Criminal law or penal law is the body of statutory and common law that deals with crime and the legal punishment of criminal offenses. There are four theories of criminal justice: punishment, deterrence, incapacitation, and rehabilitation. It is believed that imposing sanctions for the crime, society can achieve justice and a peaceable social order. This differs from civil law in that civil actions are disputes between two parties that are not of significant public concern.  The process begins, obviously, with an alleged crime. A complainant makes an accusation, which is investigated by the police, acting as agents of the government. The police file a document, in most jurisdictions known as a complaint, with a court in the appropriate jurisdiction. If the alleged offense is classified as a felony, the Constitution of the United States requires that the case be referred a grand jury for an indictment. An indictment is the official charging instrument accusing the defendant of criminal conduct.  The interests of the state are represented by a prosecuting attorney, while the interests of the defendant are represented by his or her defense attorney. While the specific process varies according to the local law, in virtually every jurisdiction the process culminates with a trial, followed by appeals to higher courts.  Criminal statutes spell out the exact circumstances which constitute a crime. These circumstances are known as the elements of the offense.  Unless all the elements are proven by the prosecuting authority, the defendant is not guilty of the offense. There are three kinds of elements: the act itself, the actus reus, the requisite mental state, the mens rea,  and the attendant circumstances. As an example, the common law definition of burglary was as follows: unlawful entry into a dwelling house at night with the intent to commit a felony therein. It is the duty of the prosecution, therefore, to prove not merely the act (the entry), and the mental state (the intent to commit a crime), but all the attendant circumstances (that it was a dwelling house, and that it was at night). Most modern criminal statutes have, among other changes, eliminated the "at night" element.  In defense, the accused could argue that he had no intent to commit a crime inside the house, that it occurred during the day, or that his entry was lawful. He could also, of course, argue that the incident never happened, or that someone else committed the offense.