A person is criminally not responsible for his actions if at the time of doing it by reason of unsoundness of mind, in incapable of knowing the nature of the act or that he is doing what is either wrong or contrary to the law.

Mc Naughten rule states that person is criminally not responsible for his actions if he is unsound by mind and incapable of knowing the nature of the act. Curren's rule states the person do not have any capacity to regulate the conduct to the requirements of the law as a result of mental disease. Durham's rule is person's unlawful act is the product of mental disease or mental defect. Irresistsble impulse test states that even if the person knows that the nature and quality of the act and he Is wrong because the free agency of his will has been destroyed by mental disease.