Criminal law is an amalgam of moral judgments, policy decisions, and constitutional limitations. The legislature delineates social from anti-social behavior and prescribes punishments according to contemporary social mores and policy considerations. This power of the legislature is conscribed by constitutional requirements of process, whereby the rights of the accused are protected from arbitrary or excessive legislation. In enforcing these standards, the judiciary applies a combination of constitutional analysis, precedent, and legal theory. These elements, once combined, become “the law.”

Traditionally, the criminal process identifies a set of morally culpable facts, forces the government to prove beyond a reasonable doubt that these facts are true, and then creates a punishment which turns on the relative moral severity of the proven facts. This process is evident in the Fourth, Fifth, and Sixth Amendments, and in the Supreme Court’s rulings in In re Winship and Mullaney v. Wilbur. The moral severity of the facts proven thus provide a framework that gives criminal punishments their meaning.

These traditional concepts have been challenged by two developments. The first was the creation of affirmative defenses which sever facts relevant to moral guilt from facts relevant to the adjudication of legal guilt. Once distinguished from guilt facts, affirmative defense facts do not need to be proven by the prosecution but must be disproved by the defense during the trial. Affirmative defenses were created to advance modem penology by allowing defendants to experiment with new exculpatory theories. Examples of affirmative defense facts may be facts relating to insanity or emotional disturbance.