The McNaughton Rules: Not Guilty by Reason of Insanity

People sometimes get frustrated with our criminal court system when a person charged with a horrific crime enters a plea of not guilty by reason of insanity. There seems to be a common belief that this is a legal loophole that routinely allows guilty people to escape responsibility for their crimes.

Minnesota, like most states, largely follows what have become known as “The McNaughton Rules.” These rules were developed in England after Daniel McNaughton was found not guilty of murder by reason of insanity in 1843. Public outcry over the case prompted creation of the rules to clarify and restrict the future use of such defenses. Had the rules been in place at his trial, McNaughton would have been found guilty.

Under the McNaughton Rules, defendants are presumed to be sane and will not be excused from criminal liability except upon proof that at the time of committing the alleged crime they were suffering from a defect of reason, due to a mental illness or defect, so as not to know the nature of the criminal act, or that it was wrong.

A hypothetical example that I learned in law school illustrates this. A man is charged with murder for shooting someone in the head. Because of a serious mental illness or defect, the man did not know that he was shooting someone in the head. Instead, because of his distorted view of reality, he truly believed that he was target shooting at a watermelon.

In this example, the man rationally understood that he was shooting a gun at a specific target. However, he could not understand that the nature of the act was criminal because shooting watermelons is not illegal.

Similarly, as the term “wrong” under the McNaughton Rules refers to a general moral sense of right and wrong, the man’s conduct would also be excused because there is nothing inherently immoral in target shooting at watermelons.

Naturally, the law does not simply take a person’s word for a claim of a McNaughton defense. Experts, typically psychiatrists, are appointed to provide opinions to the court as to the person’s mental state. These opinions are based on a thorough review of all of the defendant’s medical and mental health records and upon in-depth mental examinations of the defendant by the experts.

Minnesota, like most jurisdictions, further requires defendants to prove the defense. Minnesota requires proof by the greater weight of the evidence. Some states, and Federal law, mandate proof by clear and convincing evidence - a higher standard.

It is very unusual for defendants to avoid criminal prosecution by raising a McNaughton defense. Additionally, even in those cases where the defense is successful, defendants do not go free. Instead, in Minnesota, the courts are required to order the person held for civil commitment proceedings as being mentally ill and dangerous. This means that while they will not be sent to prison for their crime, they will likely be held, perhaps for the rest of their life, in a locked mental institution.

Judge Galler is chambered in Washington County. If you have a general question about the law or courts for Judge Galler, send your question to the editor of this newspaper. Learn more about Judge Galler, or listen to a podcast of his columns at www.judgegreggaller.com.