1. A defendant is not criminally responsible by reason of insanity if, at the time of the criminal conduct, as a result of mental disease or defect, the defendant lacked substantial capacity to appreciate the wrongfulness of the criminal conduct. [2005, c. 263, §5(AMD).]
2. As used in this section, "mental disease or defect" means only those severely abnormal mental conditions that grossly and demonstrably impair a person's perception or understanding of reality. An abnormality manifested only by repeated criminal conduct or excessive use of alcohol, drugs or similar substances, in and of itself, does not constitute a mental disease or defect. [1985, c. 796, §5(AMD).]
3. Lack of criminal responsibility by reason of insanity is an affirmative defense. [2005, c. 263, §6(NEW).]
1981, c. 324, § 14 (NEW) . 1985, c. 796, § 5 (AMD) . 2005, c. 263, §§5,6 (AMD) .