Dur·ham rule /'du̇r-əm-, 'dər-/ n [from Durham v. United States, 214 F.2d 862 (1954), a case heard by the District of Columbia Court of Appeals that established the rule]: a rule of criminal law used in some states that holds that in order to find a defendant not guilty by reason of insanity the defendant's criminal act must be the product of a mental disease or defect compare irresistible impulse test, m'naghten test, substantial capacity test
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.