A critical look at Luis Alvarez’s jet effect explanation for the head movement of John Kennedy when he was assassinated on November 22, 1963

by Tony Szamboti, mechanical engineer

In his article published in the September 1976 issue of the American Journal of Physics, Dr. Luis Alvarez claimed that he was pushed by a graduate student of his (Paul Hoch) to develop his explanation for what he calls “the odd behavior” of President John F. Kennedy’s head (as seen in the Zapruder film) when he was assassinated in Dallas, Texas on November 22, 1963. For the convenience of the reader the meat of the article, where Dr. Alvarez espouses his theory and shows all of his calculations for what he calls a “jet effect”, is shown in the paragraphs below. The paragraphs are shown in the order in which they appeared and the wording is verbatim from his article. The full article, which also covers his analysis for determining the number and timing of the shots, an explanation for the deceleration of the limousine, and the speed of Abraham Zapruder’s camera, can be found at any large public library by asking for the September 1976 issue of the American Journal of Physics.

My critique is of his “jet effect” explanation for the rearward head snap and follows the portion of his article shown.

Dr. Luis Alvarez’s jet effect explanation of John Kennedy’s rearward head movement being possible when allegedly shot from the rear

Paul Hoch often pressed me for an explanation of the odd behavior of the President’s head, and although I hadn’t observed it myself, I usually suggested that the head had probably been held erect by muscles controlled by the brain, and that when the controls were suddenly damaged, the head fell back. I was finally convinced that this explanation was incorrect after Paul Hoch handed me a copy of Thompson’s book as I was leaving Berkeley for the February 1969 meeting of the American Physical Society in St. Louis. On the plane I had time to study the book carefully. It is beautifully printed, with excellent photographs and carefully prepared graphs. When I studied the graph showing the changing position of the President’s head relative to the moving car’s coordinate system, I was finally convinced that the assassination buffs were right; there had to be a real explanation of the fact that the President’s head did not fall back, but was driven back by some real force.

And the answer turned out to be simpler than I had expected. I solved the problem (to my own satisfaction, and in a one-dimensional fashion) on the back of an envelope, as I sat in solitary splendor in the beautiful suite that the St. Louis hotel management supplied me in my capacity as president of the APS.

I concluded that the retrograde motion of the President’s head, in response to the rifle bullet shot, is consistent with the law of conservation of momentum, if one pays attention to the conservation of energy as well, and includes the momentum of all the material in the problem. The simplest way to see where I differ from most of the critics is to note that they treat the problem as though it involved only two interacting masses: the bullet and the head. My analysis involves three interacting masses, the bullet, the jet of brain matter observable in frame 313, and the remaining part of the head. It will turn out that the jet can carry forward more momentum than was brought in by the bullet, and the head recoils backward, as a rocket recoils when its jet fuel is ejected. (Col. William H. Hanson came to the same conclusion, independently.)

If a block of wood is suspended by strings from the ceiling, it is called a ballistic pendulum, and physicists or gunsmiths can calculate the velocity of a bullet shot into it to be

v_B = v_WM_W/M_B,(1)

where v_W is the velocity of the wooden block after it stops the bullet, M_W and M_B are the masses of the wooden block and bullet. Equation (1) follows directly from the law of conservation of momentum:

v_BM_B = v_WM_W. (2)

In using a ballistic pendulum, we normally forget that the collision of the bullet and wooden block is very inelastic. Of the incoming kinetic energy of the bullet, only a small fraction appears as kinetic energy of the moving wooden block; the remaining fraction (1 – f) goes into heating the wood. If M_B << M_W,

KE_W = f(KE_B),

M_Wv_W²/2 = f x M_Bv_B²/2. (3)

From (3) and (2),

f = M_B/M_W(4)

For the case of a 10-g bullet, and a block weighing 10 kg, it can be seen that 99.9% of the incoming kinetic energy goes into heating the block, and only 0.1% appears as mechanical energy. Ballistic pendulums are designed so that they contain the inelastically dissipated energy. Unfortunately, the human head is not able to contain the major fraction of the energy carried in by the bullet. This tragic aspect of the assassination is clearly visible in frame 313 of the Zapruder film, and is discussed in detail in the reports of the autopsy surgeons.

The mechanism of the retrograde recoil turns out to be rather simple, if one remembers that 99.9% of the incoming energy must be accounted for. The momentum associated with a given amount of kinetic energy varies as the square root of the mass of the object carrying that kinetic energy:

p = (2MK)^1/2 (5)

where p is the momentum, and K is the kinetic energy of the object with a mass M.

Figure 4 shows what happened when my friends and I fired bullets at melons that had been wrapped with Scotch glass filament tape, to mock up the tensile strength of the cranium. Under the influence of the bullet, some of the material making up the melon breaks through the reinforcement, and carries momentum in the forward direction. (Frame 313 of the Zapruder film shows this same phenomenon.) As we shall now see, the momentum carried forward in this way can be much larger than the momentum brought in by the bullet. For example, if the bullet weighed 0.1% of the melon weight, and if 10% of the incoming kinetic energy was used to propel 10% of the mass of the melon forward, then the momentum of the jet expelled forward would be (10)^1/2 times that of the incoming bullet. (I will use subscripts, b for bullet, j for forward moving jet, and m for melon.)

P_j = (2M_jK_j)^1/2 = (2 x 100M_b x 0.1K_b)^1/2

= (10)^1/2 (2M_bK_b)^1/2 = (10)^1/2p_b(6)

since = M_j= 0.1M_m 100M_b, K_j= 0.1K_b. The melon would then recoil backward with about twice the velocity it would have been expected to go forward, assuming it were made of wood. This is because the melon, acting at first as a ballistic pendulum, acquires a forward velocity equal to v_m|BP = p_b / M_m. (The notation v_m|BP means the velocity one would expect the melon to have if it contained all the kinetic energy of the bullet, as a ballistic pendulum does.) But in the center of mass of the system of the melon, which is moving “forward” with the expected velocity, a jet moves forward with momentum equal to (10)^1/2p_b---as we have just seen. It gives the melon an equal and opposite momentum, in the moving (CM) system; in that system, p_m = -(10)^1/2p_b. If we neglect the 10% loss of the mass by the melon to the jet, the recoil velocity of the melon (in the CM system) is -(10)^1/2 times the expected value. Since velocities add vectorially, the final velocity of the melon (in the laboratory system) is [1- (10)^1/2]v_m|BP. Since the square root of 10 is close to 3.16, the observed velocity of the melon is about –2v_m|BP.

If one wants to know more about the details of the transfer mechanism of kinetic energy from the bullet to kinetic energy of the fragments thrown forward, he will have to ask someone more knowledgeable in the theory of fluid mechanics than I am. My intuitive feeling is that the conical shape of the interaction zone is the key to the nonnegligible efficiency of energy transfer. (It is clear that an appreciable mechanical energy transfer is only possible if the incoming energy can avoid “being thermalized.”) The conical region is defined by the small entrance hole and the much larger exit hole in the melon. Transmission lines with tapered internal conductors are efficient transformers of electrical energy, and a tapered bullwhip can smoothly transform the energy given to a large mass, by the flick of the wrist, into roughly the same energy of a much smaller mass at the tip of the whip. The “crack” of the whip occurs when the tip of the whip goes supersonic. I believe that in a somewhat analogous manner, but of course in the opposite direction, the kinetic energy of the bullet is given in a “tapered region” to a progressively larger mass in the melon, to achieve the modestly efficient energy transfer that is demonstrated in our experiments.

A critique of the jet effect theory as an explanation for the rearward head movement of John Kennedy when allegedly shot from the right rear

The simple claim of an equal and opposite reaction to the blown out brain matter being similar to the thrust developed in a rocket or jet engine, in response to its exhaust, is deceiving if one does not understand the mechanics involved. How thrust is developed in a rocket or jet engine and the role the exhaust plays is shown and explained in the figure and paragraphs below.

Pa << Po

Pe << Po

Cutaway view of a rocket engine combustion chamber showing pressure distributions

In the above figure Pa stands for atmospheric pressure, Pe for exhaust or exit pressure, and Po for combustion chamber pressure. The high pressure Po of the combustion by-products inside the combustion chamber of the rocket or jet engine pushes in all directions to form balanced pairs of opposing forces that nullify one another, except where the hole in the system for the exhaust nozzle is placed. Here the pressure escapes at blazing speed, causing an unbalanced force at the opposite side of the combustion chamber that pushes the rocket or jet in the opposite direction to that of the exhaust. The role of the exhaust is to create a lower pressure side allowing the forward pushing opposite component of the pair to be at a higher pressure, thus causing a forward reaction, which we call thrust. The purpose of the exhaust is not to push on anything to create thrust; it is simply to relieve the pressure on one side allowing the opposite side to dominate. If it did not operate in this fashion a rocket would not work in space. Both rockets and jets are based on the same principle that causes a pressurized toy balloon to move forward and away when let go with its end untied. Thus one of the operating requirements of a rocket or jet engine is the generation of a high gas pressure in all directions in its combustion chamber, which can then be relieved at one side to gain an unbalanced force at the opposite side. With the above having been said to ensure the reader understands how a rocket or jet propels itself forward, we can now get to a sort of cross examination of what Dr. Alvarez said in his article.

Dr. Alvarez claims that President Kennedy’s head recoiled the way a rocket recoils when its jet fuel is ejected. However, he does not explain any mechanism for putting an opposite force on the head when the jet was expelled forward. He simply makes the case for the potential of the jet taking out more momentum than that brought in by the bullet. In order for a “jet effect” to have occurred a pressure would have to be built up inside the head, acting at least rearward as well as forward, which was then relieved on the forward side allowing the rearward pressure to dominate and create an unbalanced force in that direction. This usually is done with either a combustion process or having a pressure on tap in a sealed volume. The thrust in a jet or rocket engine can be computed based on the change in momentum of the exhaust gases with respect to time. However, this change in momentum is directly related to the forward acting pressure opposite that of the exhaust gases since their initial pressure values are the same but one is allowed to escape. A bullet moving through a fluid creates a high pressure conical shock wave in front of it, as shown in the figure below. The U.S. Army Wound Ballistics Research program has measured the pressure of the shock wave near the projectile as up to 100 atmospheres (1500 psi) in experiments, by shooting through tissue replicating matter. The frontal shock wave can leave some residual pressure behind it but it is orders of magnitude lower than that in front of the projectile. This residual pressure, in what is known as the temporary cavity, has also been measured by the U.S. Army Wound Ballistics Research program as 50 to 60 psi. Thus the change in momentum axiom is not valid in any “jet effect” caused by a projectile moving through an encased fluid filled object. Even if the projectile tumbles the high pressure shock wave, although less symmetric, would still be to the front as shown in the figures below.

Shock wave created by a bullet fired into a fluid.

The image was recorded using polarized light with an exposure time of 20 nanoseconds.

(A nanosecond is 1/1,000,000,000 of a second.)

Wound Profile of a lead projectile

(note the early formation of the temporary cavity)

From U.S. Army Wound Ballistics Research

Wound profile of a full metal jacketed military projectile

(note the late formation of the temporary cavity)

From U.S. Army Wound Ballistics Research

Since a “jet effect” requires a pressure opposite that of the exhaust it would be caused by the operation of this low pressure when the high pressure shock wave exits, although it would not be related to the change in momentum with respect to time of the exhausting material.

If a “jet effect” occurs when the projectile strikes and passes through the fluid filled object, it is only one of the forces acting on the object. The other force is due to shearing through the casing of the object and this force is in the direction of the projectile. The use of a taped up melon rather than an object with a shear strength and thickness close to that of a human skull is misleading. The force required for a 6.5 millimeter (.255 inch) diameter projectile to shear through the skin of a taped up melon is orders of magnitude lower than what it is for that same projectile to shear through a human cranium. The shear strength of a melon rind is approximately 70 psi. In comparison, the shear strength of a live human skull is approximately 17,000 psi perpendicular to its grain and 7,100 psi parallel to its grain. For dead bone these figures would be 8,500 psi and 3,550 psi respectively as it is approximately half the strength of live bone, although it is obviously still much stronger than melon rind. Thus the force required for the same object to penetrate and shear through the same thickness of live human skull vs. that required for a melon rind, is at least 100 times greater. Even for dead bone it is still 50 times greater,

The direction the object takes after the projectile passes through it is dependent upon the net force, or the sum of all of the forces involved. The Wound Ballistics Research program puts the temporary cavity size as about 12 times the diameter of the projectile. For the case of a 6.5 millimeter projectile, the temporary cavity would be approximately 3 inches in diameter giving a circular area of 7 inches. If the 4 atmosphere (59 psi) temporary cavity pressure acted on the entire area of this diameter it would generate a force in the direction of the shooter of 413 pounds, a significant amount. However, this force is competing with the shear forces that act in the opposite direction. The shear force for a 6.5 millimeter projectile through a .300 thick melon rind is only 17 pounds. Since the projectile passes through both sides of the melon (there is no dispute as to whether the bullet went completely through the melons) the shear force is experienced twice. If the coordinate system is chosen so that the direction of the projectile motion is positive, then for the case of the melon the net resulting force is

-413 pounds + 34 pounds = -379 pounds

showing that the net force on the melon is in the direction of the shooter. However, as the shear strength of human bone is so much greater than that of the melon rind, the shear forces on the skull are much greater. The shear force required for a 6.5 millimeter projectile to penetrate and pass through a live .300 inch thick human skull (the average thickness of a human skull is ¾ centimeters or about .300 of an inch), even using the lower parallel shear bone strength is 1,712 pounds. Since the same diameter projectile is used and the same size temporary cavity should occur, the “jet effect” will produce a similar amount of force toward the shooter of 413 pounds. The net force equation for shooting through a live human skull with a “jet effect” occurring is then

-413 pounds + 3424 pounds = + 3011 pounds

showing the net force on the skull is resoundingly in the direction of the projectile’s motion. The trick with the use of the melon to show the “jet effect”, is that the force required to shear through its skin is so low that it allows the “jet effect” generated force to dominate. This situation is not true when a human skull is involved.

The fact that it takes slightly more than 1700 pounds to shear a 6.5 millimeter diameter through a .300 inch thick item with a shear strength of at least 7,100 psi (live human skull) is indisputable. How a 10 gram (.022 pound) bullet can do this, even when moving at 2000 feet per second, needs to be explained. The force generated in the collision is a function of the change in momentum per unit time which essentially is the derivative of the momentum with respect to time or the famous equation F = ma. The equation for this is

F = (W/g) (Vinitial – Vfinal)

Impulse time

F = m dv = ma

Note: g = 32.2 ft/sec²

where if a .022 pound item is moving at 2000 ft/sec and the collision occurs with a rigid item in a time frame of 0.8 milliseconds or 1/1250th of a second, a force of 1712 pounds will be generated. A projectile traveling at 2000 ft/sec covers a .300 inch distance in 0.0125 milliseconds or 1/80,000th of a second so the time shown for the impact should not be shocking. In the case of the projectile moving into and out of a container it will have a collision with the wall of the container both on entrance and exit. Thus an even shorter impulse time is true if the strength and wall thickness of the container are known along with the penetration diameter. For the case of the head shot on President Kennedy the impulse times had to be less than 0.4 milliseconds when the projectile penetrated the skull, as the shear forces at both the entrance and exit needed to be over 1700 pounds.

In his article, Dr. Alvarez explains what occurs with both the conservation of momentum and conservation of energy in a ballistic pendulum. He goes through the equations to show how much of the kinetic energy is transformed to internal energy in the pendulum, and how little of it is conserved as mechanical energy. With the 10 gram bullet and 10 kilogram wooden block he chooses, the amount of kinetic energy transformed to internal energy by friction is over 99%. He then states that the mechanism of retrograde recoil is rather simple, if one remembers that 99.9% of the incoming energy must be accounted for. It appears that he is implying that the energy involved as friction in the ballistic pendulum should be accounted for in the matter which is blown out as a jet in the head shot, and that the jet would contain a very large amount of the energy of the bullet. His implication is misleading. In the real world, the jet would absorb only as much force and energy from the bullet as its reactive forces will allow. The amount of force and thus energy in the jet is equal to the reaction its matter exerted upon the bullet. Even so, any “jet effect” would result from the temporary cavity pressure which is independent of the shock wave except for the fact that it exits and leaves the temporary cavity pressure to dominate.

There are many who believe that the “jet effect” is a result of Newton’s third law of motion at work with the head being blown back due to the exiting material in the jet pushing against the air. Newton’s third law is at work here, as it is when any force is applied, but not the way those who believe the above think. Newton’s third law states “for every reaction there is an equal but opposite reaction”. The forces imparted by the projectile to the skull or melon when shearing through it are only as great as the skull or melon’s resistance to the shearing action, no matter how much force the projectile is capable of applying. That is one equal and opposite reaction. The equal and opposite reaction concerning the “jet effect” occurs due to the skull or melon’s inertia. The force applied by the rearward acting pressure of the temporary cavity is equal to the inertial resistance applied to it by the skull or melon. The forward moving jet is not pushing against anything in relation to the skull or melon.

It is with the use of an energy equation that Dr. Alvarez attempts to show that more momentum can be carried out by the jet than that which is brought in by the bullet. He correctly states that the momentum associated with a given amount of kinetic energy varies as the square root of the mass of the object carrying that kinetic energy. However, his use of this rule with assumed numbers for the mass of the bullet, mass of the melon, and mass of the jet has no basis nor does he provide one. He has simply provided assumed masses that work with the equation in the direction that supports his theory. To show how easy it is to manipulate the equation he uses, we can insert lower values for the kinetic energy absorbed by the jet and the mass of the jet. Then using the same equation as the one shown by Dr. Alvarez, as we shall now see, the momentum carried forward by the jet with these figures is less than the momentum brought in by the bullet. For example, if the bullet weighed 0.1% of the melon weight, and if 2.5% of its incoming kinetic energy was used to propel 2.5% of the mass of the melon forward, then the momentum of the jet expelled forward would be (.625)^1/2 times that of the incoming bullet. (again subscripts, b for bullet, j for forward moving jet, and m for melon are used.)

P_j = (2M_jK_j)^1/2 = (2 x 25M_b x 0.025K_b)^1/2

= (.625)^1/2 (2M_bK_b)^1/2 = (.625)^1/2p_b

since M_j= 0.025M_m = 25M_b, K_j= 0.025K_b. The result with these assumed values shows the jet to have less momentum than the bullet. Although these values are still probably a little high for the mass of the jet and its kinetic energy, one can now see that the simple use of this equation does not necessarily show the jet to have more momentum than the bullet. By using the words “if 10% of the incoming kinetic energy were used to propel 10% of the mass of the melon forward” Dr. Alvarez shows that he simply assumed the values he needed to make the equation work in the direction he wanted it to go. If he had proof of what he was saying he would have provided it. Since he did testing, which he says validated his theory, he could have simply weighed the melon beforehand and the remaining melon after the shooting tests, to find the actual mass of the jet displaced from the melon. He doesn’t mention anything of the sort. However, the amount of matter blown forward is inconsequential in the formation of any “jet effect”, as the “jet effect” here is strictly dependent on the magnitude of the rearward acting pressure and the area that pressure impinges upon. The temporary cavity pressure is not directly related to the shock wave momentum like the forward pressure is related to the momentum of the exhaust in a jet engine.

In reality Dr. Alvarez’s experiments on tape bound melons could have shown a “jet effect”, not with more momentum in the forward moving jet but due to the residual pressure behind the projectile in the temporary cavity, which would be the force generator. With this pressure and a cooperating permanent cavity, which simultaneously seals for the moment, a force could be generated opposite the direction of the projectile when the frontal pressure is relieved. If the permanent cavity does not seal at the entrance side, the temporary cavity pressure will be relieved and no force developed. This random lack of sealing is probably why the “jet effect” was not seen in all of the melons during the shooting tests.

The potential for a residual pressure behind the projectile does exist. For it to cause a “jet effect” it not only requires the sealing of the permanent cavity at the entrance and a shear force through the skin of the object lower than the force it generates, but it also needs to occur early enough in the projectile’s path to matter. It should be noted that Dr. Alvarez used hunting ammunition with lead projectiles rather than the jacketed ammunition of the type the 6.5 millimeter Mannlicher-Carcano would have used. As shown in the wound profiles above, the lead projectiles would have a tendency to mushroom on entrance and create an early temporary cavity. The temporary cavity with the hunting ammunition begins almost immediately after entrance. The jacketed military ammunition temporary cavity occurs much later and is due to yawing of the projectile after it has penetrated over 17 centimeters. The human head is approximately 17 centimeters in diameter and most melons are not much larger, so if shot through a skull or melon the jacketed ammunition would not begin to build a temporary cavity pressure until near exit, if at all. This could explain why Dr. Alvarez and others did not see a “jet effect” with jacketed ammunition but did with hunting ammunition. The requirement for the permanent cavity to seal would also explain why the “jet effect” on the melons was not seen every time.

The requirements for the “jet effect” to dominate and cause a motion towards the shooter are threefold and they are; the early development of a temporary cavity pressure, a low shear force through the skin or casing of the object, and an entrance side sealing of the permanent cavity. Although a “jet effect” may have occurred in Dr. Alvarez’s melon tests, the main trick was in using an object with a soft skin or casing (the melon) to reduce the shear force. The early temporary cavity produced by the lead projectile of the hunting ammunition also helped. The taping of the melon rind would allow it to resist any hoop stress due to internal pressure. Since the tensile strength of the melon rind is low, hoop stress could have caused a fracture and spoiled the test. The tape would also provide for a small entrance and better chance for permanent cavity sealing at the entrance side. The use of tape on the melons also provided these advantages without truly replicating the human skull. While the tape would tend to mock up the tensile strength of the human cranium, it would not enhance the shear strength very much. It is the shear strength that is operative here not the tensile strength. The melon tests were thus misleading and the “jet effect” seen on the melons, with the use of hunting ammunition and tape, really has no place in attempting to explain away the back and to the left head motion of President Kennedy as being possible if hit from the rear.

The shear forces generated by the bullet penetrating through the much higher shear strength of the President’s skull would preclude the appearance of a “jet effect” induced motion in the assassination. This was demonstrated at the Army's Edgewood Arsenal in 1978 during testing done for the HSCA. Ten human skulls, filled with the same tissue replicating material as that used by the Army Wound Ballistics Research program, were shot with 6.5 millimeter ammunition and all 10 skulls went forward, in the direction of the bullet. None went backward.

It seems the only plausible explanation, that matches all of the evidence, is a shot from the right front. Only a shot from the right front works scientifically. However, the place that shot has been thought to come from until the last several years, the Grassy Knoll, has been problematic with its angle. A shot from the Grassy Knoll location, when combined with the car’s location and posture of the President during the fatal shot, would have caused an exit wound on the left rear of the President’s head. All of the Parkland hospital doctors, who worked on the President for over a half hour starting just minutes after the shooting, put the massive head wound at the right rear involving both the occipital and parietal areas. That is midway up the back of the head behind the right ear. So even though many of the Dealey Plaza witnesses of the assassination rushed to the fence at the top of the Grassy Knoll, saying that is where they heard gunfire emanate from, critics of the Warren Commission’s explanation have had a hard time pointing to the Grassy Knoll. However, evidence has come up in the last several years that the fatal shot came from a storm drain on the north side of Elm Street. This storm drain is located at an approximately 12 degree angle and 70 feet to the right front of where the fatal shot hit the President. Its trajectory angle would explain the location of the right rear occipital/parietal exit wound. It would explain the spraying of the police officers to the left rear of the car (they were sprayed so hard that one of the officers, Bobby Hargis, stated afterward that he initially thought he was hit). It would explain the Harper skull fragment’s location to the left rear of the car. And finally it explains the back and to the left direction of the head movement in harmony with the other evidence. The Grassy Knoll shots could have been used for diversion so that the storm drain assassin could escape.

The Secret Service today routinely has manhole covers welded shut as part of the security for low speed presidential motorcades.

It is interesting to note, that Dr. Alvarez was involved with two Warren Commission members, Allen Dulles and John J. McCloy, in the production of the 1967 four hour long CBS pro Warren Commission documentary entitled “The Warren Report”. It was here that he says he did a good bit of work (all of it validating the Warren Commission’s conclusions), concerning the number and timing of the gun shots, and the speed at which Abraham Zapruder’s camera was running while he took his famous film of the assassination. By his own admission Dr. Alvarez did this work by watching and observing the film itself. To state that he had not noticed the President’s head movement, prior to the graduate student’s pestering him about it a couple of years later in 1968 and 1969, seems odd. It is also interesting to note, and it is public knowledge, that Life Magazine and the FBI both initially published stills from the Zapruder film in reverse order, making it appear that the head moved forward rather than rearward. Both said it was a mistake when told of the improper sequencing. It is also public knowledge today that the original and all copies of the Zapruder film were purchased from Zapruder by Life Magazine on the weekend of the assassination and locked in their vault. The film was not shown as a moving film to anyone other than a few public officials. That was until the film was subpoenaed by New Orleans District Attorney Jim Garrison for the February 1969 JFK assassination conspiracy trial in that city. Garrison needed to go to the U.S. Supreme Court to force Life to honor the subpoena and gain access to the film. It may be just coincidental that Luis Alvarez also came up with his “jet effect” theory in February of 1969, although it was not published at that time.

The public did not view the Zapruder film as a moving picture until March 1975 when a bootlegged copy, in the possession of Robert Groden who worked on the film for a Life subcontractor, was aired on Geraldo Rivera’s late night show Goodnight America on ABC. There was a public furor caused by the visible rearward head movement, in light of the Warren Commission Report’s claim that JFK was shot from the rear. The Senate Intelligence Committee chaired by Senator Frank Church and in session at the time to investigate abuses by the CIA, following the Watergate affair and its revelations, began asking serious questions about the assassination. With public outrage very high the U.S. House of Representatives moved to create a panel to review the investigations of the assassinations of John Kennedy, Martin Luther King, and Robert Kennedy. Thus the House Select Committee on Assassinations was born from this outrage. Luis Alvarez’s article, containing his attempt to show a shot from the rear was still possible even with the front to back movement of John Kennedy’s head, was published in 1976 just prior to the House Select Committee’s convening. Luis Alvarez also became involved during the House Select Committee’s hearings in trying to disprove or discredit the audio from the Dallas Police dictabelt. These tapes from a microphone on a Dallas police motorcycle in the fateful motorcade seemed to provide evidence of at least four gunshots.

The record shows that Luis Alvarez had consistently been on the scene trying to squelch any scientific proof of a conspiracy since at least 1967, when the CBS documentary was aired. This seems odd for someone who states that he was just marginally involved and forced to become involved as he implies in his story about his graduate student’s pestering of him. It is not known to me, how the connection between Dr. Luis Alvarez and certain Warren Commission members evolved, but it is certain that Dr. Alvarez’s work on explanations for the Warren Commission’s conclusions was paid for with government funding. This is stated in fine print at the end of his article. A disclaimer that the opinions expressed are not necessarily those of Lawrence Berkeley Laboratory (where he worked) or of the U.S. Energy Research and Development Administration (from whose coffers the funding was allocated to Luis Alvarez for his work) is also contained in this fine print. This tends to fly in the face of his contention that he was simply interested in the way that an average citizen, just looking for the truth, would be. Perhaps again only coincidentally, but 1967 also happened to be the year that the District Attorney of New Orleans arrested someone for conspiracy in connection with John Kennedy’s assassination.

In the 1976 article Dr. Alvarez also mentions as a colleague one Dr. John Lattimer a urologist, albeit one with gunshot experience during World War II, who was the first physician allowed to view the classified autopsy photographs and x-rays. John Lattimer has been criticized in recent years, by many in the medical community, for the flawed articles he published in the American Journal of Medicine concerning the assassination. It has also recently come to light that John Lattimer had ties to the late FBI director and another subject of controversy, J. Edgar Hoover.

There is a facet of the Warren Commission’s explanation of the assassination which provides considerable difficulty for the grouping of the fatal head shot coming from behind and the head movement explanation by Alvarez’s “jet effect” theory. The location of the sixth floor window of the Texas School Book Depository, from which it was alleged by the Warren Commission that the fatal head shot was fired, was to the right rear of the President’s head when he was shot. There is no dispute about the back and to the left direction his head took after this fatal shot. If the shot that Alvarez says caused his “jet effect” were fired from there and followed a straight trajectory, even if it were possible, a “jet effect” here would have caused his head to move back and to the right. Although there are no bones or equally dense items in the center of the human head, some might still say that the bullet could have deflected somehow inside the President’s head causing it to change direction towards the right. If this were so, there should then have been a surge to the left front caused by the force of the deflection. Neither of these type movements are seen in the Zapruder film. In fact, Dr. Alvarez intentionally stays away from talking about angles in his article, to avoid the directional problems stated above. The storm drain shot does explain the movement seen in the Zapruder film, as it would provide both the left and rearward push while keeping the exit wound at the right rear of the head.

My purpose in writing this critique was to educate those less likely to understand what the alleged “jet effect”, as proposed by Dr. Alvarez, was really saying and how it does not apply to the assassination of John Kennedy. While it may be possible in a melon and one can intuitively sense that it doesn’t apply to the assassination, it may be hard to understand and argue against without a scientific background. The fact that such a misleading explanation was put forth, in defense of the Warren Commission’s findings, should say volumes to anyone listening about that commission and its report. I did not write this critique to judge Dr. Alvarez as he is now deceased and by all accounts had many laudable achievements in a distinguished career. However, I do believe he was wrong here and that the “jet effect” should have never been proposed as an explanation for the President’s head motion. When explanations, as misleading as the “jet effect”, have been put upon us by someone working for the commission officials responsible for the official investigation, I do not believe we have been told the truth by those officials.

I believe that the search and desire for the truth in the assassination of John Kennedy is a necessary endeavor of the American people. The “jet effect” explanation has been in the way of that pursuit in some corners for years and it is time for it to be laid to rest.

The lack of belief in the official Warren Commission conclusion and the search for the truth does not need to demean our institutions simply because some of those involved in the assassination or its cover up were a part of those institutions. It simply says that a corrupted group of individuals had found their way into power or that certain individuals in power were corruptible. This type of thing is constantly guarded against in the police forces and many legal institutions in our country. Generally, it is not the case that a whole police force is corrupt if some corrupt cops are exposed. The corruption is rooted out and the system is strengthened against the same thing happening again. Unfortunately, when one reads articles espousing theories like the “jet effect” it can be seen that this was not done in the case of the assassination of John Kennedy. Apparently a sophisticated wall of subterfuge and obfuscation was erected and used by the perpetrators to prevent the exposure of the truth and their part in the affair. The “jet effect” explanation seems to have been a part of that wall.

Some might say why bother yourself over something that happened so long ago. My answer to that is that there were serious consequences for an entire generation, maybe two generations, of Americans stemming from the assassination of John Kennedy. The cynicism and lack of trust that permeated our society in its aftermath reduced our ability to function as a democracy. The wall erected to prevent the citizens of the United States from knowing the full truth concerning the assassination still stands officially. Although it has been severely damaged in the public mind (most Americans at least believe we haven’t been told the truth about the affair and that a conspiracy took the President’s life), there is still a need to maintain the pressure on it to prevent future occurrences. There is a general body of thought concerning the assassination that it was economically driven and committed by greedy fearful men, who have since had their way in the U.S. economy and its foreign policies. If that is true, it is certainly in the interest of everyone else to disprove the pieces they used to construct this wall and get to the truth. It is only through a thorough understanding by all of us, of why the assassination occurred, how it was carried out, and how it was covered up, that we the people will be able to prevent the same type of thing from happening again. Only fear of the public will prevent those who would from doing it again, if they felt it necessary for their own aims. Only public knowledge and acceptance of the truth can keep these forces at bay, denial will not defend us. Democracy demands rule by the consensus of the majority, but that requires that the majority understand how and by whom they are ruled. The future of the United States of America, and by extension the future of all of us living within its borders, can only be as strong as the truths and values upon which it is built and the collective knowledge of its people.

The people of Germany were not told the truth about Irwin Rommel’s death in 1944. They weren’t told that he was forced to take poison as a result of his part in the attempted overthrow of Hitler. The only reason we officially know what happened to him is because the Nazis did not win the war. Had they won the war there still would have been many who worked with Rommel who would have known or figured out the truth. One can only imagine that had the Nazis maintained power with their propaganda machine intact and working full time, the possible split in German society over how Irwin Rommel really died.

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