In criminal law, guilt is the state of being responsible for the commission of an offense. Legal guilt is entirely externally defined by the state, or more generally a "court of law". Being "guilty" of a criminal offense means that one has committed a violation of criminal law, or performed all the elements of the offense set out by a criminal statute. The determination that one has committed that violation is made by an external body (a "court of law") after the determination of the facts by a finder of fact or “factfinder” (i.e. a jury) and is, therefore, as definitive as the record-keeping of the body. For instance, in the case of a bench trial a judge acts as both the court of law and the factfinder, whereas in a jury trial the jury is the trier of fact and the judge acts only as the trier of law. Thus, the most basic definition is fundamentally circular: a person is guilty of violating a law if a factfinder in a court of law so says.

Philosophically, guilt in criminal law is a reflection of a functioning society and its ability to condemn individuals' actions. It rests fundamentally on a presumption of free will, in which individuals choose actions and are, therefore, subjected to external judgement of the rightness or wrongness of those actions. As described by Judge Alvin B. Rubin in United States v. Lyons (1984):

An adjudication of guilt is more than a factual determination that the defendant pulled a trigger, took a bicycle, or sold heroin. It is a moral judgment that the individual is blameworthy. Our collective conscience does not allow punishment where it cannot impose blame. Our concept of blameworthiness rests on assumptions that are older than the Republic: man is naturally endowed with these two great faculties, understanding and liberty of will. Historically, our substantive criminal law is based on a theory of punishing the viscious [sic] will. It postulates a free agent confronted with a choice between doing right and wrong, and choosing freely to do wrong.