Mental illness or intellectual disability

(1) A person is not responsible for criminal conduct if at the time of the conduct, as a result of mental illness or intellectual disability, he or she lacks substantial capacity to appreciate the nature and quality of his or her conduct. (2) As used in this chapter, the term "mental illness or intellectual disability" does not include an abnormality manifested only by repeated criminal or otherwise antisocial conduct. (3) A defendant may prove mental illness or intellectual disability, as used in this section, in exculpation of criminal conduct.