Castleton joined the firm in 2005. His focus is in litigation, with emphasis in municipality and public entity defense; employment law; general business and real estate litigation; and wills, trusts and probates. He previously practiced in a construction law and civil litigation firm. Before that, he clerked for Idaho Supreme Court Chief Justice Linda Copple Trout.
Castleton was a Distinguished Military Graduate of the Army ROTC program and served in the U.S. Army on active duty and in the National Guard as a field artillery officer. He is licensed to practice law in Idaho and the U.S. Court of Appeals for the Ninth Circuit.