The basic elements of a crime are actus reus, based on the fundamental tenet that the prosecution must prove that the accused committed the act beyond a reasonable doubt, and mens rea, the mental element based on the free will ethic. The mental element consists of intention, recklessness, and occasionally, negligence. Mens rea is usually a subjective test of the accused's intention. The test of liability is based on an external standard of what the reasonable citizen would have intended or foreseen. Defenses to crime include mistake of fact, self-preservation, passion, overwhelming circumstance, and insanity. Crime consists of those behaviors that are so defined by law; moral, social, and political considerations affect the definitions. The relationship between law and morals is an uneasy one, although laws often contain built-in moral positions, and judges often apply moral reasoning in their decisions. The criminal law is conservative and is primarily interested in proof, based on intricate rules of evidence designed to protect the accused and ensure fairness. 5 references. (Author summary modified)