" The M’Naghten Rule states: To establish a defense on the ground of insanity it must be clearly proved, that, at the time of committing the act, the party accused was laboring 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 that what he was doing was wrong. "

― John Grisham , A Time for Mercy (Jake Brigance, #3)