If you’ve watched enough law movies and drama shows, chances are you have at some point seen a character plead insanity as a defense. According to a PBS article, less than 1 percent of county court cases involve the insanity defense, and that of those, only around one in four were successful. Despite this statistic, there are instances when this defense is successful. The first successful attempt at this defense was in 1843 when an Englishman shot and killed the secretary of the British Prime Minister, believing that the Prime Minister was conspiring against him. More recently, a teenager in Iowa was found not guilty of murder by reason of insanity in the death of his 5-year-old foster brother. So what exactly determines “insanity”?
First, the defendant must prove that he did not have control over his conduct similar to sleepwalking or being in a state of hypnosis. Secondly, the defendant does not have the ability to form criminal intent. They have no understanding of conduct that is “evil” or considered wrong by society’s standards. For example, if someone commits a crime and then tries to purposely mislead officers, they demonstrate an awareness that they did something wrong even if their behavior was mentally imbalanced. Due to these two factors in play, a defendant’s behavior is likely to be repeated again and again. As a result, there is no punishment or sentence that would rehabilitate the person. The only appropriate remedy is to treat their mental condition.
It is important to note that just with other areas of law, the insanity defense varies from state to state. Below are rules states use to define “insanity”: