If there is some question of alteration of the Z film , which means frames being removed or added? Then I must ask why then did not the conspirators do a better job of editing so that the MC rifle shots would appear to be spread over 6-7 seconds rather than what the Z film as we have been presented shows as only a 4.8 sec spread between Z224 reactions of JFK and JC and the Z 313 last shot?
There is something which SEEMs peculiar about the head shot blood spray disappearing in only one frame (1/18th of a second ).
I’m not sure this quick dissipation was ever replicated by the 2003 Beyond Conspiracy documentary , however , they did manage to replicate the forward ejection of brain matter.
It’s the Z312–Z313 frames which show a 1/18th sec forward movement of JFKs head that would probably be the frames that were altered because without that little detail, the general perception of the public would be (as it was at first public viewing of the Z film) that the “back and to the left” movement of JFKs head was a clear indication the head shot came from the front of the limo.
I guess you haven't read most of my replies herein. JFK starts reacting long before Z224, as the HSCA PEP noted, as we know the WC's experts recognized, and as Olson and Turner noted, etc., etc.
In wound ballistics tests, the particulate spray from head shots remains visible for at least six frames, which only makes sense when you think about it. Another problem with the spray in the Zapruder film is that no spray blows backward, yet we know that blood and brain were splattered on the trunk, on the follow-up car, and on the two left-trailing patrolmen. Hargis was hit so hard by the spray that he thought he himself had been hit (and he was only moving about 11 mph, and the film shows no spray into which he could have driven of that could have hit him).
The Z312 forward head movement is highly debatable. I've cited it because WC apologists cited it for years after Dr. Alvarez detected it. Subsequent research has found sound reasons to believe that the movement is an optical illusion. A much more obvious and faster forward movement occurs from Z328-330. A gunshot impulse on the Dallas dictabelt recording occurs at right around Z328. For mor info on this, see British research Martin Hay's review of Josiah Thompson's 2021 book
Last Second in Dallas:
https://www.kennedysandking.com/john-f-kennedy-reviews/last-second-in-dallas-by-josiah-thompson.
I notice that WC apologists seem reluctant to deal with the Knott Laboratory refutation of the SBT mentioned and documented in the OP. Knott Lab, a forensic engineering and animation lab, has proved that Connally's position and back wound make the SBT impossible. Knott Lab engineers conducted a laser test in Dealey Plaza, collecting millions of data points, converted the data into 3D imagery, and determined that the SBT is impossible because Connally's back wound does not and cannot align with a bullet fired from the sixth-floor window and exiting JFK's throat. Here's a video on the Knott Lab study:
Why the 'Single Bullet Theory' in JFK Assassination Is ImpossibleAs I noted in the OP, the video has already had nearly half a million views since being posted about a month ago.
Of course, Dr. Mantik destroyed the SBT back in the 1990s when he produced an overhead scan of a man with dimensions closely resembling JFK's dimensions and showed that any bullet going from the back wound to the throat wound would have had to smash through the spine. WC apologists are still in denial about this powerful evidence. They've produced goofy graphics that move the back wound in order to enable the bullet to miss the spine.
