1972),[1] is decision by the United States Court of Appeals for the District of Columbia Circuit in which the Court held that a person is not responsible for criminal conduct if at the time of such conduct as a result of mental disease or defect, he lacked substantial capacity either to appreciate the criminality of his conduct or conform his conduct to the requirements of the law.

The case overturned the Durham rule for determining whether a defendant was not guilty by reason of insanity.

The Court ruled that the primary reason they were departing from the old test of insanity is that it put substantial dominance on the testimony of experts.

The American Law Institute provided a better framework in the majority's opinion because it took part of the reliance on experts away and focused on the acts and mental state of a defendant at the time he committed the acts constituting the crime.

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