As excellent a researcher as Roberdeaux is, and there can be little doubt of that, I've always found it of paramount importance to do my own research rather than rely on the work of others, regardless of how illustrious they are. Below is a close-up video of JFK in the Z-film. We see his head turn to the right as he waves and smiles to the crowds lined on Elm Street. I, personally, do not detect any great urgency in this head turn and the fact that he begins to smile and wave makes a mockery of any notion that he is responding to the sound of a shot.
Is he smiling and waving at the bullet as it passes by?
This is the very well documented moment when Mary Woodward and her colleagues call out to the President and the First Lady to look their way. This would explain why JFK begins to smile and wave. This is why Jackie turns her head from left to right. I too must respectfully disagree with any notion that JFK's head has snapped to the right as a result of hearing a shot. In fact, I find the idea ludicrous.
Calling an idea ludicrous isn’t being respectful of it Dan. But thanks for the video link. At least on my iPad and Chrome browser, if I go full-screen with the video, it is possible to pause it and then “grab” the control time bar at the bottom and make the video stop, or go forward or backward at any speed that you want to drag the control at. The first part, which shows the segment in which the limo occupants appear to be reacting to a missed first shot is clear enough to see all four of the VIP passengers. It appears to me that the first part of JBC’s reactions are similar to JFK’s reactions (until the wave by JFK) but lag behind JFK’s reactions by a little bit. They both initially appear to instinctively glance toward their spouses (a normal and instinctive male protective reaction) and one that JBC apparently didn’t remember accurately. Then both of them snap their heads to the right very quickly. JFK appears to have heard the loud shot but didn’t immediately recognize it as a shot, saw nothing that presented itself as a threat, and recovered his composure very quickly and began to wave back at the crowd. On the other hand, JBC appears to be continuing to try to turn as far to his right as he can in that seat. This would be in accordance with his testimony. Both Nellie Connally and Jackie turn to their right also. I really don’t believe that those reactions, from all four of them at roughly the same time, would be warranted by someone in the crowd calling out. After all, they were just leaving a huge crowd where a lot of people were doing just that.
There is a lot of other physical evidence that suggests an early missed shot. Off the top of my head I can name a few:
1. Rosemary Willis snaps her head back towards the TSBD and begins slowing down in order to stop. The spacing of the dots showing her path on the Roberdeaux map graphically illustrates the slow down. It can also be seen in the Z-film.
2. The Hughes film has a skip of a few frames at approximately this same time. It is believed it could only be due to Hughes’ reaction to the sound of the shot by lifting his finger pressure on the camera button for an instant.
3. The Dorman film has a huge jiggle upwards before being abruptly stopped at approximately this same time.
4. The Tina Towner film stops just before this same time, this agrees with her statement that the first shot sounded about the same time, or slightly after, she stopped filming.
5. It appears to me that the Zapruder film has a jiggle about the same time that JFK snaps his head to the right.
I have been trying to explore different possibilities with an open mind. But again, I cannot simply dismiss all the above physical evidence that suggests an early missed shot. There are also plenty of witness accounts that also suggest this that I haven’t listed.