A Level Law Practice Exam

The M'Naughten rules establish a standard for the insanity defense that requires proof of both a defect of reason caused by a disease of the mind and an inability to know the nature of the act or to understand that the act was wrong at the time it was committed. This means that to successfully use the defense of insanity, it must be demonstrated that the defendant had a significant mental impairment that impacted their ability to reason or recognize the consequences of their actions.

The requirement of a defect of reason indicates that there must be a substantial impairment in the mental faculties, often linked to a recognized mental illness. Additionally, proving that the defendant did not know the nature of their act or did not understand that it was wrong further solidifies the basis for the insanity plea. Thus, both components are essential and must be satisfied in order for the insanity defense to be applicable.

The other choices do not encompass the full criteria needed to support the insanity defense according to the M'Naughten rules, which makes option D, including both B and C, the correct choice.