Mathis made the Pro Bowl as a returner with the Houston Texans in 2005, but he was injured for most of the last two seasons. He became a free agent this year when the Texans opted not to make him a qualifying offer at the end of the season.
Mathis has had two recent run-ins with the law. In December, he received a misdemeanor citation after his pit bull chewed through a fence and was behaving aggressively. In February, he was charged with assaulting his pregnant common-law wife, a charge that was later dropped at the woman's request.
The 24-year-old Mathis broke the NCAA record for career kickoff return average at Hampton, averaging 26.6 yards. He also holds the NCAA record for career kickoff returns for a touchdown with six.
The signing is a minor first addition for the usually big-spending Redskins, who uncharacteristically have de-emphasized the free agent market this year and are instead concentrating on this month's draft. Washington's only previous moves this offseason had been to re-sign some of their own free agents.