Criminal procedure is the process related to the investigation, arrest, charging, and conviction or acquittal of a criminal defendant. Much of criminal procedure is comprised of processes and rules through which the government (state, federal, or municipal) enforces substantive criminal law and through which a criminal defendant’s Constitutional and other rights are protected.

The law of criminal procedure is primarily located in the applicable state or federal rules of criminal procedure and state and federal court opinions interpreting and applying Constitutional and other legal rights.

In Arizona, criminal procedure is governed by both state statutes and the Arizona Rules of Criminal Procedure, which outline the process from investigation to trial for criminal cases. These rules ensure that a defendant's rights, as guaranteed by the U.S. Constitution and Arizona Constitution, are protected throughout the criminal justice process. This includes the right to due process, the right to a speedy and public trial, the right to counsel, and protection against self-incrimination and double jeopardy, among others. Federal laws and the Federal Rules of Criminal Procedure also apply when federal crimes are at issue. Arizona courts, including the Arizona Supreme Court, interpret these rules and rights through court opinions, which provide precedents for future cases. It is important for defendants to have an attorney who understands these complex procedures and can navigate the system to protect their rights.