What is Not Guilty by Reason of Insanity?

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  • Written By: wiseGEEK Writer
  • Edited By: O. Wallace
  • Last Modified Date: 14 January 2020
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When a person has clearly committed a crime, there are some ways to avoid guilty verdicts, like by being declared not guilty by reason of insanity. This plea admits to the actions committed, but states the client could not judge or avoid the actions due to a mental condition. It’s also a determination a jury and a judge can make if it is proven the person was, and might still be, insane when a crime was committed. When people try to get this not guilty verdict, it is called the insanity defense, and ability to be declared not guilty this way requires significant proof by psychiatric expert witnesses.

It is much easier to prove an insanity defense when long-lasting and established mental health conditions exist. For instance, someone with schizophrenia, though most schizophrenics are law-abiding members of society, might be able to more easily claim that he is not guilty by reason of insanity. This might be particularly the case if the schizophrenic was not medicated or inadequately medicated at the time the crime was committed.


More difficult is attempting to prove temporary insanity, unless irrefutable evidence exists. For instance, a brain tumor pressing on the wrong area of the brain could cause rage or violent impulses that the person can’t help. This plea isn’t always as strong and may not convince a jury, but powerful motivation exists for the temporary insanity defense because it might lead to immediate release after trial. When someone uses a defense of insanity that isn’t temporary, he might be committed to a mental institution for months or years, until he can prove that he is sane.

Different regions define insanity or temporary insanity in varying ways. Usually, defendants who make this plea have to prove one of two things: they couldn’t help themselves in committing a crime because they were victim to an insanity condition, or alternately, they could not distinguish between right and wrong. This latter test is called the McNaughton (M’Naghten) rule.

There may be other distinctions within each jurisdiction about what types of insanity are considered. For example, addiction to mind-altering substances may not be insanity even if considered a mental health condition by the mental health community’s main diagnostic text, The Diagnostic and Statistical Manuals. People need to know when an insanity plea is justifiably made, based on laws in their area.

People who plead not guilty by reason of insanity can expect to undergo psychiatric examination by an expert witness who will testify in court as to whether or not he finds evidence of insanity. Many jurisdictions will support a defendant who makes this plea by funding an expert witness if the defendant cannot afford one. It’s often believed that people who are able to fund their own witness have better control over that testimony, but there can be excellent state psychiatrists who take their job seriously and do all they can to help a defendant.


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Post 2

Several years ago, in the late 1970s, there was a real insanity case I found fascinating. In the state of Ohio, a young man named Billy Milligan was accused of several charges of rape, to which he pleaded insanity- he in fact had multiple personality disorder, and was the first person with the disorder to try to plead it in court. He did get off, though to this day Milligan has struggled with the government over his treatment in facilities and with the believability of his story.

Post 1

In television and movies it can often be seen as a joke that murder defense lawyers and other attorneys will get their clients to plead insanity, but the reality is it is a very serious undertaking, whether the insanity is proven or not. People who are legally insane are often even more worried about and terrified of what they have done than people who might have understood the crime they were committing.

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