Most people have probably heard of the insanity defense, in which a person who has committed a crime pleads “not guilty by reason of insanity” and claims that a mental illness caused them to act illegally. This might seem like an easy way to get out of being held responsible for breaking the law, especially in cases involving horrific crimes, such as the murder of multiple people. If a person can act crazy enough to fool the authorities into believing they were not in control of their actions, they can get off scot-free, right? In reality, the law is not so simple. The insanity defense will only apply in certain restricted situations, and some states do not recognize it at all. In most cases, a skilled forensic psychologist is needed to determine whether this type of defense is appropriate.
The modern discussion of the insanity defense began in 1843, when a man named Daniel M’Naghten attempted to assassinate the British Prime Minister because he believed the government official was personally conspiring against him. He was acquitted, and the court created a rule in which a jury could consider whether a person who committed a crime was suffering from a mental condition that caused them to be unable to understand the nature of their actions or to be unaware that what they were doing was wrong. This “M’Naghten rule” formed the basis of the insanity defense in both the United Kingdom and the United States.
Over the years, there have been a variety of refinements to the ways different states and the federal government approach the insanity defense, leading to the establishment of differing legal standards among the states. Some standards are less restrictive than the original M’Neaghten one. For example, the Model Penal Code, which was developed by the American Law Institute in 1972, states that a defendant may not be responsible for their actions if he did not have the “substantial capacity” to understand whether he (or she) were acting wrongfully or he was unable control his behavior and follow the law.
To be found insane under the more restrictive M’Neaghten standard, the defendant must show that, at the time of the offense, he was laboring under a mental illness that interfered with his ability to know what he did was wrong. This requirement of “knowing” is referred to as a cognitive element of the standard, which makes the defense very difficult to be used. The defendant must be suffering from a mental illness such that he did not have a rational understanding that his actions were morally or legally wrong. With the M’Neaghten standard, having been out of control of your behavior due to a mental illness is not enough to be found insane. A defendant must not have known his actions were wrong, with an active psychosis totally compromising his rationality. Consider a 26 years old defendant charged with residential burglary. The owners of the house came home and found him in their bedroom, pacing, holding a kitchen knife and rambling about how someone is trying to abduct him. Terrified, they called the police. A jury found him to have been psychotically irrational and out of touch with reality when he entered the dwelling. They concluded he was insane. On the other hand, I evaluated a psychotic defendant who strangled his mother to death, and found him sane (in California, where I practice, we have the M’Neaghten standard.) After an extensive forensic psychological evaluation, I concluded that he killed his mother out of anger, not because of his inability to know that what he was doing was wrong. He was mentally ill, but sane.
The popular imagination of the insanity defense is quite a bit different from how it actually applies in most criminal cases, and it is not the “get out of jail free card” that many believe it to be. It’s utilized in a very small fraction of criminal cases nationwide. With any specific legal standard, for the insanity defense to be successful, a person must typically have a history of severe mental illness that includes being hospitalized in the past, and multiple different professionals will usually need to agree on a diagnosis. Extensive interviewing and the use of psychological testing will have been employed to eliminate any type of symptom exaggeration or faking of psychosis.
If a person is found not guilty by reason of insanity, he may be able to avoid a prison sentence but they will usually be required to stay in a mental health institution, sometimes for longer than the time they would have been required to serve in prison. In some cases, a person must be able to demonstrate to expert evaluators and a judge that his sanity has been restored, and he is not a danger to the community before released. He then will be placed in a forensic-oriented half-way house, with close supervision for an extended period of time.