Insanity Defense in U.S. Law

The Insanity Defense: A Deep Dive into U.S. Legal Rulings

The concept of the insanity defense is an integral part of the U.S. criminal justice system, rooted in the idea that a person cannot be held criminally responsible for an act if they lack the mental capacity to understand its wrongfulness or control their actions. While often portrayed in popular culture as a “get out of jail free” card, it is a complex and rarely used legal plea. This defense serves as an affirmative defense, meaning the defendant acknowledges committing the act but asserts a lack of culpability due to a severe mental disease or defect at the time of the offense.

Historically, the legal system has long recognized the need to differentiate between individuals who are criminally responsible for their actions and those who are not. The evolution of the insanity defense in the United States has been shaped by a series of landmark cases and legal standards. From the earliest “wild beast” tests to modern standards, the legal definition of insanity is distinct from a clinical or medical diagnosis of a mental disorder. A person can be medically insane but still be held legally culpable for a crime.

Historical Foundations and Landmark Rules

The modern understanding of the insanity defense is largely based on a few key historical standards:

• The M’Naghten Rule: Originating in 1843 in England, the M’Naghten rule became the standard for insanity in the U.S. for over a century. Under this cognitive test, a defendant is not criminally responsible if, at the time of the offense, they were suffering from a mental disease that prevented them from knowing the nature and quality of their act, or that the act was wrong. Nearly half of U.S. states still use a version of this rule.
• The “Irresistible Impulse” Test: Some jurisdictions supplemented the M’Naghten rule with this test to address situations where a person could distinguish right from wrong but was unable to control their actions due to a mental disease. This is sometimes referred to as the “policeman at the elbow” test.
• The American Law Institute (ALI) Model Penal Code Test: Introduced in 1962, this test was intended to soften the M’Naghten standard. It states that a defendant is not criminally responsible if, as a result of a mental disease or defect, they lacked the “substantial capacity” to either appreciate the criminality of their conduct or to conform their conduct to the requirements of the law.

The Insanity Defense Reform Act of 1984

A significant shift in federal law occurred with the passage of the Insanity Defense Reform Act of 1984, which was a direct result of public outcry following the acquittal of John Hinckley Jr. for the attempted assassination of President Ronald Reagan. This act made several key changes to federal insanity law, including:

• Significantly modified the standard for insanity by adopting a stricter version of the M’Naghten rule, requiring a “severe mental disease or defect”.
• Placed the burden of proof on the defendant to establish the defense by “clear and convincing evidence”. This is a higher standard than the “preponderance of the evidence” often used in civil cases.
• Limited the scope of expert testimony on ultimate legal issues.

The U.S. Supreme Court has also weighed in on the insanity defense, affirming that states have the freedom to abandon it altogether, as seen in the 2020 ruling of Kahler v. Kansas.

Modern Procedural Aspects

Procedurally, a defendant who intends to present an insanity defense must file a notice with the court, which often leads to court-appointed experts—such as a legal expert or a medical expert—examining the defendant to assess their mental state at the time of the offense. The findings of these examinations are compiled into a report for the court and both the prosecution and defense.

If a defendant is found not guilty by reason of insanity (NGRI), they are typically not released. Instead, they are often committed to a secure psychiatric facility for treatment, with release depending on their recovery and a determination that they no longer pose a danger to themselves or others.

Summary of Key Takeaways

1. The insanity defense is an affirmative defense that requires the defendant to prove, by “clear and convincing evidence” in federal cases, that they lacked criminal responsibility due to a severe mental disease or defect.
2. The legal concept of insanity is separate from a medical diagnosis and is primarily judged by a defendant’s inability to appreciate the wrongfulness of their actions or to conform their conduct to the law.
3. Landmark standards like the M’Naghten rule and the ALI Model Penal Code have shaped the application of this defense across different U.S. jurisdictions.
4. The Insanity Defense Reform Act of 1984 made it more difficult to successfully use the defense at the federal level by raising the burden of proof and limiting the standard.

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FAQ about the Insanity Defense

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