not guilty by reason of insanity | Definition

Doc's CJ Glossary by Adam J. McKee
Course: Introduction / Criminal Law

Not Guilty by Reason of Insanity is a plea that must be entered (in some jurisdictions) when the defendant is planning to use an insanity defense; some jurisdictions call this “guilty but mentally ill.”


Not Guilty by Reason of Insanity is a plea that can be used by a defendant in a criminal case who is planning to use an insanity defense. This plea is used to request a judgment of acquittal based on the fact that the defendant was not responsible for their actions at the time of the crime due to a mental illness or defect.

The Debate

The use of an insanity defense has been a controversial issue in criminal law for many years. Some argue that it is a necessary component of the legal system, as it provides a way for mentally ill defendants to be treated differently than those who are not mentally ill. Others argue that it is an easy way out for defendants who have committed heinous crimes.

Insanity Defense Criteria

In order to be successful in using an insanity defense, the defendant must meet certain criteria. First, the defendant must have a mental illness or defect that makes them unable to understand the nature and consequences of their actions at the time of the crime. Second, the defendant must have been unable to appreciate the wrongfulness of their actions.

Tests of Insanity

The M’Naghten Rule, which originated in an English court case in 1843, is one of the most common tests used to determine whether a defendant is legally insane. Under this rule, a defendant is considered legally insane if, at the time of the crime, they were suffering from a mental defect or disease that caused them not to understand the nature and quality of their actions or not to know that what they were doing was wrong.

Many jurisdictions have since modified or replaced the M’Naghten Rule with other tests for insanity. For example, the Model Penal Code test for insanity includes both cognitive and volitional impairment, requiring that the defendant not only lack the ability to understand the nature and quality of their actions but also be unable to conform their conduct to the requirements of the law.

In some jurisdictions, a plea of “Not Guilty by Reason of Insanity” is not an automatic acquittal. Instead, the defendant may be found “guilty but mentally ill.” This means that the defendant is held criminally responsible for their actions but will be provided with appropriate mental health treatment while in custody.

It is worth noting that the use of an insanity defense can be a difficult strategy for a defendant. If successful, it may result in a verdict of not guilty, but the defendant may still be committed to a mental health facility for treatment. Additionally, even if the defense is successful, the stigma of being accused of a crime can be difficult to overcome.

Conclusion

In conclusion, Not Guilty by Reason of Insanity is a plea that can be used by a defendant who is planning to use an insanity defense. While this defense can be a difficult strategy, it may be necessary for those who are unable to understand the nature and consequences of their actions due to mental illness or defect. The use of the M’Naghten Rule and other tests for insanity can help determine whether a defendant is legally insane and eligible for this defense.

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Last Modified: 04/10/2023

 

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