In any prosecution for an offense, it is an affirmative defense that
when the defendant engaged in the proscribed conduct, he lacked criminal
responsibility by reason of mental disease or defect. Such lack of
criminal responsibility means that at the time of such conduct, as a
result of mental disease or defect, he lacked substantial capacity to
know or appreciate either:
1. The nature and consequences of such conduct; or
2. That such conduct was wrong.