What is the M'Naghten Rule? How did this rule come into existence?

Criminology?

The M'Naghten rule talks about the insanity defense plea.As per this rule a criminal is not guilty if at the time of committing the act the defendant did not  know the nature or quality of his/her action.In other words the criminal committing the crime fails to understand that his/her actions are wrong or is not in a mental state to understand that he/she has committed a crime.The test is based on the notion that the defendant is suffering from some disease that makes him incapable of distinguish between right and wrong.The rule was formed in the year 1843 by the judges of England,during the  trial of Daniel M’Naghten case. M'Naghten was  charged for attempt to murder Edward Drummond, whom M'Naghten had mistaken for UK Prime Minister Robert Peel.