Mich. Comp. Laws » Michigan Compiled Laws / Chapter 768 / Act 175 of 1927
Michigan Compiled Laws

Mich. Comp. Laws § 768.21a (2026)

Persons deemed legally insane; burden of proof.

✓ current as of July 2026
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THE CODE OF CRIMINAL PROCEDURE


Act 175 of 1927


768.21a Persons deemed legally insane; burden of proof.

Sec. 21a.

    (1) It is an affirmative defense to a prosecution for a criminal offense that the defendant was legally insane when he or she committed the acts constituting the offense. An individual is legally insane if, as a result of mental illness as defined in section 400 of the mental health code, 1974 PA 258, MCL 330.1400, or as a result of having an intellectual disability as defined in section 100b of the mental health code, 1974 PA 258, MCL 330.1100b, that person lacks substantial capacity either to appreciate the nature and quality or the wrongfulness of his or her conduct or to conform his or her conduct to the requirements of the law. Mental illness or having an intellectual disability does not otherwise constitute a defense of legal insanity.

    (2) An individual who was under the influence of voluntarily consumed or injected alcohol or controlled substances at the time of his or her alleged offense is not considered to have been legally insane solely because of being under the influence of the alcohol or controlled substances.

    (3) The defendant has the burden of proving the defense of insanity by a preponderance of the evidence.

History: Add. 1975, Act 180, Eff. Aug. 6, 1975 ;-- Am. 1994, Act 56, Eff. Oct. 1, 1994 ;-- Am. 2014, Act 76, Imd. Eff. Mar. 28, 2014

Notes of Decisions
Cited in 159 cases (48 in the last 5 years), 1978–2026 · leading case: People v. Carpenter, 627 N.W.2d 276 (Mich. 2001).
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People v. Carpenter, 627 N.W.2d 276 (Mich. 2001). · cites it 16× “§ 768.36. [16] See Morse, Undiminished confusion in diminished capacity, 75 J Crim L & Criminology 1, 6 (1984).”
People v. Fackelman, 802 N.W.2d 552 (Mich. 2011). · cites it 14× “Shahid’s report, including his diagnosis, clearly constituted hearsay.”
People v. Grant, 520 N.W.2d 123 (Mich. 1994). · cites it 6× “800(500)(g)][ [16] ] and in [MCL 768.21a; MSA 28.1044(1)] of chapter 8 of this act.”
People v. Toma, 613 N.W.2d 694 (Mich. 2000). · cites it 6× “[MCL 768.21a; MSA 28.1044(1).] [12] The statute defining the psychologist-patient privilege, in relevant part, provides: A psychologist licensed or allowed to use that title under this part or an individual under his or her supervision cannot be compelled to disclose…”
People v. Stephan, 616 N.W.2d 188 (Mich. Ct. App. 2000). · cites it 11× “MCL 768.21a; MSA 28.1044(1); CJI2d 7.11. However, the Criminal Jury Instruction for GBMI verdicts, consistent with the nonamended GBMI statute, continues to place the burden of proof on the prosecutor to show beyond a reasonable doubt that the defendant was not insane.”
People v. Ramsey, 375 N.W.2d 297 (Mich. 1985). · cites it 6× “MCL 768.21a; MSA 28.1044(1) defines insanity: A person is legally insane if, as a result of mental illness .”
People v. Lacalamita, 780 N.W.2d 311 (Mich. Ct. App. 2009). · cites it 2× “” MCL 768.21a(3). [Emphasis in original.] A “mental illness” is defined as “a substantial disorder of thought or mood that significantly impairs judgment, behavior, capacity to recognize reality, or ability to cope with the ordinary demands of life.”
People v. Conrad, 385 N.W.2d 277 (Mich. Ct. App. 1986). · cites it 6× “' MCL 768.21a; MSA 28.1044(1). Under these definitions, one must be mentally ill before he can be found insane, but the converse is not true.”
People v. Mette, 621 N.W.2d 713 (Mich. Ct. App. 2001). · cites it 2× “[MCL 768.21a; MSA 28.1044(1).] Mental illness is now defined in MCL 330.”
People v. Hayes, 364 N.W.2d 635 (Mich. 1985). · cites it 2× “In MCL 768.20a(4); MSA 28.1043(1)(4), it is clearly the Legislature's intent to give discretion to the trial court to determine whether the defense should be barred on the basis of a failure to cooperate.”
People v. Hardesty, 362 N.W.2d 787 (Mich. Ct. App. 1984). · cites it 4× “" MCL 768.21a(1); MSA 28.1044(1)(1). Thus, whether or not he was mentally ill, a defendant is legally sane if he had substantial capacity both to appreciate the wrongfulness of his conduct and to conform his conduct to the requirements of the law.”
People v. Webb, 580 N.W.2d 884 (Mich. 1998). · cites it 2× “§ 768.21a(1); M.S.A. § 28.1044(1)(1) provided that a person "is legally insane if, as a result of mental illness as defined in [M.”
Show all 159 citing cases →
— Mich. Comp. Laws § 768.21a(1) — 95 cases
People v. Fackelman, 802 N.W.2d 552 (Mich. 2011). “Shahid’s report, including his diagnosis, clearly constituted hearsay.”
People v. Grant, 520 N.W.2d 123 (Mich. 1994). “800(500)(g)][ [16] ] and in [MCL 768.21a; MSA 28.1044(1)] of chapter 8 of this act.”
People v. Carpenter, 627 N.W.2d 276 (Mich. 2001). “§ 768.36. [16] See Morse, Undiminished confusion in diminished capacity, 75 J Crim L & Criminology 1, 6 (1984).”
People v. Crawford, 279 N.W.2d 560 (Mich. Ct. App. 1979).
People v. Dobben, 488 N.W.2d 726 (Mich. 1992).
— Mich. Comp. Laws § 768.21a(2) — 26 cases
People v. Carpenter, 627 N.W.2d 276 (Mich. 2001). “§ 768.36. [16] See Morse, Undiminished confusion in diminished capacity, 75 J Crim L & Criminology 1, 6 (1984).”
People v. Grant, 520 N.W.2d 123 (Mich. 1994). “800(500)(g)][ [16] ] and in [MCL 768.21a; MSA 28.1044(1)] of chapter 8 of this act.”
People v. Shahideh, 758 N.W.2d 536 (Mich. 2008).
People v. Conrad, 385 N.W.2d 277 (Mich. Ct. App. 1986). “' MCL 768.21a; MSA 28.1044(1). Under these definitions, one must be mentally ill before he can be found insane, but the converse is not true.”
People v. Matulonis, 320 N.W.2d 238 (Mich. Ct. App. 1982).
— Mich. Comp. Laws § 768.21a(3) — 38 cases
People v. Fackelman, 802 N.W.2d 552 (Mich. 2011). “Shahid’s report, including his diagnosis, clearly constituted hearsay.”
People v. Carpenter, 627 N.W.2d 276 (Mich. 2001). “§ 768.36. [16] See Morse, Undiminished confusion in diminished capacity, 75 J Crim L & Criminology 1, 6 (1984).”
People v. Lacalamita, 780 N.W.2d 311 (Mich. Ct. App. 2009). “” MCL 768.21a(3). [Emphasis in original.] A “mental illness” is defined as “a substantial disorder of thought or mood that significantly impairs judgment, behavior, capacity to recognize reality, or ability to cope with the ordinary demands of life.”
People v. Mette, 621 N.W.2d 713 (Mich. Ct. App. 2001). “[MCL 768.21a; MSA 28.1044(1).] Mental illness is now defined in MCL 330.”
Johnigan v. Elo, 207 F. Supp. 2d 599 (E.D. Mich. 2002).
— Mich. Comp. Laws § 768.21a(l) — 16 cases
People v. Lacalamita, 780 N.W.2d 311 (Mich. Ct. App. 2009). “” MCL 768.21a(3). [Emphasis in original.] A “mental illness” is defined as “a substantial disorder of thought or mood that significantly impairs judgment, behavior, capacity to recognize reality, or ability to cope with the ordinary demands of life.”
People v. Fackelman, 802 N.W.2d 552 (Mich. 2011). “Shahid’s report, including his diagnosis, clearly constituted hearsay.”
People v. Carpenter, 627 N.W.2d 276 (Mich. 2001). “§ 768.36. [16] See Morse, Undiminished confusion in diminished capacity, 75 J Crim L & Criminology 1, 6 (1984).”
Orzel v. Scott Drug Co., 537 N.W.2d 208 (Mich. 1995).
People v. Hardesty, 362 N.W.2d 787 (Mich. Ct. App. 1984). “" MCL 768.21a(1); MSA 28.1044(1)(1). Thus, whether or not he was mentally ill, a defendant is legally sane if he had substantial capacity both to appreciate the wrongfulness of his conduct and to conform his conduct to the requirements of the law.”
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