WH Painter Mcnaughton

The M'Naghten rule (pronounced, and sometimes spelled, McNaughton)is any variant of the 1840s jury instruction in a criminal case when there is a defence of insanity:that every man is to be presumed to be sane, and … that to establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or if he did know it, that he did not know he was doing what was wrong.[1]:632