Controlling force; irresistible compulsion; a power or impulse so great that it admits no choice of conduct. When it is said that an act is done “under necessity,” It may be. in law, either of three kinds of necessity: (1) The necessity of preserving one’s own life, which will excuse a homicide; (2) the necessity of obedience, as to the laws, or the obedience of one not sui Juris to his superior; (3) the necessity caused by the act of God or a stranger. See Jacob; Mozley A Whitley. A constraint upon the will whereby, a person is urged to do that which his judgment disapproves, and which, it is to be presumed, his will (if left to itself) would reject. A man. therefore, is excused for those actions which are done through unavoidable force and compulsion. Wharton. Necessity, homicide by. A species of Justifiable homicide, because it arises from some unavoidable necessity, without any will, intention, or desire, and without any inadvertence or negligence in the party killing, and therefore without any shadow of blame. As. for instance, by virtue of such an office as obliges one, in the execution of public justice, to put “a malefactor to death who has forfeited his life to the laws of his country. But the law must require it otherwise it is not justifiable. 4 Bl. Comm. 178.