A few comments and questions only on the parts in question.
A bullet passing between the C7 and T1 vertebrae, glancing off the transverse process of T1, would almost inevitably sever, or at least severely damage, the nerve marked T1 in the diagram, affecting in particular the Ulnar nerve which has its roots in the "T1" (and C8) nerve. The Ulnar nerve runs the length of the arm, entering the hand where it "flexes the ring and little fingers at the distal interphalangeal joint".
A bullet severing the Ulnar nerve may cause the hand to rapidly contract, however the Ulnar nerve only controls the flexion of the ring and little fingers.
I wish I could find a clearer image than the one below but there is a very strange aspect of JFK's hands in reaction to being shot. One might expect someone to 'clutch' at their throat if they were shot there but JFK doesn't do this. Instead he appears to clench his hands into fists and thrusts them under the area of his chin.
But even this is not quite correct. A clear image (I've seen one but can't find it at the moment) reveals that JFK appears to be 'pointing' at his throat:
I believe this indicates the bullet has severed his Ulnar nerve, causing some of his fingers (ring and little) to instantly clench shut but leaving his index finger unaffected and in a 'pointing' position.
I’m not sure about damage to the ulnar nerve, which looks to branch from the medial cord just before the armpit. Not sure how the bullet would go down there to sever the ulnar nerve, did you mean damage to the nerve root further back up near the transverse process that only effected the ulnar nerve?
It is important to note a secondary explosion, referred to as "dieseling", that occurs within the cavitation. I believe this plays an important role in the headshot itself.
I have heard of dieseling effect, but not heard of any theory of an internal explosion in the head by dieseling. That’s an interesting new one to me.
By the moment of the headshot JFK's arms have come down and his head has slumped forward, if anything this is indicative that his neck has totally relaxed by the time of the headshot. A frame from just before the headshot shows this relaxed posture more clearly:
Based on the neurological references I found, I think that spastic paralysis is what you are seeing happen in the upper torso area around the z222 strike location, and it was dynamic here, not instantaneous, and progresses from ~z226-z254 and then it was effectively in place for the near term (did not just instantly go away in a few seconds) and was complete with the stiffness set in and basically in place, where he looked the same from ~z262-312 and where his position did not change much at all. I thought he effectively looked “locked in place” and ITEK called him “frozen” up to z312. There were small changes in posture witch I attribute to the forces on him over this time frame like Jackie trying to pull down on his extended arm and of course gravity doing some work on the body.
Bottom line, I don’t believe upper body spastic paralysis would set in so dramatically and then passively totally disappear in less than 5 seconds. I don’t believe the people that I showed in photographs with similar spastic paralysis symptoms had those symptoms photographed only within 5 seconds of their occurrence before their symptoms disappeared.
But as you saw in my earlier discussion, an active intervention like the z313 head strike could facilitate flaccid paralysis setting in, much more extensively and quicker, in as soon at 0.2 seconds.
What you may be thinking about is his bending forward in this z262-312 timeframe, and I could see where you could see it as a relaxation or slump. If the spasticity did not effect his lower torso/abdominals, then that part of him might have leaned forward and slumped forward. Perhaps the blow to the back would nudge him forward a little. If however, spasticity was able to extend that far down then it might cause some forward bending, if so then that is what is observed.
In either case, his bending forward would continue to where the forward pressure on the back brace became equalized by the back brace restoring force pushing backwards which would keep his body at an equilibrium or neutral tilted position until z313 when it was displaced some more forward beyond that neutral position, loading up the back brace with a cantilever like force that quickly began to push the torso backwards as indicated by the upper torso’s position motion measured over time.
Net, there is plenty of reason to believe there was stiffness, at least in the upper torso, through z312.
The gif below was created by John Mytton and clearly shows the massive injury to the top of JFK's head:
I haven’t studied the dynamics of the head rupture and relative to the x-rays etc., but doesn’t all this agree with what Larry Sturdivan said in that it can be difficult to determine the direction of a bullet just by looking at the blowout? I believe this would be because the internal cranium pressure rises high in all directions and would blow out the weakest area which could be set up by a bullet exit, or just a weak skull bone area. I’m thinking one of weakest areas of the skull is the temple area, so if a bullet or fragment exited that area, it would be pretty ripe for a blowout starting.
If there was any jet effect it would be related to these lines of ejected material being blown from the top of JFK's head. The direction of any jet effect can be seen to have no component that would drive JFK's head backwards:
I thought the white dots were supposed to be skull fragments tumbling in the air during the camera exposure, with the bright side showing up after each rotation. If so, this would represent only two pieces of mass. Wouldn’t you want to consider all the mass ejected to do a mass and momentum balance when making a judgement on if there was any jet effect in play? It is fair to ignore all that red fan gunk ahead of his forehead and face? Should brain, scalp, blood, connective tissue, and perhaps other fragments be excluded? Even if one did ignore all this other stuff, wouldn’t two vectors representing the recoil of these two displayed vectors have some down and to the back components?
But what is the cause of the upwards explosion of skull and brain matter that lacerates the scalp?
The answer is "cavitation". Take one more look at this video posted above demonstrating cavitation caused by a bullet. It is this force acting on the compromised skull that, quite literally, blows the top of the head off.
I agree with you here, the high internal cranial pressure would create havoc. Everyone uses the term but I wish there was another word besides "cavitation" to describe a high internal pressure.
After the neck shot JFK has a almost instantaneous reflex reaction causing his body to stiffen as his elbows shoot up to their full extent.
His body then relaxes and his head slumps forward. When the shot hits the back of his head it drives it forward and downward. Having nowhere else to go, his head rebounds upwards and backwards in the characteristic "back and to the left" motion.
It looks like the main differences here to explain all JFK’s motion are just related to the models we have in place. You have a head bounce off the chest with no jet effect involved as the process, whereas my assumptions are different. Beyond that many of the observations are similar.
