What Is… Insanity in the Criminal Justice System

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In this series, I dig a little deeper into the meaning of psychological terms.  This week’s term is insanity.

Wikipedia is always the first place I turn for this series, but I think this particular Wikipedia page could use some work. It opens with: “Insanity, madness, and craziness are terms that describe a spectrum of individual and group behaviors that are characterized by certain abnormal mental or behavioral patterns.” That particular spectrum sounds like a load of crap to me.

Historical uses

In most contexts, insanity is a very old-school term.  In 1840, the term “idiocy/insanity” was a category used in the United States census.  Over time, that classification grew to include what was then known as melancholia, paresis (physical weakness), mania, monomania (obsession with a particular thing), dipsomania (excessive water consumption to the point of intoxication), dementia, and epilepsy. In 1917, a predecessor to the DSM was published, the Statistical Manual for the Use of Institutions for the Insane. As far as I can tell, insanity was never included as a diagnosis in the DSM.

Insane in the eyes of the law

Although insanity is no longer a medical term, it’s used in a legal context to describe whether an individual was of sufficiently sound mind to be able to differentiate right from wrong at the time of committing a criminal act. Timing is very important, as simply having a mental illness isn’t sufficient to be considered insane in a court of law. Even if someone was ill at the time of the crime, if they were still able to distinguish right from wrong, then they wouldn’t be considered insane. No particular diagnosis is necessary to be deemed insane, although it often arises from psychotic symptoms.

United States

How the courts deal with this depends on the jurisdiction. In the United States, an insanity defense is presented by the defendant’s counsel. Forensic psychiatric evaluations are done to support this defense. In the end, the jury decides whether or not to accept that the accused was insane.

According to Wikipedia, in the U.S. it’s more common for the defense counsel to argue diminished responsibility or diminished capacity, which involves a lessening of responsibility due to a temporary mental state. There are variations from state to state in terms of availability of this defense, type of evidence required, burden of proof, and standard of proof.

A particular variant of this defense, called “settled insanity,” is available in certain states. This refers to a permanent mental impairment brought about by long-term substance abuse. While voluntary intoxication is not permitted as a defense, settled insanity is considered different because it takes away the capacity for criminal elements like malice aforethought (premeditation).

Other countries

In Canada, a finding of “not criminally responsible” by reason of mental disorder is used when a mental disorder caused an individual to be unable to appreciate the nature of the act and understand that it was wrong at the time of committing the offense. If there is information to suggest the accused is not criminally responsible, the judge can order a forensic psychiatric evaluation. This is done over a period of time at a forensic psychiatric hospital. A judge then makes the final determination, and the standard of proof is based on a balance of probabilities.

In Nordic countries, it is the court’s responsibility to evaluate the accused’s mental state, even if the defense doesn’t make an insanity argument.

The stigma connection?

What I find so interesting about insanity is that the average person probably knows little about how it’s used and what it actually means. It makes me wonder if the lack of awareness around this serves to perpetuate stigma. There are already far too many ignorant assumptions connecting mental illness and violence. Does it help anything for people to be throwing around terms like “criminally insane”, which gets 3.8 million hits on Google? Even if it weren’t horrendously stigmatizing, “criminally” is redundant given that insanity only has meaning in the justice system.

I think insanity is an old-fashioned term that’s better off left in the past, along with lunatic, and various others. “Not criminally responsible” as used in Canada seems much more appropriate. And criminally insane certain belongs in the rubbish bin of history.


The Psychology Corner: Insights into psychology and psychological tests

The Psychology Corner has an overview of terms covered in the What Is… series, along with a collection of scientifically validated psychological tests.

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Ashley L. Peterson


Ashley is a former mental health nurse and pharmacist and the author of four books.

6 thoughts on “What Is… Insanity in the Criminal Justice System”

  1. I think these days I only really see “criminally insane” in comics like Batman where the actions of villains like the Joker are put down to being “criminally insane”.

  2. We say someone ‘lacked mental capacity’ in the UK.

    Although I like Hunter S Thompson’s quote to the effect of ‘the only difference between the sane and the insane is that the sane have the power to lock up the insane’

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