In television and movies, the insanity defense is quite common and often successful. Additionally, many high-profile cases have used the defense with varying degrees of success. Due to this media saturation, it is easy to assume that the insanity defense is in regular use in the American court system. However, this is not actually the case. Provided here is a brief overview of the history and current status of the insanity defense.

The M’Naghten Case

Today’s insanity defense is actually rooted in 19th century British law. Daniel M’Naghten was a woodworker who believed in an elaborate conspiracy theory that involved both the pope and the Prime Minister, Robert Peel. M’Naghten went to 10 Downing Street to ambush Peel, but mistakenly killed Peel’s secretary. He was found delusional by multiple psychiatrists, and was ruled not guilty by reason of insanity.

News of the verdict led to a public outcry. Amid public pressure, a panel of judges developed the M’Naghten rule. This rule states that defendants may be found not guilty by reason of insanity only if they suffer from a defect of reason that prevents them from understanding what they were doing or that it was wrong. Often referred to as the right-wrong test, this rule has been a part of the insanity defense in both the British and American systems for over 150 years.

State Laws

Just over half of the states in the United States currently use some version of the M’Naghten rule. Each state has its own wording and case law precedent for its application. Some states have modified the law to include wording to the effect that the defendant must be acting on an irresistible impulse that is caused by his or her condition.

Several states now use a different standard that was set forth by the American Law Institute in 1962. This version of the insanity defense is less restrictive, using language to the effect that the defendant may be found not guilty if at the time of crime, his or her condition led to a lack of substantial capacity to understand the wrongfulness of the action or to conform his or her behavior to the law.

The Hinckley Case

On March 30, 1981, John Hinckley attempted to assassinate then-President Ronald Reagan. Several people, including Reagan, were seriously wounded. His stated reasoning was an attempt to impress movie star Jodie Foster, with whom Hinckley was obsessed.

Hinckley’s case went to trial in 1982, where he faced 13 separate charges. He was soon found not guilty by reason of insanity. He was committed to St. Elizabeth’s Hospital in Washington, DC, where he remains at this time.

Public shock and outrage at the verdict led to a massive rewriting of insanity defense laws. Some states dropped the insanity defense altogether. Others tightened both the requirements for claiming the defense and the consequences of such a verdict.

After the Trial

If a defendant is found not guilty by reason of insanity, he or she is generally committed to a psychiatric institution. The defendant remains in the psychiatric facility until he or she is found to be no longer dangerous. In practice, many people remain in psychiatric custody for much longer than the prison sentence would have been. Additionally, those who have taken this route may remain under the guidance of psychiatric experts even after release from the hospital.

Each state sets its own guidelines in regard to commitment of the criminally ill. Some states require that normal commitment procedures be followed, while others have special guidelines for those who have committed crimes. Additionally, each state sets its guidelines on release procedures. Depending on the state, release orders may be given by a judge, a hospital administrator or even a specially appointed board.

In some states, defendants may be found guilty but mentally ill. In this scenario, the defendant is sentenced as normal. However, he or she is initially sent to a psychiatric facility. If the defendant is deemed “cured” or “no longer dangerous” before the length of the sentence is complete, he or she is then transferred to a prison facility to serve the remaining sentence. Many advocates feel that this option takes pressure off the court system to determine whether or not a specific defendant is insane enough to be worthy of a not guilty judgment. At the same time, the option allows those who are truly mentally ill to receive the psychiatric care that they require without subjecting them to prison life prematurely.

Critics of the guilty but mentally ill provision feel that those who are legitimately mentally ill may not get the post-hospital care that they require. Mental health services are notoriously difficult to receive in prison, and some feel that the prison system may undo some of the healing that took place in the hospital.

Rarity of the Insanity Defense

Despite film and television references that make it appear common, studies show that only about one percent of defendants attempt to invoke the insanity defense. Of these, only approximately one quarter are successful.

Contrary to popular belief, the insanity defense is not only invoked in murder trials. Any form of crime could conceivably invoke the insanity defense. A particularly high-profile recent case was that of Lorena Bobbitt, who successfully invoked the defense. She was released from psychiatric custody after three months.

Many other high-profile cases featured a failed attempt at using the defense. David Berkowitz, aka the “Son of Sam,” and Jeffrey Dahmer both tried to invoke the insanity defense, but were both found guilty of their crimes.

The Bottom Line

The insanity defense has undergone many changes since 19th century British law. It is often misunderstood, seen as a commonly used “get out of jail free” card. However, the truth is that the defense is rarely invoked, and rarely successful. Those who do successfully use the defense often face a term of psychiatric commitment that may be even longer than the comparable prison sentence.