I’ve been saving this, and perhaps now is the time to share it, because it is the best demolition of the neuromuscular-reaction theory I have read; it is also a good refutation of the jet-effect theory (although even better ones have been done by Dr. Chambers, Dr. Mantik, and Dr. Snyder). This is from a rebuttal essay written by Dr. Gary Aguilar (MD) and Dr. Cyril Wecht (MD, LLB) titled “The Science Behind the Persistence of Skepticism in the JFK Case” and published in the Spring 2016 edition of the
Association of Firearm and Toolmark Examiners (AFTE) Journal.
Aguilar and Wecht wrote in response to claims made earlier in the journal by Lucien and Michael Haag and Larry Sturdivan. One of the subjects that Aguilar and Wecht discussed was JFK’s backward head movement and the two lone-gunman theories regarding that movement: the neuromuscular-reaction theory and the jet-effect theory. You will notice that Aguilar and Wecht (who is a forensic pathologist) endorse Dr. Donald Thomas’s critique of Sturdivan’s defense of the neurospasms theory. I quote from the section of their essay on JFK’s backward head movement (note: the essay is heavily footnoted, but I’ve removed the footnotes for ease of reading):
Both Mr. Haag and Mr. Sturdivan argue that either a “jet effect” caused by a shot from behind, or a “neuromuscular reaction,” caused the President’s rearward head motion after Zapruder frame 313. Both scoff that a grassy knoll shot might explain it. Because JFK’s reaction to the fatal shot is perhaps the most important and contentious issue raised by Messrs’ Haag and Mr. Sturdivan, the topic deserves a detailed discussion.
As for what Mr. Haag has called the “Newtonian physics” explanation for Kennedy’s rearward jolt - Luis Alvarez’s so-called “jet effect” - Mr. Haag would have done well to ask his colleague about the Nobel Laurate’s conclusion. “The question is,” Mr. Larry Sturdivan has written, “Did the gunshot produce enough force in expelling the material from Kennedy’s head to throw his body backward into the limousine? Based on the high-speed movies of the skull shot simulations at the Biophysics Laboratory, the answer is no.”
Readers should pay more attention to Dr. Alvarez’s published claims than his credentials. (Just as he had “proved” what the government preferred - that a jet effect from Oswald’s shot had swung JFK backward, Dr. Alvarez also once said that he had “proved” what the U.S. and Israeli government falsely claimed was true: that there had been no South African/Israeli nuclear test in the Indian Ocean – the politically sensitive, so-called “Vela Incident.” Dr. Alvarez’s claim was subsequently shredded by private, government and military investigators.)
Re JFK, in the prestigious American Journal of Physics Dr. Alvarez wrote, ““It is important to stress the fact that a taped melon was our a priori best mock-up of a head, and it showed retrograde recoil in the first test … If we had used the ‘Edison Test,’ and shot at a large collection of objects, and finally found one which gave retrograde recoil, then our firing experiments could reasonably be criticized. But as the tests were actually conducted, I believe they show it is most probable that the shot in 313 came from behind the car.”
First, surely AFTE members do not live in a universe in which a soft-shelled melon, even a tape-wrapped one, is the “best mock-up” of a bony human skull, particularly when said melon weighs about half what a human head weighs. Second, it was no less than Warren loyalist John Lattimer, MD who revealed that, apparently unable to get Mr. Haag’s preferred “Newtonian explanation” using jacketed Mannlicher Carcano bullets, Dr. Alvarez instead shot soft-nosed, .30-06 rounds. But not just any old .30-06 rounds, with their ~2800 ft/second muzzle velocity; he “hot-loaded” his cartridges to 3000 ft/sec, and only then got his famous “jet effect.” Worse, Dr. Alvarez withheld key information about his tests.
Dr. Josiah Thompson was recently given access to the photo file of the shooting tests by one of Dr. Alvarez’s former graduate students, Paul Hoch, Ph.D. It turns out that the Alvarez team shot at lots of targets – coconuts, pineapples, water-filled jugs, etc. The only objects that demonstrated recoil were his “a priori best mock-up of a head,” the disanalogous melons. AFTE readers are invited to scour Dr. Alvarez’s paper, which we’ve linked to, for his mentioning anywhere these other, inconvenient shooting results. We won’t insult the intelligence of AFTE readers by recounting what happened when Alvarez’s team shot targets that were more analogous to skulls: coconuts.
Finally, Mr. Haag proffers John Lattimer, MD’s skull-shooting tests as proof of the jet effect that his own colleague from Edgewood had disproved and dismissed. Using a Mannlicher Carcano and firing downward at filled human skulls perched atop ladders, Dr. Lattimer’s skulls recoiled. In his book, Hear No Evil, Donald Thomas, Ph.D. explained why: “Lattimer’s diagrams reveal that the incoming angle of the bullet trajectory sloped downwards relative to the top of the ladder, with the justification that the assassin was shooting from an elevated position … But the downward angle would have had the effect of driving the skulls against the top of the ladder with a predictable result – a rebound.” (A video clip of Dr. Lattimer’s shooting tests shows the ladder rocking forward as the skull is driven against the top of the ladder.)
Clearly, the forward momentum Mr. Sturdivan had shown pushing his test skulls forward was what was being transmitted to the ladder, causing it to move forward while the skull rebounded. Unlike Dr. Lattimer’s skulls, the base of JFK’s skull and his chin were not resting on a hard, flat surface. (It is also worth mention that the “wounds” sustained by the blasted skulls were not, as Dr. Lattimer reported, “very similar to those of the President.”)
The results of Dr. Lattimer’s tests are in sharp contrast not only to those Mr. Sturdivan reported from the Biophysics Lab, but also to similar, skull-shooting tests conducted by University of Kansas’s pathology professor, Dr. John Nichols, MD, Ph.D., F.A.C.P. Rather than shooting down at skulls perched atop a flat surface, Dr. Nichols shot WCC ammo at both melons and cadaver material that were suspended by a wire. (Warren loyalist Paul Hoch, Ph.D. has said that this was the proper way to test for “jet effect” - personal communication.) Professor Nichols’ finding? “This study did not demonstrate the jet effect and would lead us to reject the jet effect as the basis for President Kennedy’s backward head movement.”
Inasmuch as Dr. Lattimer achieved such different results than Edgewood Arsenal and Dr. Nichols, Dr. Thomas observed, “this obvious difference in design would appear to be the explanation for the stark difference in the results.” Dr. Thomas also pointed out that, “Lattimer’s photographs of skulls do not show a jet plume. Instead they show a Kronlein Schuss effect with a blowout of material through the top of the skull. Lattimer did not achieve jet effect.”
JFK’s Rearward Lunge and Neuromuscular Reaction
Inasmuch as Dr. Thomas, Dr. Nichols, and Mr. Sturdivan are surely right that “jet effect” cannot explain Kennedy’s lunge, the only explanation Mr. Haag and Mr. Sturdivan have left that leaves Oswald standing in the dock is some variant of a neurological spasm, or as Mr. Sturdivan, who has no credentials in medicine, neurophysiology, etc., described it to the House Select Committee, a “neuromuscular reaction.” Without suppling a citation, as per his custom, Mr. Sturdivan writes in his riposte that “Dr. Michael Carey calls (JFK’s motion) a ‘decerebrate reaction. Look it up.’” We did look it up, if only to confirm what we already knew. We invite AFTE readers to do the same. We also looked up the fact that Mr. Sturdivan has elsewhere described JFK’s movement as a “decorticate reaction,” as if the two reactions were the same thing. Setting aside the fact they are not, JFK’s motions are neither.
In decorticate posturing the patient’s back arches backwards, the legs extend and the arms flex inward. In decerebrate posturing the patient’s back arches and the legs extend (as they do in decorticate posturing), but the arms extend out parallel to the body. If one compares his posture at Zapruder frame 230, or in any frame after the back shot but before the head shot, JFK’s arms are flexed inward toward his neck, reacting to the first shot. In the frames following the head shot, JFK’s head moves backward but his back does not arch; JFK’s legs do not extend. Nor do his arms flex or extend, but fall limply toward his lap as his upper, probably paralyzed, body follows his blasted cranium rearward.
Furthermore, in the frames following frame 327, 7/10ths seconds after the head shot, JFK’s head starts moving forward, his back then follows forward, too, but at a slower rate than his cranium, which moves forward at as fast a rate, or faster, than his head lunges backward after Zapruder frame 313. It thus “flexed” forward the same way it had “extended” backward: Kennedy’s back followed JFK’s head as it abruptly rocked forward. At no time did Kennedy’s back arch backward, nor did his legs extend, the basic requirements of decorticate and decerebrate posturing.
From the web, below are images contrasting decerebrate and decorticate posturing [click the essay’s URL at end of this quote to see the images]. JFK assumed neither posture in reaction to the head shot.
Decorticate posture results from damage to one or both corticospinal tracks. The upper arms are adducted and the forearms flexed, with the wrists and fingers flexed on the Decerebrate posture results from damage to the upper brain stem. The upper arms are adducted and the forearms arms are extended, with the wrists pronated and the fingers flexed. The legs are stiffly extended, with plantar flexion of the feet.
Can Momentum Transfer From a Grassy Knoll Shot Explain JFK’s Rearward Jolt?
Given that the President’s motions are neither decorticate nor decerebrate reactions, and given that a “jet effect” cannot explain them, what then of the possibility momentum transfer from a grassy knoll shot explains JFK’s backward snap?
In considering this option, we will use Mr. Sturdivan’s own work, a man with whom we do not always disagree. We agree with the testimony he gave concerning the skull-shooting tests conducted by Army’s Biophysics Lab that the House Select Committee. “All 10 of the skulls that we shot did essentially the same thing,” Mr. Sturdivan swore, “They gained a little bit of momentum consistent with one or a little better foot-per-second velocity that would have been imparted by the bullet … .” (They saw no recoil from a “jet effect.”) Since jacketed bullets deliver momentum to skulls, it’s likely that skulls struck with soft-nosed, non-jacketed hunting rounds that flatten on impact would impart even more. We also agree with Mr. Sturdivan that “a similar explosion would have taken place if the bullet had gone through in the opposite direction” – from, say, a tangential shot from the right front. However we disagree with the faulty scientific premises Mr. Sturdivan used to argue that a shot from the right front could not have deposited sufficient rearward momentum to move JFK backward.
While referring to his momentum calculations derived from the skull shooting tests, he testified, “As we can see from the chart, this velocity of 1.2 feet per second is not the kind of velocity that would throw the President bodily around backwards, forwards, or in any direction no matter which direction the bullet came from. The deposit of momentum from the bullet is not sufficient to cause any dramatic movement in any direction.” (In his book, Mr. Sturdivan reported a higher velocity: “the (test) skull … moves forward at approximately 3 feet/sec, just as it must from the momentum deposited by the bullet.”) Mr. Sturdivan thus argued, as he testified, that a shot from behind would have caused “slight movement toward the front, which would very rapidly be damped by the connection of the neck with the body.” We will address two issues here.
First, it was author Josiah Thompson, Ph.D. who was the first to claim that the Zapruder film revealed that JFK’s head moved fleetingly forward between the clear frame 312 and the very blurred frame 313. However, additional studies done during the past several years have convinced Dr. Thompson and others that smear artifact in frame 313 gives the impression of forward motion that is uncertain and may be illusory. Second, Mr. Sturdivan’s conclusion that momentum transfer could not explain JFK’s skull motion was based on experiments using modestly powered Mannlicher Carcano rounds weighing 162 grains (0.023 lbs) that were fired from a distance of 90 yards. And he assumed the fatal bullet deposited half of its momentum when it struck Kennedy’s 15 pound skull. These assumptions are unreasonable, and they stack the deck. (For starters, why assume a grassy knoll gunman would use a Mannlicher Carcano?)
In his book, Hear No Evil, Don Thomas, Ph.D. has dissected Mr. Sturdivan’s analysis in considerable detail. With permission, we quote Dr. Thomas in extenso.
Mr. Sturdivan’s calculation, Dr. Thomas notes, was “derived indirectly from his tests shooting human skulls with a Mannlicher-Carcano. The bullet’s velocity at a distance of 90 yards was 1600 feet per second according to Sturdivan (in fact, the Army’s data indicated a value closer to 1800 fps) (sic). Sturdivan then divided this number in half on the supposition (unstated) (sic) that the bullet would deposit only half of its momentum. This supposition was apparently based on his observation that a velocity of something like ‘one foot-per-second’ was imparted to test skulls when shot with the Carcano. Somehow, Mr. Sturdivan managed to miss the point that the rearward movement might have involved a shot origination from the grassy knoll only 30 yards in front of the target, with consequently less loss of velocity from air resistance, than from a position 90 yards behind the President. It also seemed not to have occurred to Sturdivan that the President might have been shot from the grassy knoll with a different rifle than the modestly powered Mannlicher-Carcano….
“For the purposes of this discussion let us suppose that the hypothetical killer on the grassy knoll was armed with a .30-.30 rifle … (which) happens to have a muzzle velocity (2200 ft/ sec) very close to that of the Carcano, and fires a 170 grain bullet, slightly larger than the Carcano bullet. At 30 yards the projectile would have struck at a velocity of approximately 2100 fps … the momentum on impact with the head would be 50 ft-lb/sec. If one postulates a hunting bullet (in accordance with the X-ray evidence) (sic) which is designed to mushroom and deposit its energy at the wound instead of a fully jacketed bullet, we will allow a deposit of 80% of the momentum, leaving a residual velocity for the exiting bullet. This results in a momentum applied to the target of 40 ft-lb/sec; considerably more than Sturdivan’s stingy allowance of 18.4 ft-lb/sec.
“It is important to realize that at the time Kennedy was struck with the fatal shot at Z-312-3, he had most likely been paralyzed by the shot through the base of the neck (as Mr. Sturdivan admits). Consequently, his head was lolling forward, not supported by the muscles of the neck. This fact tends to minimize the damping effect (that so troubled Mr. Sturdivan) from the absorption of shock by the neck until after the head has snapped back. Assuming a head weight of 12 lbs, the velocity imparted to the head would be approximately 3.3 feet per second … .” (The same speed of the test skulls that Mr. Sturdivan reported in his book, though in JFK’s case it might have even been faster as most estimates put the weight of a human head at 10-11 lbs.)
From the study of the Zapruder film by Josiah Thompson, the observed rearward velocity for the head was roughly 1.6 feet per second after frame 313.
If Mr. Sturdivan is right that jacketed, Western Cartridge Company (WCC) shells moved blasted skulls forward at 3 ft/ sec, imagine how much faster skulls would move if hit with heavier, higher velocity, soft-nosed bullets; perhaps enough not only to move JFK’s skull “back to the left,” but also enough to even nudge his paralyzed upper body backward.
Mr. Haag argued that a “’synchronized’ or concurrent arrival of two bullets (one from the rear and one from the right front) is critical to nearly all conspiracy advocates’ claim of a second shooter.” Although Dr. Wecht has suggested this possibility in the past because of what was then accepted, as our understanding has matured, so has our interpretation of the events in Dealey Plaza. There need not have been two, near-simultaneous shots circa Zapruder 313. It’s more likely that there was just one – fired from the right front, striking tangentially near the top right portion of the President’s skull, with a portion of the bullet being deflected upward and to the left-rear of the limousine. The possibility that a second head shot struck from behind circa Z-327 is a tantalizing possibility, for it would explain why the President’s head swiftly rolled forward after that frame, at a time Mr. Sturdivan believes his “decorticate” or “decerebrate” “neuromuscular reaction” should have had him arching backward. (https://kennedysandking.com/images/pdf/AguilarWechtAFTA2016.pdf)
