Born in Saint Paul, Ramsey County, Minnesota, Devitt graduated from St. John's College Preparatory High School in Collegeville, Minnesota in 1930, and attended St. John's University from 1930 to 1932 before receiving a Bachelor of Laws from the University of North Dakota School of Law in Grand Forks, North Dakota in 1935, and a Bachelor of Science degree from the University of North Dakota in 1938.

He served in the United States Naval Reserve during World War II as a Lieutenant Commander from 1942 to 1946.

In 1979, Devitt presided over the criminal trial for the five Red Lake Reservation uprising defendants, imposing a 26-year prison sentence on uprising leader Harry S. Hanson Jr.[3] Devitt would also impose prison sentences ranging from 10 to 16 years against Hanson's four co-defendants.

He served as a judge of the United States Foreign Intelligence Surveillance Court from 1985 to 1992.

Devitt remained in senior status until his death, in Saint Paul on March 2, 1992.