Harris was a sixth-round draft pick by Chicago in 2005 who has played for the Bears, Panthers and Lions, starting at least seven games in each of his first seven seasons. He played in 11 games in 2011, seven with the Bears and four with the Lions, with eight starts.
His most productive year was in 2010, when he started all 16 games with Chicago and finished with a career-high five interceptions. Harris was not with a team this season until the Jaguars signed him Monday.
Jacksonville lost starting safety Dwight Lowery to an ankle injury against Chicago on Oct. 7. Lowery is expected to miss two to three weeks.