(1) A person is not responsible for criminal conduct if at the time of such conduct as a result of mental disease or defect he or she lacks adequate capacity either to appreciate the criminality of his or her conduct or to conform his or her conduct to the requirements of law.

(2) The terms "mental disease or defect" do not include an abnormality manifested only by repeated criminal or otherwise anti-social conduct. The terms "mental disease or defect" shall include congenital and traumatic mental conditions as well as disease.