Insanity Defense Reform Act

The Insanity Defense Reform Act (IDRA), passed by Congress in 1984, imposed a uniform standard for legal insanity that applies in all federal trials in which the defense is raised; it also established the burden of proof in such cases.

Although criminal law is primarily the province of the individual states, the federal government has independent jurisdiction to prosecute criminal activity that concerns the federal government. In 1984, all the states and the federal criminal law had some version of the insanity defense, but the federal criminal code did not contain an insanity defense. Instead, each of the courts of appeal in the 11 federal judicial circuits had judicially adopted an insanity defense that applied in that circuit.

Ten of the 11 circuit courts of appeal had adopted the American Law Institute’s Model Penal Code (MPC) insanity defense, which permits acquittal by reason of insanity if

at the time of [the crime] as a result of mental disease or defect [the defendant] lacks substantial capacity either to appreciate the criminality (wrongfulness) of his conduct or to conform his conduct to the requirements of law. (MPC, Sec. 4.01(1))

One circuit still used the traditional M’Naghten test, which permitted acquittal if the defendant, as a result of mental disorder, did not know the nature and quality of his or her act or did not know that it was wrong.

In 1982, John W. Hinckley Jr. tried to assassinate President Ronald Reagan. Reagan survived, and Hinckley was charged with the federal crime of attempted murder of the President. Hinckley raised the defense of legal insanity. The case was tried in the federal district court in the District of Columbia, which had adopted the MPC test quoted above, which placed the burden of proof on the prosecution to prove beyond a reasonable doubt that the defendant was not legally insane. A jury found Hinckley not guilty by reason of insanity.

The unpopular verdict unleashed widespread criticism of the insanity defense in Congress and in many state legislatures, especially of the “loss-of-control” prong of the MPC test. There were many proposals to abolish the insanity defense, including from the Reagan Justice Department. Five state legislatures did abolish the insanity defense, although in one, the state Supreme Court held that abolition unconstitutional. The American Medical Association favored abolition, but the American Bar Association and the American Psychiatric Association opposed abolition on the grounds that it would lead to unfair results and that it was unnecessary to protect the public.

Many of the criticisms of the insanity defense were unfounded. For example, the defense has not let large numbers of defendants “beat the rap.” In fact, few defendants have succeeded with an insanity defense, and if those successful were not genuinely criminally responsible, then it would have been unjust to blame and punish them. Moreover, the arguments that all criminal defendants with severe mental disorder at the time of the crime were criminally responsible were morally and logically unpersuasive.

The Justice Department abandoned its call for abolition, and Congress decided to retain the insanity defense. The IDRA created a uniform insanity test applicable in all federal criminal trials in which the defense is raised. The test is as follows:

It is an affirmative defense to a prosecution under any Federal statute that, at the time of the commission of the acts constituting the offense, the defendant, as a result of a severe mental disease or defect, was unable to appreciate the nature and quality or the wrongfulness of his acts. Mental disease or defect does not otherwise constitute a defense.

The IDRA also placed the burden of proof on the defendant to prove by clear and convincing evidence that he or she was legally insane.

The legal insanity test created is similar to the traditional M’Naghten test and thus is narrower than the MPC test, which had been “blamed” for Hinckley’s acquittal. Criticisms of loss-of-control tests convinced lawmakers that they were unwise, and such a test was not included. Moreover, the federal test uses the phrase “unable to appreciate,” which suggests that this is a bright-line, all-or-none, question, whereas the apparently more forgiving MPC test points to “lack of substantial capacity.” Whether this wording difference makes a difference in practice is not clear.

Like M’Naghten, the federal test focuses on the defendant’s understanding of the nature and quality of the act or its wrongfulness. The test is apparently broader than M’Naghten, however, because it uses the defendant’s lack of “appreciation” rather than lack of “knowledge” as the operative criterion, and many think that appreciation includes an affective as well as a cognitive component. Whether this criterion is broader in practice is an open question. The test is also apparently narrower than M’Naghten because it explicitly requires that only a severe mental disease or defect will support a successful insanity defense.

Again, whether this restriction narrows the test in practice is an open question because few defendants suffering from less serious mental disorders were previously found not guilty by reason of insanity.

Perhaps the most important part of the IDRA was placing the burden of proof on the defendant, which makes it harder for the defendant to succeed. Placing the burden of proof on the defendant is constitutional because legal insanity is an affirmative defense rather than part of the definitional criteria for criminal offenses, and the Supreme Court has held that the prosecution must only prove the definitional criteria beyond a reasonable doubt. Jurisdictions are therefore free to impose the burden of proof for affirmative defenses on the defendant.

Later empirical research has confirmed that placing the burden of proof on the defendant is more successful in hindering insanity acquittals than narrowing the standard for legal insanity itself. This innovation is often criticized as unfair because it creates too much risk that a defendant who is genuinely legally insane will nonetheless by convicted, but it is constitutional, and Congress shows no inclination to change this rule.

The last sentence of the federal test quoted above has generally been interpreted by lower federal courts to mean that in federal criminal trials, evidence of mental disorder can also be used to negate the mental state required by the definition of most crimes, mens rea. Negation of mens rea using mental abnormality evidence is not considered an affirmative defense, so this interpretation is not inconsistent with the legislation. The Supreme Court held in Clark v. Arizona (2006) that jurisdictions are under no constitutional obligation to permit defendants to use evidence of mental disorder to negate mens rea, but most federal courts do permit this as a result of statutory interpretation of the IDRA.


  1. Clark v. Arizona, 548 U.S._126 S. Ct. 2709 (2006).
  2. Morse, S. J. (1985). Excusing the crazy: The insanity defense reconsidered. Southern California Law Review, 58, 777-836.
  3. Steadman, H. J., McGreevy, M. A., Morrissey, J., Callahan, L. A., Robbins, P. C., & Cirincione, C. (1993). Before and after Hinckley: Evaluating insanity defense reform. New York: Guilford Press.

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