By Popular Delusions, a blog by Honors Intro to Psychology students
Are These Criminals Insane! | Popular Delusions (wordpress.com)
Have you ever watched the court show Judge Judy, or perhaps CSI or Law and Order? These shows are inspired by real-life crimes, but they have a Hollywood twist to create an entertaining story. One commonality between reality court shows is the exaggerated use of the insanity defense. Humans are naturally more likely to remember the successful instances of using the insanity defense rather than the unsuccessful attempts. This has led to the American belief that a large proportion of criminals successfully use the insanity defense, although that is not the case.
First, let’s make sure we all understand exactly what the insanity defense is. In some cases, there is hard evidence against the defendant that will almost certainly result in a guilty verdict. In these instances, the defendant may admit to their actions but plead not guilty due to insanity. The insanity defense follows some variant of the M’Naughten rule, which states that “defendants must have either not known what they were doing at the time of the act or not known that what they were doing was wrong”(Lilienfeld et al., 2010. p. 218).
One popular case that shows the use of the insanity defense is the Jefferey Dahmer trial. Dahmer began pleading not guilty to the 15 charges of murder, but the evidence was too strong for him to win the case. Soon after, Dahmer admitted to committing the murders but claimed that he could not be held accountable because he was legally insane. Due to this change, a large part of the trial consisted of testimonies from psychiatric professionals, most of whom believed Dahmer had a mental illness. Nonetheless, the jury concluded that Dahmer was not insane because he was in control of his behavior (Kettler, 2021). In this trial, Dahmer had several pieces of testimonial evidence showing he was insane, but the jury’s decision proved how difficult it can be to successfully use the insanity defense.
Do you still believe that the insanity defense is an easy out for criminals? Well, the statistics should change your mind. Studies revealed that the average person believes the insanity defense is used in 37% of trials and has a success rate of 44% (Lilienfeld et al., 2010).
Although most Americans share a similar viewpoint on the insanity defense, they are wildly inaccurate. “Data indicates that this defense is raised in less than 1% of criminal trials and that it’s successful only about 25% of the time” (Lilienfeld et al., 2010). These results can be explained by the availability heuristic, which is a popular term used among psychologists. When a trial is successful in using the insanity defense, it is often controversial and circulates through the media. As a result, it is easily available in people’s memory and leads Americans to believe that the defense is used more often than it actually is.
So next time you hear someone bring up the insanity defense, just know that it is more uncommon and unsuccessful than what it is made out to be.
References
Kettler, Sara. “What Was Jeffrey Dahmer’s Murder Trial Like?” Aetv.Com, 28 Oct. 2021, www.aetv.com/real-crime/dahmer-trial. Accessed 18 Oct. 2023.
Lilienfeld, S. O., Lynn, S. J., Ruscio, J., & Beyerstein, B. L. (2010). 50 Great Myths of Popular Psychology: Shattering Widespread Misconceptions about Human Behavior. Blackwell Publishing. https://ci.nii.ac.jp/ncid/BA91476696
Mitrokostas, Sophia. “7 Things Crime Shows Always Get Wrong, according to Law Enforcement Professionals.” Insider, www.insider.com/things-crime-shows-get-wrong-about-real-life-2019-3#although-popular-in-tv-courtrooms-the-insanity-defense-is-rarely-used-in-real-life-criminal-cases-2.
