The Federal Rules of Criminal Procedure are the procedural rules that govern how federal criminal prosecutions are conducted in United States district courts, the general trial courts of the U.S. government. As such, they are the companion to the Federal Rules of Civil Procedure. The admissibility and use of evidence in criminal proceedings (as well as civil) is governed by the separate Federal Rules of Evidence. The U.S. Constitution, the Federal Rules and the federal court system's interpretations of both provide guidance and procedural canons that law enforcement must follow. Failure to follow such procedure may result in the suppression of evidence or the release of an arrested suspect.
Similarly, individual states have their own codes of criminal procedure of which many closely model the Federal Rules. While state constitutions and procedural rules may increase the protection afforded to criminal defendants, they may not offer less protection than that guaranteed by the U.S. Constitution.
