This paper examines the U.S. doctrines that allow an offender's abnormal mental state to reduce murder to manslaughter. First, the modern doctrine of "extreme emotional disturbance," as in Model Penal Code Section 210.3(1)(b), mitigates to manslaughter what otherwise would be murder when the killing "is committed under the influence of extreme mental or emotional disturbance for which there is reasonable explanation or excuse." While most American jurisdictions are based upon the Mode Code, this is an area in which many states chose to retain their more narrow common law "provocation" mitigation. Second, the modern doctrine of "mental illness negating an offense element," as in Model Penal Code Section 4.02, allows a killing to be mitigated to manslaughter (or less) upon a showing that a mental disease or defect negated the culpable state of mind required for murder. This Model Code provision too has met with some resistance among the states, many of whom limit the use of mental illness evidence to negate an offense element. The paper discusses the state of the law in the various American jurisdictions, the reasons for the Model Penal Code shift from the common law, the possible reasons for resistance among the states to following that shift, an analysis of the mitigations under alternative distributive principles for punishment, concluding that only a desert principle supports the mitigations, and a discussion of the implications of this desert foundation for the proper formulation of the mitigations.
Robinson, Paul H., "Abnormal Mental State Mitigations of Murder – The U.S. Perspective" (2010). Faculty Scholarship at Penn Law. 325.