Procedural defenses in criminal law are made with respect to the manner in which the defendant is treated by the justice system. The rationales of such defenses are usually separate from questions of the guilt or innocence of the defendant, and hinge rather on some form of abuse or misconduct in criminal procedure.
The criminal law system of the United States is carefully crafted to dispense justice to defendants in a fair, speedy and efficient manner. The constitutional rights of defendants and the principle of the presumption of innocence are meant to safeguard defendants against wrongful conviction and unfair treatment by prosecutors, and to ensure they have a fair and reasonable chance to defend themselves in a court of law. Unfortunately, criminal proceedings do not always function so smoothly. In the event of misconduct in the court or unconstitutional behavior on the part of prosecutors, judges, jury or the government itself, procedural defenses can be employed by the defendant's council, which in effect accuse the justice system itself of misconduct.
Some common procedural defenses are entrapment by the government, false confession by witnesses, falsified evidence, denial of a speedy trial, double jeopardy, prosecutorial misconduct, and selective prosecution.
Procedural defenses can be difficult to maintain successfully, since in effect they argue for the dispensers of justice to acknowledge their own conduct as unjust. Nevertheless, they are an important tool in the arsenal of criminal defense and an important safeguard against constitutional abuses by those in power.