Insanity and Crime

The Insanity Defense

In most U.S. jurisdictions, the insanity defense has a cognitive aspect (unable to appreciate the wrongfulness of the conduct), and in a minority of jurisdictions, a volitional aspect (unable to conform his conduct to the requirements of law). Defendants are usually required to prove their insanity as an affirmative defense, either by a preponderance of evidence or, in some places, by clear and convincing evidence. In a few U.S. jurisdictions, the insanity defense has been abolished. In those states, defendants may introduce evidence to show only that their serious mental illness resulted in a lack of mens rea (guilty mind), a necessary element of a criminal case.

Although the insanity defense is seldom invoked (some studies claim that less than 1 percent of all defendants plead NGRI) and is even more rarely successful, the defense has generated centuries of debate and dissension, in part because it provides a complete defense for an accused who admits to committing the crime but seeks to be excused for such acts. In the unusual circumstance in which the insanity defense prevails, the state [Page 780]will confine the defendant in a mental institution following trial, often for a very long period.

The insanity defense has met with disfavor for centuries. In earlier centuries, insanity was often associated with demonic possession or viewed as a form of divine punishment. More recently, insanity has often been believed to be a ruse by which guilty people can avoid responsibility for their crimes. Although most citizens believe insanity exists and is a debilitating disease, many people are unwilling to believe that it can cause otherwise good people to commit heinous acts—as was evident when the jury convicted Andrea Yates after she drowned her children, claiming she was trying to save their souls. After that verdict was reversed on appeal, Yates was found NGRI in 2006. It is typical for juries to reject the insanity defense. In the unusual case in which the defense is successful, the public often reacts forcefully. When John Hinckley shot President Ronald Reagan and was found NGRI, Congress reacted quickly, enacting the Insanity Defense Reform Act of 1984, 18 U.S.C. §§ 17, 4241 (2000), which made it more difficult for defendants to successfully rely on the insanity defense in federal court. Many states have followed suit.

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