What Is the Insanity Defense?

In the wake of the tragic mass shooting in Tucson, Arizona, speculation is growing that the accused shooter, Jared Lee Loughner, will invoke the insanity defense. Find out why this defense rarely works.

Adam Freedman
3-minute read

What Is the Legal Definition of “Insanity”?

Federal courts and most state courts follow the so-called M’Naghten rule for determining insanity.  Under this rule--devised by the British courts in 1843--a defendant may not be responsible for a crime if, because of a “disease of the mind” he did know the “nature of his act,” or “did not know that it was wrong.”  In other words, a person may have all sorts of nutty ideas, but unless he can show that his mental condition prevented him from understanding right and wrong, he won’t be judged criminally insane. 

Evidence  and the Insanity Defense

The federal insanity defense requires proof that the defendant did not understand the wrongness of his action at the time of the offense.

In 1984, following the successful use of the insanity defense by John Hinckley (who had tried to assassinate President Reagan), Congress passed legislation imposing a higher standard of proof on defendants, requiring “clear and convincing” evidence of insanity.  Congress also specified that the federal insanity defense requires proof that the defendant did not understand the wrongness of his action at the time of the offense, as distinct from some general inability to distinguish right from wrong.

How to Prove Insanity

To establish an insanity defense, Loughner will have to undergo a number of evaluations by psychiatrists and psychologists.  The evaluators will also be allowed to examine so-called collateral information.  That could include interviews with friends and former classmates.  It may also include analysis of the online musings that Loughner reportedly posted to various websites and YouTube.

As a result of TV shows and a few high profile cases--like the Hinckley case I mentioned--there’s a perception that lots of defendants get off on the insanity defense.  But in fact, the odds are against Loughner, or any other defendant who pleads insanity.  Consider the case of the “Unabomber” Ted Kaczynski, who was diagnosed as a paranoid schizophrenic and who sent letter bombs to a variety of people he perceived as enemies.  And yet, Kaczynski was still declared competent to stand trial and convicted on 10 criminal counts. 

Experts say that fewer than one percent of all felons claim insanity and, of those, only about 25% ultimately succeed in proving insanity.   And remember, even if a defendant “wins” on the insanity defense, generally the reward is a long, long stay in a mental institution.

Padded cell image courtesy of Shutterstock.


About the Author

Adam Freedman

Adam Freedman is a lawyer and a regular contributor to Point of Law and Ricochet. Freedman’s legal commentary has been featured in The New York Times, the Minneapolis Star-Tribune, and on Public Radio. He holds degrees from Yale, Oxford, and the University of Chicago. He is the author of The Naked Constitution (2012).

You May Also Like...