The MPC Test, or Model Penal Code Test, is the current method of determining if a plea of insanity meets the legal requirements to find an individual not guilty by reason of insanity. The MPC Test came from a text of the same name published by the American Law Institute in 1962.
The MPC Test established the idea of a reasonable person as the standard by which a plea of insanity could be examined.
The reasonable person test is a legal fiction, defined as an entity that (1) is always in control of its actions, (2) never consumes any item which would impair its ability to make a sound judgment, and (3) always contemplates the potential consequences that may arise from their actions before taking any action.
The reasonable person standard represents the bare minimum set of criteria that a given person must satisfy to be considered sane and reasonable. If the actions of the defendant in a given case do not satisfy the reasonable person standard, then that defendant has grounds for establishing an insanity defense.
The reasonable person standard does not make any allowance for the mentally ill. This is one of the main criticisms leveled against it. It is not meant to measure the actions of a person entering a plea of insanity against the actions of the normal person. This is an important distinction to make because it requires rationality, not actions that would be undertaken by the majority of people.
The MPC definition of insanity draws elements from the M'Naghten Rule, the Irresistible Impulse Test, and the Durham Rule. It allows a plea of insanity under M'Naghten's standard by recognizing the ability or inability of the defendant to determine if their actions are legally right or wrong.
The Irresistible Impulse Test is incorporated into the MPC Test by allowing not guilty pleas of insanity in the event the individual was unable to control him or herself. The Durham Test added allowance for a plea of insanity if there was a demonstrable history of mental illness or disease on the part of the defendant.
Such defendants attempting to enter a plea of insanity are required to provide proof of a mental diagnosis affirming their mental illness.
Most states adopted statutes allowing defenses to claim a reduction of charges by reason of insanity after the MPC established the standards in 1982, when the American Law Institute revised the MPC. Although the MPC was once the standard by which the Federal Government allowed not guilty pleas by reason of insanity, this is no longer the case. Currently, most states no longer adhere to the standards of insanity laid out in the MPC.
