JFK's Head Snap and the Implausible Jet-Effect and Neurospasm Theories

[John Iacoletti]

What force carried to the left? What force carried it upwards, as we see in frame 313? Debris is sent in many directions downrange, to the left, to the right, upward, downward, from what anyone can clearly see in frame 313.

It's a 2D image.  We don't "see" debris traveling to the left.

“Ballistic expert” as in a professional ballistic expert. Who conducts scientific experiments with firearms and various targets. Who conducts these experiments in a systematic manner. Who can give testimony in courts on this technical subject of firearms. These are the ones that I refer to as ballistic experts.
And as far as I know, none of them agree with the CTers on the “impossibility” of the Single Bullet Theory.

You're moving the goalposts.  We were talking about where the Harper fragment was found, not the Single Bullet Fantasy.

[John Iacoletti]

Griffith has a whole website dedicated to arguing that the South was justified in seceding from the Union.

Granted, I haven't clicked on every link, but it purports to give several different viewpoints.

I, on the other hand made a one line joke about Mantik and Fetzer. I guess a one-line joke is the same as writing up a whole website.

Oh, it was a "joke" now.  I see.

Note how reluctant you are to provide a link to my original post. So that others can easily check out your claim. I shall rectify that for you:

https://www.jfkassassinationforum.com/index.php/topic,2622.0.html

Now, my relevant quote:

Is this really a serious charge that BOTH Mantik and Fetzer denied the Holocaust? And BOTH believed that the “Wizard of Oz” portrayed real events? This is equivalent to writing up a whole website on it?

Yeah, that was backpedaling.  Your original statement was "The 'Experts' this book refers to are world renown experts like Dr. James Fetzer and Dr. David Mantik who have discovered that the Holocaust and the Zapruder film are both hoaxes."

[Gerry Down]

Dr. James Fetzer and Dr. David Mantik who have discovered that the Holocaust and the Zapruder film are both hoaxes."

Both have denied the holocaust?

[Tim Nickerson]

Both have denied the holocaust?

That wasn't John Iacoletti's statement.

[Michael T. Griffith]

I didn’t talk about Trump. I talked about your views on the Civil War.

CTers are free to bring up subjects that have nothing to do with the JFK assassination.

Like Gerald Posner plagiarism on articles he wrote that had nothing to do with the assassination. These charges were true. Easy enough for a professional reporter to do. Reporters get their information from what other reporters write. There is simply not enough time for each reporter to conduct their own interviews and write the number of articles demanded of them. And what person who makes the news would be willing or able to give an interview to all the thousands of reporters who want to write about them. But a report is supposed to reword everything, so that everything is in his own worlds. In this ‘Cut and Paste’ world, I would guess Posner ran out of time and published the words of others. This is a technical violation of reporter ethics and he was fired. In any case, CTers make a big deal of this, which has nothing to do with the JFK assassination, and that’s all right.

Or John McAdams being fired for reasons that had nothing to do with his statements on the JFK assassination. But, again, it was alright for CTers to talk about this a lot. Unlike Posner, there was no justified reason for him being fired. The courts ruled that he was fired for political reasons, not because he had done anything unethical.

But, if a LNer talks about the beliefs or actions of CTers, that somehow is off topic.


George McClellan believed that slavery should be allowed to continue. So did Lincoln’s. But by January 1863, Lincoln believed it should not, where McClelland believed slavery should continue, as late as November 1964 and probably until the end of the war. So, I’m not impressed by a defense of McClellan.

But you still believe, as far as I can tell, that the South went to war over the high tariff, and not to protect slavery. This is quite false. These are not the reasons the South was giving in 1861, where they made it clear it was to protect slavery. I don’t know why anyone would ever believe they seceded because of the tariff.

In a nutshell, I believe secession is wrong for two reasons:

1.   It would tend to cause Democracies to split up. Making them more vulnerable to non-Democracies. As Lincoln made clear in his Gettysburg address, the ultimate Union cause was to ensure that the government of the people will not perish from the Earth.

2.   If Secession is a right, then it can be used by the Minority to get what it wants. It turns Democracy on its ear. In the 1850’s Democracy was turned topsy-turvy.
      The South got what it wanted against the wishes of the majority on:

a.   No railway to the west coast, uniting the country – too advantageous to the North.
b.   No Homestead Act – too advantageous to the North
c.   A Low Tariff – wanted by the South
d.   Prevent the establishment of the “Land Grant Colleges” – not wanted by the South.

The South, the minority, was getting all sorts of things they wanted, all through the threat of Secession. Many of which had seemingly nothing to do with slavery.

Once the South seceded, and secession was no longer a threat, in 1862, the majority finally got what it wanted. The building of the Transcontinental railroad. The college land grands, which started colleges, like the University of California, among others. These colleges were the key to allowing America to becoming a real-world leader in Science in the twentieth century. It has been argued that the high tariffs were the key to getting industry established in America, because, initially, they could not compete with Europe. But once allowed to get established, they could more than compete against Europe, even on a level playing field.

In any case, right or wrong, the majority should get what it wants, not the minority. The threat of secession turns this on its head.

By the way, in 1861, Congress did raise the tariffs. But this happened after the 7 states seceded. And the other 4 seceded not because of the high tariff but because of the attack on Fort Sumter, Lincoln’s call on them to supply troops, and the likely necessary for Union armies to pass through them, as they did through Pennsylvania, and indeed all northern states. High tariffs did not cause secession. Secession caused the high tariffs.

Some of your arguments are valid. Some of them are erroneous. And some of them are overly simplistic. As just one example, McClellan was very anti-slavery, but he was also a constitutionalist. He was perfectly okay with ending slavery as long as it was ended constitutionally. As long as slavery was legal, he did not feel authorized to use extra-legal means to free slaves, but he personally detested slavery.

[Joe Elliott]

Some of your arguments are valid. Some of them are erroneous. And some of them are overly simplistic. As just one example, McClellan was very anti-slavery, but he was also a constitutionalist. He was perfectly okay with ending slavery as long as it was ended constitutionally. As long as slavery was legal, he did not feel authorized to use extra-legal means to free slaves, but he personally detested slavery.

My arguments are true. In 1861, the Southern stated they seceded in order to maintain slavery. Four of the seceding states stated their reasons in their “Declaration of Causes” official statements, emulating the 1776 “Declaration of Independence”.

https://www.battlefields.org/learn/articles/declarations-causes

There are many complaints about the Northern threat to the institution of slavery. And many complaints about Northern states exercising their own “State Rights” and passing laws that conflict with Federal Law, the “Fugitive Slave Act” of 1850.

But not once is the word ‘Tariff’ mentioned.

I assume the 7 other seceding states would have issued similar statements, but were too busy, or maybe deep down too ashamed to express their base motives in an official declaration.


It was only after 1865 that the south started to come out with “Declaration of Causes”, Version 2.0, which now gave more noble reasons for Secession. To protect States Rights. To avoid high tariffs. And slavery was a more minor issue. And until recently, these were the reasons taught in our schools. And is still being pushed by some people.



McClellan detested slavery. So did a lot of people, in both the North and South, who thought slavery should continue, as did McClellan. So, again, I am not impressed with McClellan’s views. And slavery was ended permanently though constitutional means so why should anyone complain?

[Michael T. Griffith]

Below is one of Dr. Art Snyder’s critiques of the jet-effect and neuromuscular-reaction theories. Dr. Snyder is a former physicist at Stanford University. He received his PhD in physics from the University of Illinois. He taught physics at Indiana University before joining the staff at Stanford University. Dr. Snyder wrote this critique in 1998 in response to Gerald Posner’s arguments about JFK’s head snap in Case Closed:

The head snap refers to the backward motion of President Kennedy’s head seen in the Zapruder film. As Posner puts it, “But if the President was struck in the head by a bullet fired from the rear, then why does he jerk so violently backward on the Zapruder film which recorded the assassination? To most people, the rapid backward movement at the moment of the shot means the President was struck from the front.” Posner begins by trying to dismiss the significance of the head snap with a quote from respected forensic pathologist Dr. Michael Baden: “People have no conception of how real life works with bullet wounds. It’s not like Hollywood, where someone gets shot and falls over backwards.” Dr. Baden is right about people, but heads are more than an order of magnitude lighter than a person. The velocity imparted to a head by a stopping bullet is given by conservation of momentum:

V head = V bullet (M bullet/M head)

where V is velocity and M is mass. For a 10 gm bullet moving at 550 meter/sec hitting a 5 kg head, this is -1 meter sec, or to put it another way ~2.4 inches per Zapruder frame.

Having used Dr. Baden to dismiss the possibility that a bullet strike could cause head motion, Posner twists around and in the next paragraph notes that Itek Corporation, using a “computer enhancement” (Itek, 1975), discovered that JFK “first jerked forward 2.3 inches before starting his rapid movement backward.” Itek did not “discover” this forward motion. Cal-Tech physicist Richard Feynman noticed it in 1966 when David Lifton showed him the Zapruder frames published in Life (Lifton, 1980, 48). Warren critic Josiah Thompson published measurements made on black and white copies in the 1967 book Six Seconds in Dallas (Thompson, 1967, 90).

The measurements of Itek and Thompson are almost inconsistent with a shot from a Mannlicher-Carcano. The motion is so large that nearly all the momentum of the bullet is needed to account for it. However, quantitatively Thompson and Itek were mistaken. The apparent motion between Zapruder frames Z312 and Z313 is an artifact of the blurring of frame Z313. This is not to say that JFK’s head did not move forward between frames Z312 and Z313, but that the Z313 blur obscures the motion so that it cannot be measured using these frames. The actual forward motion (~0.3 meter/sec) can be estimated by comparing Z312 to Z314. It is about 1/3 the value obtained using the Itek or Thompson measurements—consistent with a Carcano bullet imparting ~1/3 its momentum and ~1/2 its energy.

What is the purpose of Posner’s dance around the forward motion? He trots out Dr. Baden to deny that the direction of motion tells us anything, then uses the observed forward motion to verify a shot from the rear. None of this explains why the head went backward ~100 msec later.

An explanation for the backward proposed by Nobel Laurette Luis Alvarez, in his 1976 article in the American Journal of Physics. Posner’s description of Alvarez’s work is ludicrous:

“Dubbed the ‘jet effect,’ Alvarez established it both through physical experiments that recreated the head shot and extensive laboratory calculations. He found when the brain and blood tissue exploded out of JFK’s head, they carried more momentum than was brought in by the bullet—in an opposite direction—as a rocket does when its jet fuel is ejected.”

The “recreation” of the head shot consisted of shooting 2-3 pound melons wrapped in strapping tape with the wrong gun (30.06) and the wrong ammunition (hunting instead of jacketed military ammunition). The “extensive laboratory calculations” consisted of a “back of the envelope calculation” Alvarez did in his hotel room at the 1969 meeting of the American Physical Society in St. Louis (Alvarez, 1976, 819). The calculation demonstrates that the jet-effect is kinematically allowed. It does not establish that ejected material “carried more momentum than was brought in by the bullet,” but only that this is possible.

The possibility of the jet-effect arises from the relationship between kinetic energy and momentum:

P=/2ME

Where P is momentum, M is mass and E is kinetic energy. If a large enough mass is ejected, it can carry more momentum than the income bullet deposits using only a fraction of the bullet’s energy. For example, if 0.2 kg of material were expelled carrying 10% of the bullet’s energy, it would carry a 7.8 kg-m/sec of momentum—enough to overcome the maximum possible momentum a Carcano bullet can deposit (6 kg-m/sec). Kinematics allows jet-effect to occur but only the detailed interaction of the bullet with the target determines if it actually occurs under a given set of circumstances.

Alvarez’s melon shooting experiment demonstrated that there are circumstances under which the jet-effect occurs. Dr. J.K. Lattimer (1980) did experiments using the correct rifle and ammunition. Lattimer claimed his targets—whether skulls or melons—“always” went backwards. Edgewood Arsenal did experiments on skulls (Edgewood 1964; HSCA, Vol. 1, 404). All skulls shot by Edgewood moved away from the shooter [i.e., they moved in the same direction the bullet was traveling].

Since the publication of Case Closed, there have been by Dr. Doug DeSalles and Dick Hobbs (DeSalles and Hobbs, 1994) and by us (Snyder, 1996). DeSalles and Hobbs shot tape-wrapped melons using a Carcano rifle and jacketed ammunition. In 11 shots they saw no jet-effect. In 1996 we undertook the resolve the apparent discrepancy. We shot a variety of melons with two different guns (30.06 and Carcano) and both jacketed and soft-nosed hunting ammunition. The results were surprisingly simple: Hunting bullets produced a jet-effect. Jacketed bullets did not produce a jet-effect. . . .

In his explanation of the head snap, Posner employs, in addition to the jet-effect, a so-called “neuromuscular spasm.” His full explanation might be described as jet-assisted neuromuscular spasm. Posner writes, “First, when the bullet destroyed the President’s cortex, it caused a neuromuscular spasm, which sent a massive discharge of neurological impulses from the injured brain down the spine to every muscle in the body.”

The authority for this statement is the House Select Committee on Assassinations forensic pathology panel. The HSCA is not as definite as Posner: “The panel further recognizes the possibility of the body stiffening, with an upward and backward lunge, which might have resulted from a massive downward rush of neurologic stimuli to all efferent nerves” (HSCA, 1979, 174-175).

The HSCA also suggested that “decerebrate rigidity” or DR as described by Sherrington (1898) “could contribute to the President’s backward motion.” No practicing neurologist or neuro-scientist testified that DR or a “massive downward rush of neurologic stimuli” could explain the head snap. DR is due to the absence of nerve signals that keep opposed muscles in equilibrium rather than “a massive discharge of neurologic impulses.” Since JFK is positioned facing to the left at the moment of the fatal head shot, any “upward and backward lunge,” whatever its cause, would have pushed JFK to the right, not the left.

The HSCA also noticed that “such decerebrate rigidity as Sherrington described usually does not commence for several minutes after separation of the upper brain centers from the brain stem and spinal cord,” but included DR in their stew of possibilities anyway (HSCA, Vol. 7, 174). (“Case Open: Skepticism and the Assassination of JFK,” Skeptic, volume 6, number 4, 1998, pp. 52-54. NOTE: I was unable to duplicate some of the math symbols, so I used to closest approximation that my keyboard offered.)

[Joe Elliott]

Below is one of Dr. Art Snyder’s critiques of the jet-effect and neuromuscular-reaction theories. Dr. Snyder is a former physicist at Stanford University. He received his PhD in physics from the University of Illinois. He taught physics at Indiana University before joining the staff at Stanford University. Dr. Snyder wrote this critique in 1998 in response to Gerald Posner’s arguments about JFK’s head snap in Case Closed:

. . .
The measurements of Itek and Thompson are almost inconsistent with a shot from a Mannlicher-Carcano. The motion is so large that nearly all the momentum of the bullet is needed to account for it. However, quantitatively Thompson and Itek were mistaken. The apparent motion between Zapruder frames Z312 and Z313 is an artifact of the blurring of frame Z313. This is not to say that JFK’s head did not move forward between frames Z312 and Z313, but that the Z313 blur obscures the motion so that it cannot be measured using these frames. The actual forward motion (~0.3 meter/sec) can be estimated by comparing Z313 to Z314. It is about 1/3 the value obtained using the Itek or Thompson measurements—consistent with a Carcano bullet imparting ~1/3 its momentum and ~1/2 its energy.
. . .

Dr. Snyder’s analysis is illogical. He claims that frame z313 is too blurry to get an accurate measure of how much the head moved forward between z312 and the blurry z313. Dr. Snyder’s solution? Compare the blurry z313 with z314.

If I may help out the confused Dr. Snyder, I think he meant to say that one should compare the non-blurry z312 with the non-blurry z314. I don’t know if this is necessary, but at least it’s a logical idea.


In addition, Dr. Snyder is just flat wrong that the WCC/MC bullet needs nearly all its momentum to push the head the amount reported by Itek.

I found some estimates of the mass of the human head as being 8 pounds, about 4 kilograms. I decided to make my own estimates. And I am sorry to report to the CTers of this forum that I did not do this by cutting my own head off but by measuring the circumference of my head. Both horizontally and vertically (over the top and under the chin). Assuming the same density of water (perhaps the density of bone is balanced by the sinuses) I came up with an estimate of 4.6 kilograms.

Doing some calculations, I find that moving a 4.6-kilogram mass forward with the momentum of a WCC/MC bullet going 1900 f/s, gives a calculated velocity of 1.3 meters per second. The observed Itek motion (which I recall was 2.1 inches) was 0.98 meters per second. So only about 75% of the momentum is needed, according to these calculations.

Further, there is no need to assume the entire head moved forward 2.1 inches. More likely, the head rotated forward, with the upper part of the head moving forward about 2.1 inches, and the lower part less.

All and all, by a rough estimate, only about half the momentum of the bullet is needed to move the head the observed amount in 55 milliseconds. This is inline with Ballistic Expert Larry Sturdivan’s estimate.

In actual truth, a WCC/MC bullet does have enough momentum to move JFK’s head forward about 2 inches in 55 milliseconds and still have enough momentum for its fragments to crack the windshield, dent the windshield frame, and slightly wound Mr. Tague. It is curious that the calculations are consistent with this hypothesis, as if this is exactly what happened.


By the way, my estimates and calculations:

•   Rough circumference of the head 60 to 70 cm, call it 65 cm.
•   Using the calculations for a sphere, volume of the head 4,600 cubic centimeters
•   Mass of the head 4.6 kilograms
•   Mass of the bullet 161 grains or 10.4 grams
•   Velocity of the bullet, 1900 f/s or 579 meters per second
•   Calculated velocity of the head after having 100% of the bullet’s momentum transferred, 1.31 meters per second
•   Observed velocity of the head in the Itek study, a movement of 2.1 inches in 55 milliseconds, or 0.98 meters per second

And this does not account for the head nodding forward, and not having the entire head move a full 2.1 inches forward.


And by the way, I would expect a real professional physicist to provide the basis of his calculations, as I did (a former high school physics student), like the estimated mass of the head, mass of the bullet, velocity of the bullet, calculated velocity of the head and the observed velocity of the head, and not just state “almost all the momentum is required”, with no numbers to back him up. Perhaps Dr. Snyder was having an off day.