Insanity Defense

The insanity defense is an excuse for crime for those who, because of mental disorder, are not considered blameworthy. It is premised on the intuition that people with serious mental illness are so different from others that they cannot be held accountable for their criminal actions. Yet, many do not share in this intuition, and those who do have disagreed over the best formulation for capturing it.

The insanity defense has ancient roots. Greek and Hebrew civilizations recognized that serious mental illness should have mitigating impact and medieval English kings pardoned murderers who suffered from ‘‘madness.’’ The first modern test for insanity was devised in 1843 by the House of Lords in England. In M’Naghten’s case, the Lords announced that a person should be excused by reason of insanity if a ‘‘mental disease or defect’’ caused ‘‘a defect in reason that resulted in the inability to know the nature and quality’’ of the criminal act or caused the person to ‘‘not know that the act was wrong.’’

At about the same time, other courts were recognizing insanity claims based on a failure of the will rather than a lack of understanding. Thus, an American court held, in Parsons v. State, 81 Ala. 577, 596, 2 So. 854 (1887), that an insanity defense could also succeed if the person ‘‘has lost the power to choose between the right and wrong and to avoid doing the act in question, such that free agency is destroyed’’—a formulation that came to be called the ‘‘irresistible impulse’’ test for insanity. By the mid-twentieth century, most American jurisdictions had adopted the M’Naghten test or a combination of M’Naghten and the irresistible impulse test.

The M’Naghten and irresistible impulse tests were criticized on the ground that they required almost total impairment in terms of cognition (M’Naghten) or volition (irresistible impulse). In reaction to these complaints, in the 1950s American Law Institute (ALI) fashioned another test for insanity. This ‘‘ALI test’’ defines an insane person as one who, ‘‘as a result of mental disease or defect ... lacks substantial capacity either to appreciate the criminality [wrongfulness] of his conduct or to conform his conduct to the requirements of the law.’’ This formulation does not require complete cognitive or volitional incapacity, only ‘‘substantial’’ incapacity. Furthermore, it uses the word ‘‘appreciate’’ rather than M’Naghten’s ‘‘know,’’ a modification that, according to the ALI commentary, was meant to convey ‘‘a broader sense of understanding than simple cognition.’’ Well over half the states, as well as most federal courts, had adopted some version of the ALI test by the end of the 1970s.

The law of insanity changed considerably after John Hinckley’s insanity acquittal in 1982 on the charge of attempting to assassinate President Ronald Reagan. Within a short period after that case, several states had abolished the insanity defense, and many others had narrowed the types of mental disorders that could form the predicate for insanity, eliminated the ‘‘volitional prong’’ of the defense, changed the test language from ‘‘appreciate’’ back to ‘‘know,’’ shifted the burden of proving insanity to the defendant, or adopted some combination of these reforms. Representative of these efforts is the test promulgated by Congress in the Insanity Defense Reform Act of 1984, which provides that a person is insane if, ‘‘as a result of severe mental disease or defect,’’ he ‘‘was unable to appreciate the nature and quality or the wrongfulness of his acts.’’

Another post-Hinckley effort at undermining the effect of the insanity defense, adopted in about a dozen states, is the guilty but mentally ill (GBMI) verdict. This verdict is meant to provide juries with a compromise between an insanity finding and a straightforward guilty verdict. Empirical research indicates that the GBMI verdict has not reduced insanity acquittals, but rather merely provides jurors with another way of describing those who are normally found guilty. Furthermore, the verdict is seriously misleading to the extent that jurors or defense attorneys believe that it somehow mitigates sentence. In fact, persons found GBMI are supposed to and do receive the same sentence as if they had been found guilty, and several have been sentenced to death.

Approximately five states have abolished the insanity defense, although they still allow defendants to present psychiatric evidence that might prove the defendant did not intend the offense. This ‘‘mens rea’’ alternative has generally been upheld against constitutional attack, although one state court found it violated due process because it abolishes the (broader) insanity excuse (Finger v. State, 117 Nev. 548, 27 P.3d 66, 2001). Also of relevance here is the U.S. Supreme Court’s decision in Montana v. Egelhoff, 518 U.S. 37 (1996), which found that a state’s abolition of the intoxication defense did not violate due process primarily because that defense was ‘‘of recent vintage.’’ On this reasoning, the insanity defense, which has ancient origins, might be constitutionally mandated.

From the civil liberties perspective, whether and in what form the insanity defense should be retained is a difficult question to answer. Certainly some mentally ill people are relatively less blameworthy than other offenders, and the defense has historically been a useful method of escaping the death penalty. But in noncapital cases, confinement after an insanity acquittal can last as long as or longer than imprisonment for the same crime, and a broad insanity test might result in pervasive preventive detention of those with mental problems.

While treatment is supposedly provided people found insane, it should also be provided to those mentally ill people who end up in prison; using the insanity defense as a vehicle for obtaining treatment for the tens of thousands of mentally ill people who offend is inefficient and distracts attention away from the treatment needs of offenders who would not be found insane under any formulation of the defense. Some sort of insanity defense is worth keeping, however, as a recognition that some members of society are so impaired that a society that punished them would be a disgrace and also because cases that raise the issue forces people to confront what it means to be responsible for their actions.


References and Further Reading

  • Melton, Gary et al. Psychological Evaluations for the Courts: A Handbook for Mental Health Professionals and Lawyers, 2nd ed. New York: Guilford Press, 1997, chapter eight.
  • Perlin, Michael J. The Jurisprudence of the Insanity Defense. Durham, NC: Carolina Academic Press, 1994.

Cases and Statutes Cited

  • Finger v. State, 117 Nev. 548, 27 P.3d 66 (2001)
  • Montana v. Egelhoff, 518 U.S. 37 (1996)
  • Parsons v. State, 81 Ala. 577, 596, 2 So. 854 (1887)

See also Guilty but Mentally Ill


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