was a reasonable justification or excuse under the circumstances as she believed them to be, the punishment…”
Kahler v. Kansas, 140 S. Ct. 1021 (2020). · cites it 2× “" Ky. Rev. Stat. Ann. § 504.020 (1) (West 2016).”
Bowling v. Commonwealth, 163 S.W.3d 361 (Ky. 2005). · cites it 2× “, the mental illness or retardation defense described in KRS 504.020, the subjective elements of the KRS Chapter 503 defenses and of extreme emotional disturbance under KRS 507.”
Cannon v. Commonwealth, 777 S.W.2d 591 (Ky. 1989). · cites it 4× “The Kentucky statute relating to, and setting forth the principle of insanity that was in effect at the time of the commission of the alleged crimes that are the subject of this appeal, is KRS 504.020. It provides as follows: "Mental disease or defect — (1) A person is not…”
Sanders v. Commonwealth, 801 S.W.2d 665 (Ky. 1990). · cites it 2× “Appellant next urges that inclusion in the instruction on insanity of the statutory language from KRS 504.020, that "the term mental disease or defect does not *680 include an abnormality manifested only by repeated criminal or otherwise antisocial conduct," had the effect of…”
Weaver v. Commonwealth, 298 S.W.3d 851 (Ky. 2009). · cites it 4× “2d at 369 ("At issue is whether drug addiction is a mental disease, defect, or illness for purposes of KRS 504.020.") KRS 504.020(1) provides that: "A person is not responsible for criminal conduct if at the time of such conduct, as a result of mental illness or retardation, he…”
Bishop v. Caudill, 118 S.W.3d 159 (Ky. 2003). · cites it 2× “KRS 504.020 provides that "mental illness" and "insanity" exculpate criminal behavior: (1) A person is not responsible for criminal conduct if at the time of such conduct, as a result of mental illness or retardation, he lacks substantial capacity either to appreciate the…”
Biyad v. Commonwealth, 392 S.W.3d 380 (Ky. 2013). · cites it 6× “Butler to exculpate him of criminal conduct pursuant to KRS 504.020, the burden of disproving that he was “insane” shifted to the Commonwealth.”
Jewell v. Commonwealth, 549 S.W.2d 807 (Ky. 1977). · cites it 2× “He claims errors in the following three particulars: (1) Rejection of evidence pertinent to his affirmative defense of insanity under KRS 504.020; (2) Reception of evidence relating to his intoxication in terms of the presumptions enacted in KRS 189.”
Show all 47 citing cases →
— Ky. Rev. Stat. § 504.020(1) — 18 cases
Cecil v. Commonwealth, 888 S.W.2d 669 (Ky. 1994).
Weaver v. Commonwealth, 298 S.W.3d 851 (Ky. 2009). “2d at 369 ("At issue is whether drug addiction is a mental disease, defect, or illness for purposes of KRS 504.020.") KRS 504.020(1) provides that: "A person is not responsible for criminal conduct if at the time of such conduct, as a result of mental illness or retardation, he…”
Nationwide Mut. Fire Ins. Co. v. Pelgen, 241 S.W.3d 814 (Ky. Ct. App. 2008).
Brewster v. Commonwealth, 568 S.W.2d 232 (Ky. 1978).
Star v. Commonwealth, 313 S.W.3d 30 (Ky. 2010).
— Ky. Rev. Stat. § 504.020(2) — 1 case
Noakes v. Commonwealth, 354 S.W.3d 116 (Ky. 2011). “020, which provides in pertinent part: (1) A person is not responsible for criminal conduct if at the time of such conduct, as a result of mental illness or retardation, he lacks substantial capacity either to appreciate the criminality of his conduct or to conform his conduct…”
— Ky. Rev. Stat. § 504.020(3) — 2 cases
Ice v. Commonwealth, 667 S.W.2d 671 (Ky. 1984). “In Kentucky, we adhere to the rule that insanity is a defense available to the defendant "in exculpation of criminal conduct (KRS 504.020(3))." KRS 500.070(3) provides that the defendant "has the burden of proving" those elements of the case "in exculpation of his conduct.”
Eugene Williams Gall, Jr. v. Phil Parker, Warden, 231 F.3d 265 (6th Cir. 2000). “KRS 504.020. If the jury had a reasonable doubt that the defendant had been proved not to have acted under the influence of extreme emotional disturbance for which there was a reasonable justification or excuse under the circumstances as she believed them to be, the punishment…”
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