(a) It is an affirmative defense to prosecution that, at the time of the conduct charged, the actor, as a result of severe mental disease or defect, did not know that his conduct was wrong.
(b) The term “mental disease or defect” does not include an abnormality manifested only by repeated criminal or otherwise antisocial conduct.
Acts 1973, 63rd Leg., p. 883, ch. 399, Sec. 1, eff. Jan. 1, 1974. Amended by Acts 1983, 68th Leg., p. 2640, ch. 454, Sec. 1, eff. Aug. 29, 1983; Acts 1993, 73rd Leg., ch. 900, Sec. 1.01, eff. Sept. 1, 1994.