Navigating the Insanity Defense: Its Application and Justification in Missouri Law

Understanding the insanity defense is a critical part of comprehending the broader spectrum of criminal law in Missouri. It's a complex legal concept with deep roots in societal values, moral considerations, and the basic tenets of justice. This guide aims to shed light on the insanity defense, how it's applied in Missouri, and the public policy justifications behind its existence.

Understanding the Insanity Defense

At its most basic, the insanity defense is a legal strategy asserting that the defendant, due to a mental illness, was incapable of understanding the nature or wrongness of their actions at the time of the offense. If successful, this defense can result in a verdict of "not guilty by reason of insanity."

The Insanity Defense in Missouri: The M'Naghten Rule

Missouri adheres to a legal standard known as the M'Naghten Rule for insanity defenses. According to this rule, a defendant may be considered legally insane if, at the time of the alleged criminal act, they were suffering from a mental disease that either prevented them from understanding the nature and quality of their actions or from knowing that what they were doing was wrong.

Public Policy Justifications

The insanity defense, though often misunderstood or stigmatized, is a crucial part of our justice system grounded in public policy justifications.

1. Moral Ethical Considerations: Our society is based on the principle that individuals are only punishable if they are capable of controlling their behavior and understanding the implications of their actions. Penalizing someone incapable of such understanding due to mental illness seems contrary to these principles.

2. Treatment Over Punishment: The insanity defense allows for individuals with severe mental illnesses to be placed in a mental health facility rather than a prison. It's believed that such individuals are better served by treatment and rehabilitation than by punishment.

3. Deterrence: The insanity defense doesn't offer an easy way out. Those adjudged not guilty by reason of insanity often spend as much, if not more, time in psychiatric hospitals as they would in prison. Therefore, it doesn't incentivize criminals to feign mental illness to escape punishment.


The insanity defense represents a critical intersection between the legal and mental health systems. It's a complex area of law that requires an expert understanding of both legal principles and psychological conditions. If you or a loved one is facing criminal charges in Missouri and believe the insanity defense might apply, it's essential to consult with a knowledgeable attorney who can navigate these complex issues and advocate for your rights.