A new perspective on “Back and to the Left” in the Z-film

[Dan O'meara]

I’m glad you discussed this, as it will be something for me keep my eye on for possible future use. But at this time I don’t agree enough with your statements to make large changes in the modeling. Here are some of the "statements" I disagree with and reasons why I disagree:

Clearly you've put a lot of time into this aspect of the case but there are key issues I have to disagree with, in particular the notion of neck paralysis at the moment of impact and the so-called jet effect.
Understanding the mechanics of the headshot is of immense importance as, in my opinion, the "back and to the left" motion is the cornerstone of the majority of "multiple shooters" conspiracy thinking. Watching the Z-film in real time it is very difficult to get away from the intuitive perception that the "back and to the left" motion can be caused by anything other than a shot from the right front but a close analysis of the headshot reveals this motion was  caused by a shot hitting JFK's head from behind.

“there is zero evidence neck paralysis occurred”

All I can do is to mention the basis I used for the assessment that there was significant neck stiffness (in addition to shoulder, arms, hands and fingers).

1) It is called spasticity or spastic paralysis due to damage to the lower cervical part of the spine and the brachial plexus. In this case via a bullet transit that occurred circa z222.

https://sites.google.com/view/spastic-paralysis/home

2) Some Neurological opinions. From the Study Slide 54 or video time 2:07:00

Comments from Dr. Robert Artwohl explaining why we saw the arms stiffening upward.
“JFK’s reaction to the neck wound was, for all intents and purposes, instantaneous to the hit at Z-223/224. As the bullet passed through his neck, the pressure cavity caused an immediate and wide spread stimulation of all the nerves in the immediate vicinity, that is of the brachial plexus, the large group of nerves that emerge from C5-T1. These are the nerves that supply motor function to the arms.”

Comments from neurologist Dr. Strully in a letter sent by Dr. Strully to Dr. Robert Artwohl, dated April 9, 1994 as to an even greater possible extent of the muscle contractions.
 "Before all else, it is necessary to remember that this assassination reveals a sequence of neural responses initiated in the neck by the shock wave and cavitation induced by the bullet in its traverse of the neck.  This traumatized all structures in a 6 inch radius in all directions from the path of passage through the neck.  This spread of forces occurred in a fraction of a second, traumatizing all neural structures in the immediate vicinity within a fraction of a second as determined by the speed of the missile according to ballistic studies.
As a result, contraction of the muscles innervated by nerves closest to the bullet's path took place first; -- right deltoid, left deltoid, right biceps followed by the left biceps and sequential contraction of all muscles in the forearms, hands, chest, abdominal walls and paraspinal muscle groups, with muscles in the lower extremities, farthest from the shock wave, responding last.  All neural structures in the neck were stimulated at the same moment…”

3) Some assessments of the Presidents condition from extended film inspections. From the Study Slide 5 video time 0:08:19
My assessment of the film from z226-z254 and z262-z312 was simply that “JFK looked like a statue locked in place”.
ITEK Corporation’s assessment in their report was that “He appeared to remain in a frozen position”.

4) From voluntary neck stiffening seen in sports at stressful times. From the Study Slide 40 or video time 1:35:50
Besides involuntary stiffening that are likely related to a stretch reflex, there can be in some stressful situations some voluntarily stiffening of necks taken like in the sports of soccer and boxing.

I am in total agreement that the shot through JFK's neck causes an almost instantaneous reflex reaction due to the bullet damaging the nerves of the Brachial Plexus. Elsewhere I have posted the following:

The bullet passed between the C7 and T1 vertebrae, close to the spinal column.
This is confirmed by a fracture found in JFK's spine:
“There is an undisplaced fracture of the proximal portion of the right transverse process of T1 (or the region of the costovertebral junction)”

 Quote from the report of the HSCA consulting radiologist, G.M. McDonnel, MD, in: HSCA vol.7: 219.
[see https://www.history-matters.com/archive/jfk/hsca/reportvols/vol7/html/HSCA_Vol7_0115a.htm]

An "undisplaced" fracture is one in which the bones remain aligned indicating a glancing blow by the bullet. This may have affected the trajectory of the bullet through JFK but that is not being considered at this moment. The fracture is of the right transverse process, in accordance with the entry of the bullet slightly to the right of the spine. Looking at this diagram again (obviously the diagram is of the left side of the body but the arguments apply due to the symmetry of the body):



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.

What I did not take into account was the profound effect of "cavitation" as pointed out by Dr Strully:

"This traumatized all structures in a 6 inch radius in all directions from the path of passage through the neck."

The full effect of cavitation is demonstrated in this short video:

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.
So, while I agree that momentary "neck paralysis" appears to have occurred as a result of the shot through the neck, I completely disagree that this paralysis was present at the moment of the headshot. In the clip below we can clearly see that after the initial reaction, during which JFK's elbows extend fully and his body appears to stiffen, his body then relaxes as he slumps to one side and his head drops forward:



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:

There is "very strong evidence against any kind of jet effect"

All I can do is to mention the basis I used for the assessment that there was some jet effect.

1) The modeling overall did a good job of predicting position of the head and upper torso, but there was one place it didn’t respond well and that was between z312 and z313. The model wanted to say that the head position at z313 should have gone even further ahead and taken longer to come back than it did. I struggled with why the heck this was happening, and finally realized that the model did not include any slowing of the head by another force at that time, i.e. some jet effect. Accounting for this corrected that issue.

2) Simply put, typically when you see a noticeable jet, you get some jet effect. There was noticeable jet fan going forward at z313 that I saw, while its net direction may have been a little forward and to the right. A good experiment would be going out in the yard and take a garden hose with a sprayer on the end. With the hose full of water, open the sprayer to provide a noticeable fan and see if you feel zero force pushing back or is there some detectable force pushing back against your hand.

3) Nick Nalli made the most in-depth calculations I have seen on the head shot and concluded there was some jet effect and further estimated some ranges for its effect on the head. I checked and within those ranges there would be enough to correct my model as described in 1) just above.

4) We see a jet in the Z-film but experiments to show head reversal by jet effect are tricky to set up exactly right, and don’t always work, but typically the ones that fail are ones that don’t show much of a jet. This is described some in the examples of the Study on Slide 7 or video time 0:13:39.

"At the moment of impact JFK's chin is resting on his chest (the sternum is a non-issue) JFK's head can be clearly seen being driven into his chest, there is nowhere for it to go so it rebounds.
That this movement is JFK's head being driven into his chest"

When I hold my head at like a 45 degree angle, it is not resting on my chest, but I cannot see his chest directly relative to his chin extent, so can’t comment on this.

"The initial movement at impact is forward"

I agree and both his head and upper torso have initial forward movement.

"The massive crater in the top of JFK's head after impact"

Yes, It looks like the jet exited the top opening going forward.

"The jet effect might work through a small exit hole out of which matter is ejected but it is totally negated by such a massive head wound."

In experiments small exit holes are good for directionally which is important, but they suffer in that they present a much larger pressure drop to overcome to discharge the mass or fast volumetric mass flow out that orifice which is important to the momentum exchange. In fact I think small holes are overall more limiting in this regard as I think it is easier to get directionality out of generous sized hole than large mass flow rates out of a small hole. You commonly see a melon shot with a small exit hole and with a focused but a limited discharge jet and not much movement at all. This is also discussed briefly in the Study on Slide 7 in the video at time 0:13:39.
 
Like I said originally, I would expect there would have been some observation of a mark on chin or chest if such a violent collision happened. Because no one saw a mark does not mean it didn’t happen, but it boils down to just a lack of confirmatory evidence at this point that would prevent me in trying to redefine the whole model base on something I can’t really see, or confirm at this point.

There is an even more counter-intuitive aspect to the headshot than the "back and to the left" movement caused by a shot from behind and that is the nature of the injury to JFK's head. In chapter 16 on his website, Pat Speer explains in detail the nature of this injury, concluding it is what is referred to as a "gutter" or "trench" wound. The bullet enters the head quite high up on the skull and exits just above the hairline. At some point the bullet fragments, either entering or exiting the skull, and some of these fragments pepper the inside of the front of the limo. This would seem to indicate the main injury would be sustained towards the front of the skull (other than a small entrance wound at the rear).
In fact, what happens is that almost the entire top portion of the right side of JFK's head is blown directly upwards, perpendicular to the direction of the bullet transit.
That the top of JFK's head is blown off is evidenced in a number of ways. In the clip below pay particular attention to the shape of JFK's head before the headshot and then to the massive crater that appears in the top of his head immediately after:



The injury is clearly to the top of his head:



The gif below was created by John Mytton and clearly shows the massive injury to the top of JFK's head:



And finally, z313 shows two "jets" exiting the top of JFK's head. The more pronounced "jet" is picked out by the red arrow, the lesser one by the yellow arrow.



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:




Referring back to this clip. At the moment of the headshot there appears to be a fan or spray of material moving forwards:



The cause of this requires a deeper understanding of the mechanics of the head injury.
As the bullet enters and exits the head it tears through the scalp at the back and the front creating weak spots in the integrity of the scalp. It also shatters the skull into numerous small pieces, completely destroying the structural integrity of the skull. As the pieces of skull explode upwards they lacerate the scalp between the two weak spots creating a tear along the top of the head. In the Mytton gif we can see some scalp folded over to the left (as we look at it) but there is no scalp covering the right side of the exposed brain.
This part of the scalp is blown to the right side of the head and is the large, pendulous mass of flesh seen hanging down the side of JFK's head. As this large mass of scalp/skull is blown away it creates the fan of material seen moving forward.

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.

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.

[Jerry Freeman]

A new perspective on “Back and to the Left” in the Z-film...This summarizes the results of an extended study taking a closer look at JFK’s motions....- There was no indication of a frontal shot striking the President

There's nothing 'new' about all that. It appears to be the same old Belin/Ford/Spector blurb.

[Brian Roselle]

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.

[Brian Roselle]

There's nothing 'new' about all that. It appears to be the same old Belin/Ford/Spector blurb.

That's good news if they did the modeling before. I'm curious to know what they had for an omega value for the head/neck from z316 to z324. Do you recall?

Thx

[Jerry Freeman]

The Nicholas Nalli study----
https://www.sciencedirect.com/science/article/pii/S2405844017331882#bbr0060
This statement....

the depiction of a fatal wound to the head caused by a high-powered military rifle bullet, something that ordinary citizens would not have had an inkling about in that era.

....strikes me as rather verbose. What was different about 'that era'? The Dark Ages?
 Mr Nalli makes a statement that is not universally accepted but with which I agree---

a careful comparison between [the] two frames also reveals that President Kennedy's head snaps forward from Z312 to Z313

I have postulated that this just might be because there were two separate strikes to the head. One from behind and one from the right front where many in attendance claim.
Harold Weisberg also thought this...

- The head shot (or shots) remain a puzzzle, but
probably represent two nearly simultaneous impacts, first
from the rear, then from the front.

http://jfk.hood.edu/Collection/Weisberg%20Subject%20Index%20Files/D%20Disk/DeSalles%20Doug%20Jr/Item%2001.pdf
This would agree with earwitness accounts that at that moment the sound was a babam report. Localizing origins would have been astronomical.
Dan Rather viewed a private showing of the Zapruder film shortly after the event. He described it...

After the final shot, the presidents head slumped forward.

A deliberate lie.
I also read thru... https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5934694/
Mr Nalli may know about physics/arithmetic but I don't think he really knows very much about the assassination.

[Dan O'meara]

A few comments and questions only on the parts in question.
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?

I posted:

"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."

I make no mention of "damage" to the Ulnar nerve, only that it is affected by damage to it's root. The reason I postulate this is the unusual "pointing finger" aspect of JFK's, otherwise clenched, hand. I believe this hand position is a signifier of severe nerve damage caused by the bullet's transit through the neck.

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.

Again. I just have to totally disagree with this analysis.
The very extreme initial reaction of JFK's body to the neck shot is obvious.
He straightens up, his elbows fly up to their fullest extent and his body momentarily stiffens. There can be little doubt about that.
But none of this is present by the time of the headshot.
If the paralysis was still present JFK would still be in this extreme position - elbows up, sat rigidly straight. Gravity would have no effect on this. In the clip below we see JFK's fists shoot to his neck area, his elbows fly up and he sits rigidly upright and is "frozen" for an instant. His arms then begin to relax, he looks towards Jackie as his whole body relaxes, he slumps slightly to his left, his arms come fully down and his head slumps forward as his neck relaxes:



To imagine he is in any way still displaying the paralysis of the initial reaction is baffling. There is no component of his initial paralysis present at the moment of the headshot so I find it very difficult to understand how this can be assumed. His body stays in the same position leading up the headshot but this is clearly due to his body being in a relaxed state, not a rigid one.
I guess we'll have to agree to disagree on that.

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.

The bullet entering and exiting the skull creates massive weak spots. The scalp is punctured at both places and the skull itself is shattered into smaller pieces. The cavitation explodes through these weakened areas lacerating the scalp between the two puncture points as it blows the shattered pieces of skull upwards. All structural integrity of the skull is compromised at the moment of cavitation (as is the integrity of the scalp)
We don't need to determine the direction of the bullet from the blowout so I'm not sure how Sturdivan fits into it, to be honest.

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?

Indeed, the white dots are skull fragments being fired into the air by the immense pressures involved. They do not represent any kind of jet effect and if the did it is quite clear that they would provide no backward component to JFK's head movement. In fact, I believe the larger of the "jets" would have a forward component to it. But, as I say, it's not the jet effect, it's material being ejected from the head by the explosive cavitation.
Just to put my cards on the table - I think the Jet Effect hypothesis is one of the most embarrassingly bad pieces of "scholarship" I have ever encountered and I was not surprised to hear that Alvarez, the author of this nonsense, was found out cheating his results.

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.

Agreed.

[Dan O'meara]

The Nicholas Nalli study----
https://www.sciencedirect.com/science/article/pii/S2405844017331882#bbr0060
This statement........strikes me as rather verbose. What was different about 'that era'? The Dark Ages?
 Mr Nalli makes a statement that is not universally accepted but with which I agree---I have postulated that this just might be because there were two separate strikes to the head. One from behind and one from the right front where many in attendance claim.
Harold Weisberg also thought this...http://jfk.hood.edu/Collection/Weisberg%20Subject%20Index%20Files/D%20Disk/DeSalles%20Doug%20Jr/Item%2001.pdf
This would agree with earwitness accounts that at that moment the sound was a babam report. Localizing origins would have been astronomical.
Dan Rather viewed a private showing of the Zapruder film shortly after the event. He described it...A deliberate lie.
I also read thru... https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5934694/
Mr Nalli may know about physics/arithmetic but I don't think he really knows very much about the assassination.

"I have postulated that this just might be because there were two separate strikes to the head."

What was it that led you to postulate this?