Principle: When an act, which would otherwise be an offence, is not that offence by reason of the youth, the want of maturity of understanding, the unsoundness of mind or the intoxication of the person doing that act, every person has the same right of private defence against that act which he would have if the act were that offence. Nothing is an offence which is done in the exercise of the right of private defence.

Facts: A, under the influence of madness, attempts to kill B. B in order to save his life causes grievous hurt to A.