Durham Rule | Definition

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

The Durham Rule, also termed the Durham standard, is a judicial guideline used to establish if a defendant’s criminal actions were caused by a mental illness.

The Durham Rule finds its roots in the landmark 1954 case, Durham v. United States. The United States Court of Appeals for the District of Columbia Circuit was responsible for this significant legal decision. The ruling was ground-breaking, introducing a new perspective into the criminal justice system.

Before this, mental illness was rarely considered a valid defense in criminal cases. But the court in the Durham case ruled differently. They decided that if a person’s criminal actions were the direct outcome of a mental disorder, they couldn’t be held accountable in the same way.

Understanding the Durham Rule

At its core, the Durham Rule hinges on mental illness causing criminal behavior. For a defendant to use this as a defense, they must prove this relationship. The mental illness must be the primary cause, not just a contributing factor. If a defendant fails to demonstrate this causal relationship, the Durham Rule won’t apply.

If the defendant successfully establishes that their mental illness caused their criminal behavior, they could be found not guilty by reason of insanity. This doesn’t mean they go free. Instead, they usually receive treatment for their mental illness.

The “Right and Wrong” Aspect

The Durham Rule also considers the defendant’s ability to discern right from wrong. A key question is whether their mental illness made it impossible for them to understand their actions’ legality or morality.

If the defendant could not tell right from wrong due to their mental illness, this could support their defense under the Durham Rule. Similarly, if their mental illness prevented them from adhering to the law, the Durham Rule might apply.

Implementation and Influence

In practice, the Durham Rule has been significant but also controversial. Some people argue it allows defendants to escape punishment by claiming mental illness. Others, however, appreciate its recognition of mental health’s role in criminal behavior.

Many states rejected the Durham Rule due to its potential for misuse and its lack of clarity. They found it challenging to establish the direct cause-and-effect relationship between mental illness and criminal behavior. Despite this, the rule influenced later insanity defense laws, including the Model Penal Code’s test for legal insanity.


In essence, this rule introduced the concept of mental illness as a possible defense in criminal cases. While it has faced criticism and isn’t widely used today, its influence can still be seen in current legal practices around insanity defenses. The Rule thus plays a critical role in the intersection of mental health and the law.

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Last Modified: 05/18/2023

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