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 Louisiana, criminal procedure is governed by the Louisiana Code of Criminal Procedure and relevant federal laws, which establish the rules and processes for handling criminal cases from investigation to trial and appeal. These procedures are designed to ensure that both the enforcement of criminal law and the protection of defendants' constitutional rights, such as the right to a fair trial, the right to counsel, and protection against self-incrimination, are upheld. The state's procedures cover various stages including arrest, initial appearance, preliminary examination, arraignment, pretrial motions, trial, and sentencing. Additionally, the U.S. Constitution, particularly the Fourth, Fifth, Sixth, and Fourteenth Amendments, provides a framework for protecting individual rights against unlawful searches and seizures, ensuring due process, and guaranteeing the right to a speedy and public trial by an impartial jury. Louisiana courts interpret and apply these procedures and constitutional protections in individual cases, and their decisions can be subject to appeal to higher courts, including the Louisiana Supreme Court and the federal court system.