Mc ‧ Naugh ‧ ten Rules, the /məkˈnɔːtn ˌruːlz/ BrE AmE , M'Naghten Rules, the
the rules in English law which say that, if it can be proved that someone did not know what they were doing when they carried out a crime or did not know that it was wrong, then they can ↑ plead ↑ insanity (=give madness as an excuse for their actions) . The rules were established as a result of the case of Regina v. McNaughten in 1843.