Diminished Capacity

Diminished capacity refers to two distinct doctrines. The first, known as the mens rea variant, refers to the use of evidence of mental abnormality to negate a mens rea—a mental state such as intent, required by the definition of the crime charged (the mens rea variant). The second, known as the partial responsibility variant, refers to the use of mental abnormality evidence to establish some type of partial affirmative defense of excuse. Courts have used various other terms, such as diminished responsibility, to refer to one or both of these distinct doctrines, but the term used is unimportant. Confusion arises, however, when the two types of doctrine are not clearly distinguished. Neither entails the other, and distinct legal and policy concerns apply to each.