Complex sentence: James Robert "Jim" Leavelle (born August 23,1920) is a Pearl Harbor veteran and the former Dallas, Texas, homicide detective who was escorting Lee Harvey Oswald through the basement of Dallas Police headquarters when Oswald was shot by Jack Ruby.
Split into simpler sentences: James Robert "Jim" Leavelle (born August 23,1920) is a former Dallas Police Detective. He was an Pearl Harbor veteran and the former Dallas, Texas, homicide detective who was escorting Lee Harvey Oswald through the basement of Dallas Police headquarters when Oswald was shot by Jack Ruby.