Before entering private practice, Warren served as Chief of the Civil Division for the U.S. Attorney's Office in the Middle District of Florida from 1994 to 2008.  He and the lawyers under his supervision handled hundreds of cases on behalf of the United States, its agencies and officers.  These included cases involving personal injury, medical malpractice, employment discrimination, civil rights, mortgage foreclosure, debt collection, adversary proceedings in bankruptcy, health care fraud, and defense procurement fraud.