in law, is used for any subtile endeavor to put aside truth, or to escape the punishment of the law, which will not be endured. Thus, if a person says to another that he will not strike him, but will give him a pot of ale to strike him first, and accordingly he strikes, the returning of it is punishable; and if the person first striking be killed, it is murder; for no man shall evade the justice of the law by such a pretence to cover his malice.