An irresistible impulse is an action that someone takes without the ability to control whether he or she is taking that action. In legal situations, this term is often used to refer to a form of defense in which a person claims he or she is not guilty due to an inability to control his or her actions. This type of defense is not recognized in all jurisdictions, though many areas do accept it in some situations. An irresistible impulse is often scrutinized under a test commonly referred to as the “Policeman at the Elbow” test to demonstrate whether someone could control the actions being taken.
Generally considered a specific form of diminished capacity defense, an irresistible impulse is a defense by excuse, rather than a defense of inaction. When someone claims that he or she was under the control of an irresistible impulse, then he or she admits to having performed an action that is being charged as a criminal offense. The defense, however, is that the action that was performed was done without control and therefore is not the responsibility of the defendant. Someone who attacks a person who may have harmed him or her in the past, but not in a situation of self-defense, may claim that he or she was unable to control his or her actions at the time of the attack due to past trauma.
There are a number of countries in which a defendant can use an irresistible impulse as a defense, such as England and certain states in the US. Other areas allow for certain cases to be argued with a defense of irresistible impulse, though only under specific conditions. This limitation often allows for such a defense to be used as long as it would cause a conviction of a lesser charge, such as a felony murder case that is defended through diminished capacity that results in a misdemeanor conviction.
In some areas, successful use of an irresistible impulse defense can result in mandatory treatment at a psychiatric facility, rather than release or imprisonment in a correctional institution. The test to determine whether someone was under an irresistible impulse is often referred to as the “Policeman at the Elbow” test. While various questions can be asked during this test, essentially the purpose of the test is to determine whether or not the person would have committed the action if a police officer was standing next to him or her at the time. This does not evaluate a sense of whether the defendant understands right and wrong, but whether the defendant could control his or her actions at the time.