The branch of law dealing with crime and punishment. In England the criminal law is founded in common law, substantially modified by statute in 1861, and further in the twentieth century. In Scotland criminal law is still, for the most part, common law, while the English common law of crime persists in the US, adapted in certain respects to the different circumstances there prevailing.
In most cases the application of criminal law is governed by the following basic principles of justice:
(i) Nulla poena sine lege. No act can be punished unless a law exists that forbids it, however immoral, antisocial or destructive it may be.
(ii) Criminal law must be clear and unambiguous, so as to give ‘fair warning’.
(iii) Criminal statutes are to be construed strictly and not extended by analogy.
(iv) Retroactive legislation is impermissible, unless expressly authorized by statute.
Such provisions are widely held to capture an important element in the idea of natural justice, and impose real constraints on judicial construction. They are tantamount to the theory that when deciding a case, the judge does not make law, but discovers it. This theory is, however, a theory about what must be thought by the participants in the judicial process, not a theory about what must be true for that process to be possible. See further hard cases.