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 Hawaii, criminal procedure is governed by both state statutes and the Hawaii Rules of Penal Procedure. These rules outline the steps for conducting criminal trials, from investigation to arrest, charging, trial, and the appeals process. They ensure that the rights of the accused are protected throughout the criminal justice process, in accordance with the U.S. Constitution, particularly the Fourth, Fifth, Sixth, and Fourteenth Amendments, which guarantee rights such as due process, protection against self-incrimination, a fair and speedy trial, and legal representation. Hawaii's criminal procedure also includes provisions for bail, plea bargaining, and the treatment of evidence. Federal laws and the Federal Rules of Criminal Procedure may also apply, especially in cases where federal jurisdiction is invoked. State and federal court opinions in Hawaii interpret these rules and rights, contributing to the body of law that shapes criminal procedure in the state.