He received a Bachelor of General Studies degree from the University of Michigan in 1979 and his Juris Doctor from the Detroit College of Law (now the Michigan State University College of Law) in 1983.

Prior to joining the federal bench, Cox was a trial judge in Michigan for the Wayne Circuit Court.

President George W. Bush nominated Cox to the United States District Court for the Eastern District of Michigan on September 10, 2004, and renominated him on February 4, 2005, to fill a vacancy left by Judge Lawrence Paul Zatkoff.

Due to the initial opposition of Michigan Senators Carl Levin and Debbie Stabenow, Cox's nomination was not voted on until June 8, 2006, when he was confirmed by voice vote.

[2] In 2009, Cox presided over the case of Canadian citizens Timothy McGuire and James Ryan, who sued the Royal Oak, Michigan police department for false arrest after they witnessed but did not participate in an assault of a fellow passenger on a bus they were riding on.