Hg org Legal Resources Revised 2017 Top of Form Bottom of Form The insanity defense is one of the most controversial defenses. Additionally, it has one of the lowest success rates among all criminal defenses

When Is a Person Legally Insane?

 Provided by HG.org Legal Resources Revised 2017

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The insanity defense is one of the most controversial defenses. Additionally, it has one of the lowest success rates among all criminal defenses. Knowing about the insanity defense and when this defense may apply has the potential to help a criminal defendant who may be able to assert this defense.
Definition of Insanity

The definition of legally insane is a legal determination, not a psychological one. However, a psychological analysis plays into this. At times, a person may be considered psychotic but still not meet the legal definition of being insane. The legal definition of insanity varies by jurisdiction. Different states use different standards to determine if a person is legally insane. 

General Guidelines

The United States legal tradition is that if a person is unaware of what they are doing or that what they are doing is morally wrong, that person should not be held legally responsible for their behavior. For many crimes, a specific mens rea (the intention or knowledge of wrong-doing) must be proven. This is a certain mental state as determined by the statute. One court ruling is that a person should only be determined to be guilty and receive sentencing if he or she had the free will to commit the crime and the intent to cause harm. 

Standard Used to Determine If a Person Is Legally Insane
Different states use different tests, such as: 

M’Naghten Test
Most states use what is called the M’Naghten test to determine if someone is legally insane. It is a cognitive test that assesses the thought processes and perceptions that the defendant had at the time that he or she committed the crime. According to this test, a person is considered legally insane if, at the time of the offense, he or she suffered from a defect of reason from a disease of the mind. Due to this mental disease, the defendant did not know that what he or she was doing was illegal or wrong and did not know the consequences that might flow from the act.

Some states that use the M’Naghten test have diverged somewhat from this criterial. For example, in Arizona, the law was revised so that the phrase “knowing the nature and quality of the act” was omitted. The United States Supreme Court approved this modification. 

Brawner Rule
Another popular test is the ALI standard or Brawner Rule. This test states a person is not responsible for what would otherwise be considered criminal conduct if he or she lacked substantial capacity to appreciate the criminality of the conduct because of a mental disease or defect. The rule excludes mental illnesses that are due to the defendant committing repeated criminal acts throughout his or her life. About 20 states use this standard. 

Durham Test
New Hampshire is the only state that uses the Durham Test. This test only requires the showing that the criminal act was a product of a mental disease or impairment. In this state, it is much easier to meet the definition of legal insanity due to not having to prove as much. Many practitioners interpret this test to mean that any mental illness diagnosis can be used to meet the mental impairment qualification. 

Irresistible Impulse Test

This test is sometimes used in conjunction with the M’Naghten test. Under this test, the defendant must have a defect of the mind that makes it impossible for him to control his actions. It is not sufficient to meet this test if someone is overcome by jealously, anger, or other strong emotions…such passions could reduce a killing from murder to voluntary manslaughter.

Model Penal Code Test

Another test for insanity is set out by the Model Penal Code. Under this test, a person is considered insane if, because of a mental disease or defect, the person did not have the capacity to:

1. 
   Understand the criminality of wrongfulness for his conduct, or
   
2. 
   To conform his conduct to the law.
   

This is sometimes called the “policeman at the elbow test.” In other words, if the person would have committed the act even if there had been a police officer at her elbow watching her, she is considered unable to have understood the wrongfulness of her conduct or to conform her conduct to the law.
A defendant’s sanity may be proven by either medical professionals or by lay (non-expert) witnesses. Lay witnesses may testify about the defendant’s behavior around the time of the crime to help the jury determine whether the defendant was sane or insane at the time of the crime.
Burden of Proof
In a criminal case, the prosecution has the burden of proof of showing that the defendant committed each element of the crime by proof beyond a reasonable doubt. If the prosecution fails to meet this burden, the defendant should not be convicted. However, the burden of proof in a criminal case shifts to the defendant if he or she asserts the insanity defense. This means that the defendant has the duty to show that he or she is legally insane. This applies to federal cases as well as most state cases.