How Does a Plea of Insanity Work?




With this being said, does that mean that more and more of our criminals can successfully plead Not Guilty by Reasons of Insanity (NGRI)? Bluntly put, no. A defense of insanity is essentially stating that due to mental illness a person was not able to decipher right from wrong, thus resulting in the occurrence of a crime. Many states take into account the presence of two fundamental elements to a crime, (1) mens rea (criminal intent), and (2) actus reas (criminal act) when determining NGRI. In order to assess if one can be convicted, the court must determine if a criminal act took place and if a criminal intention was present at the time of the crime. What does this mean? For example, if you have a heart attack while driving and accidently run someone over, you did not possess mens rea. For this reason, one would not be charged with let’s say, homicide. It is a similar thought process when evaluating someone for the presence of mens rea when committing a crime under a possible state of insanity. If a person that suffers from schizophrenia injuries another individual because his thoughts led him to believe that his life was in danger, this may potentially be viable grounds for a defense of insanity.



More often it is used effectively as a mitigating factor when negotiating a diminished level of criminal culpability. It is more beneficial to use this as a compromising tactic between defense and prosecution in order to lessen the potential sentence that one can possibly be facing. Diminished capacity (or sometimes referred to as diminished responsibility) is a partial defense in a criminal pursuit that has much lower standards than a plea of insanity and is widely more applicable. Partial defenses, similar to mitigating factors, are utilized in effort to minimize someone’s charges or sentence (e.g., reducing a murder charge to one of manslaughter).


In the case that a defense team does successfully receive a NGRI verdict, this does not mean that their client walks free. Traditionally, when one is found to be NGRI they still “do their time,” but it is served under the supervision of a mental hospital. Often times these “criminals” are sentenced to serving time in a mental institution or are required to receive psychiatric treatment/counseling.



Legal Information Institute. “The insanity defense and diminished capacity”. Legal Information Institute: Federal Law. Cornell University Law School. Retrieved 19 December 2011.

Lymburner, Jocelyn A. and Ronald Roesch. “The insanity defense: five years of research (1993-1997). ” International Journal of Law and Psychiatry 22(3-4): 213-240 (1999).

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