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 Oklahoma, criminal procedure is governed by a combination of state statutes, the Oklahoma Rules of Criminal Procedure, and federal law, including the U.S. Constitution. These laws and rules outline the steps and legal protections involved in the criminal justice process, from investigation and arrest to trial, sentencing, and appeals. The Fourth, Fifth, Sixth, and Fourteenth Amendments to the U.S. Constitution provide the foundation for many procedural protections, such as the right to a fair trial, the right to counsel, protection against self-incrimination, and the right to be free from unreasonable searches and seizures. Oklahoma's statutes and rules of criminal procedure further detail the specific processes to be followed in the state's criminal justice system, ensuring that a defendant's rights are upheld throughout the process. This includes procedures for arrest warrants, preliminary hearings, bail, arraignment, pretrial motions, plea bargaining, jury selection, trial, and post-conviction relief. Oklahoma courts interpret and apply these rules and constitutional principles to individual cases, creating a body of case law that shapes the application of criminal procedure in the state.