A Durham rule, product test, or product defect rule is a rule in a criminal case by which a jury may determine a defendant is not guilty by reason of insanity because a criminal act was the product of a mental disease. Examples in which such rules were articulated in common law include State v. Pike (1870) and Durham v. United States (1954). In Pike, the Superior Court of Judicature of New Hampshire wrote, "An accused is not criminally responsible if his unlawful act was the product of mental disease or mental defect."The insanity defense plea has been removed in a handful of states and left with the "guilt by insane" verdict. These states include, Montana, Idaho, and Utah.