Hatfield was admitted to the Montana bar that same year, commencing his practice in Great Falls.[2] He was chief deputy county attorney for Cascade County from 1959 to 1960 and served as judge of the Eighth Judicial District from 1961 to 1976. He was elected Chief Justice of the Montana Supreme Court in the 1976 general election, defeating long-time Associate Justice Wesley Castles with a vote of 199,536 (67.5%) to 95,947 (32.5%), taking office in January 1977.
United States Senate
On January 22, 1978, Montana Governor Thomas Lee Judge appointed Hatfield to the United States Senate to fill the vacancy caused by the death of Lee Metcalf for the term ending January 3, 1979. He served from January 22, 1978, until his resignation December 14, 1978. He was defeated for nomination in the Democratic primary in June 1978 by Congressman Max Baucus with Baucus getting 87,085 votes (65.3%) to Hatfield's 25,789 (19.3%). There were two other minor candidates in the race. After that nominating defeat, Hatfield remained in the Senate until his own resignation when the election of his successor, Baucus, was officially certified after the general election in November 1978. Max Baucus praised his former primary opponent for being "one of the most decent and thoughtful people I've had the privilege of knowing."[3]
Federal judicial service
On March 15, 1979, Hatfield was nominated by President Jimmy Carter to a seat on the United States District Court for the District of Montana vacated by Judge Russell Evans Smith. Hatfield was confirmed by the United States Senate on May 9, 1979, and received his commission the following day. He served as Chief Judge from 1990 to 1996, assuming senior status on February 9, 1996, and continuing to serve until the end of his life.[2] Hatfield was a resident of Great Falls from 1979 until his death on July 3, 2000.[4] He is buried in Riverside Memorial Park in Spokane, Washington.[5]
