The insanity defense is when a person is not charged as guilty after he commits a crime while being mentally unstable. The rules and regulations related with insanity defense are pretty debatable as mental insanity can be a very good excuse to get away from the possible punishments. There are many tests regarding the insanity defense to prove if the person is mentally unstable or not. One of the main tests is the M’Naughten Rule which had been named based on the case of Daniel M’Naughten who got free from the charges because of his insane mental condition. He planned to murder the personal secretary of the president of UK.