John was born in Philadelphia, PA and is an alumnus of Northeast Catholic High School. He is a 1962 graduate and a member of the School's Hall of Fame. He is a 1966 graduate of the University of Pennsylvania where he majored in English Literature and played varsity football. He is best known for playing Deputy Police Commissioner William Rawls on HBO series The Wire from 2002 to 2008 and Colonel Edward Galson on Oz in 2001.
Doman also had cameos in the 1997 films Cop Land, the 2003 Mystic River and the film The Opponent.
On television, Doman has been in Star Trek: Deep Space Nine, Law & Order: Special Victims Unit, Borgia, Burn Notice, Law & Order and CSI: Crime Scene Investigation. He also portrayed Dr. Carl Deraad on Seasons 5 and 6 of ER, and has been introduced as bad-guy CEO Walter Kendrick on Season 2 of Damages. He played a small role in the famous action film, Die Hard with a Vengeance, as one of the site managers for the construction of a tunnel featured in the film.
Doman has also appeared in promotional advertisements for Versus television. The promotional videos' soundtrack is a rendition of Metallica's "One" from Apocalyptica's 1998 'Inquisition Symphony album.
Prior to embarking on a successful acting career he spent 20 years in the advertising business. He is a former Marine Corps officer and a Vietnam veteran.