Diminished Capacity Law and Legal Definition

Diminished capacity is a legal defense used in some criminal cases to argue that the defendant was less mentally capable than a normal person of having the required mental state for the offense. The wrongful intent required for a criminal conviction is called mens rea. Diminished capacity does not amount to insanity, but is rather a condition that affects a defendant's ability to process information or to reason. It is also referred to as diminished mental capacity and partial responsibility.

Laws vary by state, but any or all mental disorders may satisfy the requirements of a diminished capacity defense. For example, in one case involving the "Twinkie" defense, a defendant claimed that a reaction to a high of intake of sugar affected his ability to reason.