CASE ANALYSIS: R v McNaughton (1843) 8 E. R. 718

Actus Non Facit Reum, Nisi Mens Sit Rea` is a Latin maxim that means that an act does not make the person guilty unless the mind is also guilty.1 This particular maxim identifies the two important elements necessary to convict of the crime committed. The two important elements are Mens Rea and Actus Reus, with the mental and physical elements involved, respectively. For a person to be legally responsible for an act, criminal intent is required, and therefore the ability of the perpetrator to establish criminal intent is a relevant consideration in determining the person's criminal responsibility. However, due to immaturity of age or lack of mental faculties, an individual may not have sufficient mental faculties to form a criminal intent. When such a defect is caused by mental illness, a person is said to be insane. A person who has a natural handicap to differentiate between right and wrong or good and bad, such as young children under a certain age, idiots, crazy, therefore is not punishable. Stephen states in his Compilation of Criminal Law that “no act is a crime if the person who does it, is at the same time when it is done prevented either by defective mental power or by any disease affecting his mind from knowing the nature and quality of the act or from knowing that the act is wrong”.2 Over the years, the defence of the insane has developed through various precedents and laws. The McNaughton case, dating back to the 19th century, marks a milestone in the defence of insanity. The principle or rule in McNaughton's case is a legendary principle related to the defence of insanity.