A former FBI agent headed to court Friday to be sentenced for a deadly drunken driving crash in Prince George's County.Adrian Johnson was convicted in October on charges of vehicular manslaughter and homicide by a motor vehicle while intoxicated.The accident, which happened almost two years ago in Brandywine, left 18-year-old Lawerence Garner dead.Johnson now faces up to 13 years in prison. His lawyers argue that the crash was unavoidable.