Judge Mahan is a longtime resident of Las Vegas, having lived and practiced law there continuously since 1973. He was born in El Paso, Texas, during the Second World War and he grew up in Grand Junction, Colorado.
Judge Mahan attended the University of Charleston, West Virginia, and following graduation, he served in the United States Navy from 1966 to 1969.
Upon receiving his honorable discharge, Judge Mahan attended Vanderbilt University Law School where he was selected for Vanderbilt’s national moot court team. Following graduation from law school, Judge Mahan was admitted to practice in Nevada, the Ninth Circuit Court of Appeals, the United States Tax Court, and the United States Supreme Court.
In 1982, Judge Mahan and Frank A. Ellis III formed the law firm of Mahan & Ellis, Chartered, where they practiced law primarily in the areas of business and commercial litigation for seventeen years. Judge Mahan was named to “Who’s Who in America” and “Who’s Who in the World,” as well as “Who’s Who in American Law.”
In February 1999, Governor Kenny Guinn appointed Judge Mahan to the Clark County Eighth Judicial District Court.  In the biennial Review Journal poll of lawyers in Clark County, he was the highest rated district judge in 2000 and 2002.
In 2001, United States Senator John Ensign nominated Judge Mahan to the United States District Court. Judge Mahan formally took the Oath of Office on February 1, 2002.  From 2005 – 2012, he served as an adjunct professor at the William H. Boyd School of Law.  He has served on the Board of Advisors for the Vanderbilt Law School since 2014.