Extracted from Case Closed by Gerald Posner (Little, Brown 1994).
THE home movie made by [Abraham] Zapruder, a Dallas dressmaker, serves as a time clock for the assassination. By figuring when the first and last shots took place, it is possible to know how much total time the assassin had. The third shot is the easiest to pinpoint. On the Zapruder film, the President is hit in the head at frame 313. No matter what number of shots they heard, the witnesses were almost unanimous that the head shot was the final one.
New Zapruder enhancements confirm that an early shot missed the President and the Governor [John Connally]. At frame 160, a young girl in a red skirt and white top, who was running along the left side of the President's car down Elm Street, began turning to her right. Not 1.5 seconds later, she had stopped, twisted completely away from the motorcade, and was staring back at the School Book Depository. When asked why she stopped, the girl, 10-year-old Rosemary Willis, said: 'I stopped when I heard the shot . . . I think I probably turned to look towards the noise, towards the Book Depository.' At the same time as she started turning, the enhanced film shows President Kennedy, who was waving as the car turned the corner, suddenly stop waving. He looked to the right towards the crowd, and then back to his left to [his wife] Jacqueline, as if to be reassured that everything was all right. As he began waving again, Mrs Kennedy's head abruptly twisted from her left to the right, the general direction of the School Book Depository.
Connally's recollections and actions confirm the shot. 'We had just made the turn, when I heard what I thought was a shot,' he told the Warren Commission. 'I instinctively turned to my right because the sound appeared to come from over my right shoulder.'The film reveals that the Governor's head turned from mid-left to far right in less than half a second, beginning at frame 162, when the Willis girl started turning around and the President stopped waving.
'Jiggle analysis' provides additional evidence. Tests have shown that gunshots produce detectable motion on film made with a hand-held camera. While sudden movement of Zapruder's camera may not prove a shot was fired, its absence is good evidence there was no shot.
The House Select Committee determined that there were four such noticeable movements, any of which could be evidence of a shot. The first significant blur was at frames 158-160, just as Oswald would have had to fire to avoid losing his target under a treethat would block his view for several seconds. The largest movement by Zapruder came at frames 313-314, the moment of the head shot.