Ind. Code § 35-41-3-6 – Mental disease or defect

(a) A person is not responsible for having engaged in prohibited conduct if, as a result of mental disease or defect, he was unable to appreciate the wrongfulness of the conduct at the time of the offense.
(b) As used in this section, "mental disease or defect" means a severely abnormal mental condition that grossly and demonstrably impairs a person's perception, but the term does not include an abnormality manifested only by repeated unlawful or antisocial conduct.
As added by Acts 1976, P.L.148, SEC.1. Amended by Acts 1977, P.L.340, SEC.11; P.L.184-1984, SEC.1.