The United States Constitution is a complete code of criminal procedure. The Fourteenth Amendment guarantees due process of law in federal and state proceedings. Over one-half of the rights guaranteed in the bill of rights, guarantee rights to persons suspected of, charged with, and convicted of crimes. Most criminal cases are never appealed beyond the State Court level. The Model Code of Pre-Arraignment Procedure is the law in most states.
Criminal procedure is a method for enforcing the criminal law.
According to the supremacy clause Supreme Court precedents shall not be overturned by Congress. Day to day criminal procedure is mainly the business of the Federal Government. States may not expand the scope of a federal right beyond the federal minimum. The U.S. Supreme Court is the only one with the power to exercise judicial review. According to the Fundamental Fairness Doctrine, due process is a general command, requiring states to provide the rudiments of a fair trial.