In 1963 the Montana Legislative Assembly established the Montana Criminal Law Commission. The eleven-member Commission was to review the criminal code and suggest changes resulting in uniform and simplified procedures and laws. Associate Justice Wesley Castles of the Montana Supreme Court was appointed to the Commission and served as its chairman.

The Commission completed the first phase of its project in 1966. A proposed code of criminal procedure was submitted to the Supreme Court and all members of the bench and bar for consideration and suggestions. The proposed code was passed by the 1967 Legislative Assembly and became effective on January 1, 1968. The second phase of the revision consisted of the substantive criminal law which provided for definitions of crimes. The proposed code, including several minor changes in the 1967 procedure code, was also submitted to the bench and bar of the state. The proposed criminal code was passed by the 1973 Legislative Assembly and became effective on January 1, 1974.

During late 1973 and early 1974, seminars on the new criminal code were conducted by members of the Commission. Sponsored by the Montana Supreme Court, the Criminal Law Commission, and the Montana Bar Association, grant funds were provided by the State Board of Crime Control.