McDonnell was a lieutenant colonel in the United States Army Reserve. BBA in administration in 1976. Immediately next graduation, he served as a clinical offer officer in the United States Army for four a long time. Under the 1998-2001 power-sharing arrangement among House Republicans and Democrats, he was Co-Chair of the Committee on the Chesapeake and its Tributaries in 2000-01. He turned Chair of the Courts of Justice Committee in 2003.