Legal Definitions - insanity plea

An insanity plea is a legal strategy used in criminal cases where a defendant claims they should not be held criminally responsible for their actions because, at the time the alleged crime was committed, they were suffering from a severe mental disease or defect. This condition must have prevented them from understanding the nature of their actions or from knowing that what they were doing was wrong.

The purpose of an insanity plea is not to deny that the defendant committed the act, but rather to argue that they lacked the necessary mental state (often called "mens rea" or guilty mind) to be held accountable under criminal law. If successful, the defendant is typically found "not guilty by reason of insanity" and may be committed to a mental health facility for treatment rather than serving a prison sentence.

• Example 1: A person with no prior history of violence experiences a sudden and severe psychotic break, believing they are receiving direct commands from a supernatural entity to harm a stranger. They act on these delusions and commit an assault. Their defense attorney might enter an insanity plea, arguing that the individual's severe mental illness at the time rendered them incapable of understanding that their actions were illegal or morally wrong.

  This illustrates an insanity plea because the defense claims the defendant's actions were a direct result of a severe mental disease (psychosis) that prevented them from comprehending the wrongfulness of their conduct.

• Example 2: An individual with a long-standing diagnosis of paranoid schizophrenia, who has been off their prescribed medication for several months, develops an elaborate delusion that their neighbor is actively plotting to poison them and their family. Acting on this delusion, they break into the neighbor's home to "disarm" what they perceive as a threat. An insanity plea would contend that their severe mental illness and resulting delusions prevented them from forming the criminal intent necessary for burglary, as they genuinely believed they were acting in self-defense against a perceived threat.

  This example demonstrates an insanity plea by showing how a severe, chronic mental illness can lead a person to commit an act while genuinely believing their actions are justified or necessary due to their delusional state, thus lacking criminal culpability.

• Example 3: A person suffering from severe bipolar disorder experiences an extreme manic episode, during which they engage in highly reckless and destructive behavior, including significant property damage to a public building. During this episode, they genuinely believe they are invincible, above the law, and that their actions have no real negative consequences, completely losing touch with reality. An insanity plea would argue that their severe mental illness, specifically the acute manic episode, so profoundly impaired their judgment and understanding of right and wrong that they could not be held criminally responsible for the damage.

  This illustrates an insanity plea by highlighting how a severe mental health crisis, like an extreme manic episode, can so drastically alter a person's perception of reality and consequences that they are deemed unable to form the mental state required for criminal responsibility.