The trouble with Nicholas Nalli’s paper on “Gunshot-wound dynamics model’ for JFK assassination


This paper, published in the scientific journal Heliyon, represents an attempt to salvage Professor Luis Alvarez’s model of the gunshot that killed President Kennedy. Alvarez tried to explain the rearward recoil motion of Kennedy’s head, seen in Abraham Zapruder’s film, by what he called a “jetting effect.”

Alvarez experimented by firing bullets into a large class of objects. In all cases but one, photographs showed that a bullet hitting a semi-hard object filled with fluid drove object away from the source of the bullet. Only in the case of melons did Avarez see the desired rearward “jetting effect.” So he ignored the evidence he didn’t like and touted the evidence he did. Sadly for his model, human heads are very different from melons.

Head ShotThe paper proceeds from a key false assumption. This is that the small movement forward of Kennedy’s head (from Zapruder frames Z312 to Z313) is due to the impact of a bullet from the rear.  However, a careful  viewing of the film reveals that the limousine slows dramatically and comes to a virtual or almost complete stop just prior to the impact of the bullet in frame Z313.  It is this deceleration of the limousine that causes a wounded listless Kennedy to continue moving forward relative to the decelerating vehicle and the other unwounded people in the vehicle who are stabilized by their musculature.

Any theory in science, no matter how sophisticated, involved, or advanced must ultimately be tested in the crucible of empiricism.  Any theory that is not consistent with experimental results is quickly discarded.  Any model for the assassination involving a Mannlicher-Carcanno (.26 cal) round impacting Kennedy’s head from behind must address the problem that a round hitting in the middle rear of the skull, as determined by the Warren Commission, would come out his forehead or eye socket as proven in multiple tests conducted by Dr. Alfred Olivier at the Army Ballistics Lab in Aberdeen Maryland, a feature that was not observed.

This predicament caused the House Select Committee on Assassinations to conjecture that the round actually strikes the top right part of Kennedy’s head from the rear and passes through, the last conceivable refuge for the model.   This scenario has two problems.

JFK motorcadeFirst, it’s not consistent with the head wound images on the Zapruder film.  Second, the Discovery channel performed just such a live-fire test using a Mannlicher-Carcanno rifle and an anthropomorphic dummy to represent Kennedy (Inside the Target Car -2008).  The documentary made a point of indicating fragments and debris were driven forward towards the front of the limousine, but there was NO HEAD RECOIL BACKWARDS due to jetting or any other effect.

Nobel Laureate Richard Feynman was fond of saying that “If it disagrees with experiment, it’s wrong.” In that simple statement is the key to science. It doesn’t make any difference how beautiful your guess is, it doesn’t make any difference how smart you are, who made the guess, or what his name is. If it disagrees with experiment, it’s wrong. That’s all there is to it.”

Rush to the knoll

After the gunfire spectators rushed to the grassy knoll where they thought shots had come.

In Nalli’s case, it doesn’t matter how many variables he calculates or considers, or how many computer simulations he runs, because his model doesn’t agree with experiments, it’s wrong.    It isn’t necessary to check his extensive mathematics or analysis because his conclusions are inconsistent with experiments already performed.  Case closed.


In fact, the most direct and straightforward explanation for the rearward motion of Kennedy’s head exhibited in the Zapruder film is that it was simply struck by a projectile from the front right side that remained inside his head causing it to recoil backwards, precisely in the manner of an inverted ballistic pendulum.

Nalli actually mentions the ballistic pendulum multiple times in his paper but somehow fails to make this simple connection, arguing that this scenario for Kennedy  is “physically ruled out,” a conclusion that bears no more relationship to reality than the rest of his paper.

When a ballistic pendulum is struck by a bullet that remains inside the wooden block, it causes the pendulum to recoil back and upwards, the height providing an indication of the initial velocity of the bullet. This is precisely what would happen to Kennedy’s head (in an inverted fashion), if he were struck by a bullet from the front side, which remained inside his head causing it to absorb the recoil momentum of the round and react backwards and to the left.  This would happen if he were struck by a small caliber, (~.22) high speed frangible round.

This is not only the most plausible and straightforward explanation but is also the only explanation consistent with both the laws of physics and the film record.

A Test

This suggests a very simple test.  While the Discovery channel performed such a test firing a large (.30 cal) rifle at the head of an anthropomorphic dummy from the right front side from the actual Grassy Knoll (Inside the Target Car), the high caliber round just punched through the dummy’s head.

However, a small caliber frangible round would remain inside, the dummy’s head would recoil, and the Zapruder film would be readily matched up.   While anthropomorphic dummies and high speed camera’s are not cheap, they are well within the budgets of many technically oriented cable television programs currently in production.

It is indeed striking that after 55 years of documentaries, simulations, and staged reenactments devoted to the Kennedy assassination, not a single one has ever performed this one simple test, motivated by the well-known ballistic pendulum.  This  inexplicable omission, in and of itself, speaks volumes.

One comment

  1. Randy Robertson says:

    Both Chambers and Nalli are wrong. The first bullet came from behind, entered where the autopsy doctors identified an entry wound, fragmented and a fragment went forward and cracked the inner surface of the windshield causing a flare of reflected sunlight on frame 314 as the windshield was deformed from the impact. This proves beyond a doubt that the first bullet DID NOT come from the front. This explosive exit wound was confined to the anterior portion of the right parietal bone and ejected the Weitzman and Harper skull fragments into Dealey Plaza as well as two smaller skull fragments down into the limo. The top rear of the head is undisturbed which would not be the case if the first shot came from the front. A second shot to the head from the front struck the top rear of the head, pushing the head rearward and ejected the Delta skull fragment, bearing a portion of an exit wound onto the trunk of the limo where it was retrieved by Jackie and later taken to the autopsy room where it was x-rayed and examined. The forward and backward movements of the head and the initial ejection of four skull fragments is well documented in the CBS News/Itek study.

    Nalli is wrong because there is evidence for two gunshot wounds to the head by virtue of intersecting fracture lines, Puppe’s Law, being present on the authentic postmortem skull radiographs. An paper describing these findings passed peer review by the Journal of Forensic Science but they declined to publish it, despite having passed peer review because it might initiate ” discussion”. A single shot from behind will not cause the forward and backward movement of the head and can’t cause the delayed rearward ejection of a large piece of skull from the top rear of JFK’s head. The flare of reflected light from the windshield cracking at 314 proves that Chambers is wrong about a single shot from the front.

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