Body of law that defines criminal offenses, regulates the apprehension, charging, and trial of suspected offenders, and fixes punishment for convicted persons. Substantive criminal law defines particular crimes, and procedural law establishes rules for the prosecution of crime. In the U.S., substantive criminal law originated for the most part in common law, which was later codified in federal and state statutes. Modern criminal law has been affected considerably by the social sciences, especially in the areas of sentencing, legal research, legislation, and rehabilitation. See alsocriminology.