Former NFL running back Lawrence Phillips has been charged with strangling his cellmate while locked up at Kern Valley State Prison in California. Phillips, 40, is in the midst of a 31-year sentence for choking his girlfriend and driving his car into three teens following a pickup football game. He's now facing a first-degree murder charge in connection with the death of 37-year-old Damion Soward in April. Phillips was a top college player at Nebraska before playing for the St. Louis Rams, Miami Dolphins, and San Francisco 49ers over a three-year professional career. (More NFL stories.)