The Federal Rules of Criminal Procedure govern criminal proceedings and prosecutions in the U.S. district courts, the courts of appeals, and the Supreme Court. Their purpose is to “provide for the just determination of every criminal proceeding, to secure simplicity in procedure and fairness in administration, and to eliminate unjustifiable expense and delay.” Fed. R. Crim. P. 2. The original rules were adopted by order of the Supreme Court on December 26, 1944, transmitted to Congress on January 3, 1945, and effective March 21, 1946. The rules have since been amended numerous times, most recently in 2014.

http://www.uscourts.gov/file/document/rules-criminal-procedure-0