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The 'Model Penal Code' Test for Legal Insanity

Created by FindLaw's team of legal writers and editors.

A criminal defendant who is found legally insane (or "not guilty by reason of insanity") cannot be held accountable for crimes resulting from the condition. Prosecutors are required to show a defendant's willful intent in order to prove guilt for most criminal charges. If a criminal defendant is ruled legally insane, there can be no willful intent.

There are several legal tests used by State courts to determine whether someone was insane at the time of the incident. These insanity defenses include the M'Naghten Rule; the Irresistible Impulse Test; the Durham Rule; and the Model Penal Code test.

This article focuses on the Model Penal Code test, which is the more modern standard used to determine legal insanity.

Model Penal Code Test for Legal Insanity: History

The Model Penal Code test ("MPC test"), was widely adopted in the 1970s since it allowed more flexibility than other tests at the time. However, it fell out of favor when John Hinckley, Jr. was found not guilty by reason of insanity (based on the MPC test) for his attempted assassination of President Ronald Reagan in 1981.

Hinckley grew up in a middle-class home and although had had a troubled background, did not exhibit overt signs of mental illness. However, at his trial his obsession with the movie Taxi Driver and one of its stars, Jodie Foster, was on full display. In the movie Taxi Driver, the lead character, Travis Bickle, was a lonely and depressed taxi driver who plots a political assassination and the rescue of a young prostitute. Evidence was presented that Hinckley identified with Travis Bickle and tried to emulate him which led Hinckley to try to assassinate President Regan in an attempt to impress Jodie Foster.

The jury found Hinckley had a mental defect that made him not guilty by reason of insanity, but the nation exploded with outrage over the verdict. Within a month after the verdict, Congress held hearings about the insanity defense. Congress followed up with legislation to shift the burden from the prosecution to the defense as to proof of insanity and to narrow the definition of insane. The States followed suit and changed state law to conform with the Congressional findings. Today, most states place the burden on the defense to prove insanity, some states have a finding of guilty but insane, and Utah abolished the defense altogether.

Model Penal Code Test for Legal Insanity: Basics

Under the MPC test a criminal defendant is not guilty by reason of insanity if he is diagnosed with a relevant mental defect (for example, severe mental retardation or schizophrenia disorder) and at the time of the incident was unable to either:

  1. Appreciate the criminality of his conduct; or
  2. Conform his conduct to the requirements of the law

Therefore, using the MPC test, a legally insane individual must have been diagnosed with a mental defect (typically by a court-appointed mental health professional) and either did not know right from wrong or lacked the ability to control an impulse that led to the incident.

Other Tests for Legal Insanity

The Model Penal Code test is much broader than the M'Naghten Rule and the Irresistible Impulse Test. The M'Naghten rule requires the inability to understand right from wrong under. The Irresistible Impulse Test requires the inability to control an impulse even though the defendant knows that it is wrong.

However, the MPC rule asks whether defendants are able to fully understand the criminality of their conduct or able to conform their conduct to the law, combining these two elements. The MPC rule also requires that the mental disease or defect be diagnosed by a licensed mental health professional. In this way, it incorporates the main element required by the Durham Rule.

Do You Have a Defense Under the Model Penal Code Test? Talk to a Lawyer Today

Under any test used, an insanity defense is going to require pre-trial motions and specific factual findings regarding medical conditions. A qualified criminal defense attorney can walk you through this process and let you know whether this is a workable defense. If you have more questions about insanity defenses or need professional representation, get in touch with an experienced, local criminal defense attorney today.

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