involves prosecution by the government of a person for an act that has been classified as a crime. In a criminal case the state, through a prosecutor, initiates the suit. Persons convicted of a crime may be incarcerated, fined, or both. A "crime" is any act or omission (of an act) in violation of a public law forbidding or commanding it. Though there are some common law crimes, most crimes in the United States are established by local, state, and federal governments. Crimes include both felonies (more serious offenses -- like murder or rape) and misdemeanors (less serious offenses -- like petty theft or disorderly intoxication.
Felonies are usually crimes punishable by imprisonment of a year or more, while misdemeanors are crimes punishable by less than a year. However, no act is a crime if it has not been previously established as such either by statute or common law. All statutes describing criminal behavior can be broken down into their various elements. Most crimes (with the exception of strict-liability crimes) consist of two elements: an act, or "actus reus," and a mental state, or "mens rea." Prosecutors have to prove each and every element of the crime to yield a conviction. Furthermore, the prosecutor must persuade the jury or judge "beyond a reasonable doubt" of every fact necessary to constitute the crime charged.