Irresistible-impulse test refers to a test for insanity. This test determines that a person is not guilty of a criminal act because the person’s insanity prevented him/her from controlling the criminal activity. Irresistible-impulse test is also known as impulse test or control test. The test also determines the capacity of a person to distinguish between right and wrong. Irresistible-impulse test involves not only questions of scientific knowledge but also questions of basic policy as to the extent to which that knowledge should determine criminal responsibility.[Hashfield v. State, 247 Ind. 95, 101 (Ind. 1965)]
Irresistible-impulse is a defense by excuse. Moreover, the defense of irresistible-impulse can only be pleaded under the defense of diminished responsibility.