WHITEMARSH, Pa. -- A Canadian porn actress found stabbed to death last month may have been killed while shooting a film that was to have simulated the murder of a woman during sex, prosecutors said. DNA clues and a scrawled note referring to a "snuff" video connect photographer Anthony J. Frederick to the death of 23-year-old Natel King, whose body was found in a trash-filled ravine in March, District Attorney Bruce Castor said at a preliminary hearing Friday. Frederick's attorney, Daniel-Paul Alva, said his client had nothing to do with snuff videos. "We don't know who killed her," he said....