Born in Camden, Arkansas, Hagen was in the United States Air Force from 1949 to 1952.
On October 7, 1993, Hagen was nominated by President Bill Clinton to a seat on the United States District Court for the District of Nevada vacated by Edward Cornelius Reed, Jr. Hagen was confirmed by the United States Senate on November 20, 1993, and received his commission on November 22, 1993.
He assumed senior status on November 28, 2003, serving in that capacity until his retirement from the bench on March 31, 2005.
In that capacity he arbitrated and mediated all manner of civil litigation, including intellectual property disputes, class-action lawsuits, gold mining claims, employment lawsuits and commercial contracts.
He worked nationwide, but primarily in the Reno, Las Vegas, and San Francisco Bay areas.