Born in Montour Falls, New York, Elfvin received his Bachelor of Electrical Engineering degree from Cornell University in 1942 and was a member of Phi Kappa Tau fraternity there.
He earned his Juris Doctor in 1947 from the Georgetown Law school following service in the United States Navy as an electrical engineer in the Bureau of Ships during World War II, from 1943 to 1946.
Elfvin clerked for Judge E. Barrett Prettyman of the United States Court of Appeals for the District of Columbia Circuit from 1947 to 1948.
[2] Elfvin was confirmed by the United States Senate on December 20, 1974, and received his commission the following day.
Elfvin assumed senior status on July 1, 1987, and took inactive senior status on October 5, 2007, meaning that while he remained a federal judge, he no longer heard cases or participated in the business of the court.