Delaware Code

11 Del. C. § 401 (2026)

Mental illness or psychiatric disorder

✓ current as of May 2026

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(a) In any prosecution for an offense, it is an affirmative defense that, at the time of the conduct charged, as a result of mental illness or serious mental disorder, the accused lacked substantial capacity to appreciate the wrongfulness of the accused’s conduct. If the defendant prevails in establishing the affirmative defense provided in this subsection, the trier of fact shall return a verdict of “not guilty by reason of insanity.”

(b) Where the trier of fact determines that, at the time of the conduct charged, a defendant suffered from a mental illness or serious mental disorder which substantially disturbed such person’s thinking, feeling or behavior and/or that such mental illness or serious mental disorder left such person with insufficient willpower to choose whether the person would do the act or refrain from doing it, although physically capable, the trier of fact shall return a verdict of “guilty, but mentally ill.”

(c) It shall not be a defense under this section if the alleged insanity or mental illness was proximately caused by the voluntary ingestion, inhalation or injection of intoxicating liquor, any drug or other mentally debilitating substance, or any combination thereof, unless such substance was prescribed for the defendant by a licensed health-care practitioner and was used in accordance with the directions of such prescription. As used in this chapter, the terms “insanity” or “mental illness” do not include an abnormality manifested only by repeated criminal or other antisocial conduct.

11 Del. C. 1953, § 401; 58 Del. Laws, c. 497, § 1; 63 Del. Laws, c. 328, § 1; 70 Del. Laws, c. 186, § 1; 76 Del. Laws, c. 141, §§ 1, 2; 78 Del. Laws, c. 224, §§ 2, 3;

Notes of Decisions

Cited in 15 cases (7 in the last 5 years), 1976–2026 · leading case: Smith v. Delaware, 236 F. Supp. 3d 882 (D. Del. 2017).

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Smith v. Delaware, 236 F. Supp. 3d 882 (D. Del. 2017). · cites it 2× “I; 3 at 2) Plaintiff alleges that the State violated his constitutional rights by equating 11 Del. C. § 401 6 with being *886 aware of his predicament and appreciation of his charges.”

Rivera v. State, 351 A.2d 561 (Del. 1976). · cites it 3× “She attacks, as violative of the Due Process Clause, 11 Del.C. § 401 1 classifying mental illness as an affirmative defense which the defendant must prove by a preponderance of the evidence under 11 Del.”

Hand v. State, 354 A.2d 140 (Del. 1976). · cites it 2× “Finally, the defendant attacks the constitutionality of 11 Del.C. § 401, classifying mental illness as an affirmative defense 3 as to which the defendant has the burden of proof.”

United States Ex Rel. Hand v. Redman, 416 F. Supp. 1109 (D. Del. 1976). “11 Del.C. § 401 provides: “(a) In any prosecution for an offense, it is an affirmative defense that, at the time of the conduct charged, as a result of mental illness or mental defect, the accused lacked substantial capacity to appreciate the wrongfulness of his conduct or…”

State v. Tarbutton, 407 A.2d 538 (Del. Super. Ct. 1979). · cites it 2× “11 Del.C. § 401 provides: (a) In any prosecution for an offense, it is an affirmative defense that, at the time of the conduct charged, as a result of mental illness or mental defect, the accused lacked substantial capacity to appreciate the wrongfulness of his conduct or lacked…”

State v. Dorsett (Del. Super. Ct. 2019). · cites it 8× “The Supreme Court has held that GBMI is not an affirmative defense but a verdict or 8 11 Del. C. §401(a). 8 finding made by the trier of fact.”

Cooke v. State (Del. 2025). · cites it 4× “”31 The source of this disagreement was defense counsel’s view that Cooke could maintain his innocence at trial while counsel could simultaneously urge the jury to find Cooke guilty but mentally ill (“GBMI”) under 11 Del. C. § 401(b).32 Defense counsel was of the view that…”

Calhoun v. State (Del. 2020). · cites it 2× “” 11 Del. C. § 401(b). Under 11 Del. C. § 401(c), it is not a defense “if the alleged insanity or mental illness was proximately caused by the voluntary ingestion, inhalation or injection of intoxicating liquor, any drug or other mentally debilitating substance, or any…”

Smith v. State (Del. Super. Ct. 2025). · cites it 2× “Mechanick, reviewed the defense experts’ reports, interviewed Smith, and agreed that Smith qualified as GBMI under 11 Del. C. § 401(b) because his mental illness “affected his thinking, feeling, or action at the time of the crime.”

Taylor v. State (Del. 2019). “28 27 11 Del. C. § 401(b). 28 11 Del. C. § 408(a) (emphasis added).”

Waples v. State (Del. 2021). “16 11 Del. C. § 401(a). 17 Id. § 401(b). 18 Williams v.”

State v. Stephenson (Del. Super. Ct. 2021). “By pursuing a 18 11 Del. C.§ 401(b). 7 sufficiency of the evidence defense, Stephenson was convicted of the lesser Murder in the Second Degree.”

Show all 15 citing cases →

— 11 Del. C. § 401(a) — 5 cases

State v. Tarbutton, 407 A.2d 538 (Del. Super. Ct. 1979). “11 Del.C. § 401 provides: (a) In any prosecution for an offense, it is an affirmative defense that, at the time of the conduct charged, as a result of mental illness or mental defect, the accused lacked substantial capacity to appreciate the wrongfulness of his conduct or lacked…”

State v. Dorsett (Del. Super. Ct. 2019). “The Supreme Court has held that GBMI is not an affirmative defense but a verdict or 8 11 Del. C. §401(a). 8 finding made by the trier of fact.”

Waples v. State (Del. 2021). “16 11 Del. C. § 401(a). 17 Id. § 401(b). 18 Williams v.”

State v. Topolski (Del. Super. Ct. 2023).

State v. Earl (Del. Super. Ct. 2026).

— 11 Del. C. § 401(b) — 6 cases

State v. Dorsett (Del. Super. Ct. 2019). “The Supreme Court has held that GBMI is not an affirmative defense but a verdict or 8 11 Del. C. §401(a). 8 finding made by the trier of fact.”

Cooke v. State (Del. 2025). “”31 The source of this disagreement was defense counsel’s view that Cooke could maintain his innocence at trial while counsel could simultaneously urge the jury to find Cooke guilty but mentally ill (“GBMI”) under 11 Del. C. § 401(b).32 Defense counsel was of the view that…”

Smith v. State (Del. Super. Ct. 2025). “Mechanick, reviewed the defense experts’ reports, interviewed Smith, and agreed that Smith qualified as GBMI under 11 Del. C. § 401(b) because his mental illness “affected his thinking, feeling, or action at the time of the crime.”

Taylor v. State (Del. 2019). “28 27 11 Del. C. § 401(b). 28 11 Del. C. § 408(a) (emphasis added).”

Calhoun v. State (Del. 2020). “” 11 Del. C. § 401(b). Under 11 Del. C. § 401(c), it is not a defense “if the alleged insanity or mental illness was proximately caused by the voluntary ingestion, inhalation or injection of intoxicating liquor, any drug or other mentally debilitating substance, or any…”

— 11 Del. C. § 401(c) — 4 cases

State v. Dorsett (Del. Super. Ct. 2019). “The Supreme Court has held that GBMI is not an affirmative defense but a verdict or 8 11 Del. C. §401(a). 8 finding made by the trier of fact.”

State v. Cooke, Jr. (Del. Super. Ct. 2022).

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