Bears sign defensive back Derrick Martin

The Bears signed safety Derrick Martin on Sunday, the club said. Martin, 28, will vie to make the Bears’ roster as a reserve defensive back and special-teams player. He appeared in five regular-season games for New England in 2012 and recorded five tackles on defense. Martin has also had stints with the Ravens (2006-2008), Packers (2009-2010) and…