The one Dallas cop killer who got away Research indicates suspect fell through cracks in 1916 slaying 09/01/2002 By TANYA EISERER / The Dallas Morning News When Officer Steve Elwonger was a rookie in 1982, he was told that the Dallas Police Department always "caught our man" when one of its officers was killed in the line of duty. But after looking into the January 1916 slaying of Officer W. Roy Thornton, he's not so sure the police have caught every cop killer. "As I was doing the research ... I found out that isn't the case," said Officer...