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

[John Iacoletti]

Another attempt to poison the well with a completely off-topic smear.

Elliott does that a lot.

[Michael T. Griffith]

It turns out that Dr. Art Snyder, physicist at the Stanford National Accelerator Laboratory, did not tell Josiah Thompson that there is no forward movement in Z312-313, but that the alleged forward movement of 2.3 inches does not occur. I wish Thompson had made this clear in his 2007 article. However, Thompson did end the paragraph by saying “the two-inch forward movement was just not there”:

Art Snyder of the Stanford Linear Accelerator staff persuaded me several years ago that I had measured not the movement of Kennedy's head but the smear in frame 313. The two-inch forward movement was just not there. (https://www.maryferrell.org/pages/Essay_-_Bedrock_Evidence_-_part_3.html)

I was more than happy to realize that my inference from Thompson’s statement was unfounded.

Dr. Snyder says the forward head movement in Z312-313 is about 1/3 of the Itek-Thompson value. Snyder measures the forward movement as being about 0.3 meters per second, which equals =0.63 inches in one frame. I quote Snyder:

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. (“Case Still Open: Skepticism and the Assassination of JFK,” Skeptic, volume 6, number 4, 1998, p. 53)

So instead of the head moving forward 2.3 inches in Z312-313, Snyder says it moves forward about 0.63 inches. (Take 0.3 meters per second. Take the Zapruder camera speed, which was 18.3 frames per second, or 18.3 frames per 1,000 milliseconds. Divide 0.3 meters by 18.3. That equals 0.16 meters in one frame, or 0.63 inches in one frame.)

So if a bullet from the rear could move the head 0.63 inches forward in one frame (55 milliseconds), why could not a bullet from the front have moved the head backward at the same speed?

In his “Bedrock Evidence” essay, Thompson notes that David Wimp has determined through careful measurements that the upper bodies of the limo occupants begin to move forward at about Z308. He also mentions evidence of a head shot after Z313.

The idea of a shot to the head after Z313 has surprisingly good evidence on its side. The first two reenactments in Dealey Plaza put the head shot as occurring when the limousine was 294 feet from the sixth-floor window, 29 feet farther down the street than the limo was at Z313. Dr. Mantik observes,

. . . these re-enactments as well as associated documents and eyewitness statements, place the final head shot (the second, in my view) about 30 to 40 feet farther down Elm Street than Z-313. Warren Commission data tables actually place the final shot at 294 ft. from the "sniper's" window, not the 265 ft. that corresponds to Z313. (“The Zapruder Film Controversy,” p. 24, https://themantikview.com/pdf/The_Zapruder_Film_Controversy.pdf)

Chuck Marler explores the evidence for a post-Z313 head shot in great depth in his chapter in Assassination Science, from which the following is quoted:

The distinct possibility that there was a final shot, one which struck the President after Zapruder frame 313, has been once again raised by studying the precise measurements in the 5 December 1963, survey plat, reexamining the testimony of Emmett Hudson, comparing the reference in CE-875 that the third shot struck at the "5+00" mark (which was west of Z-313), and looking at CE-2111 which stated the limousine was opposite the manhole cover at the final shot (the manhole cover is west of 313). Secret Service Agent Clint Hill also testified he heard the sound of a shot "just about as I reached it (the limousine)." (p. 258)

The 12/5/1963 survey done by the Secret Service put three marks on Elm Street to represent shots. These marks corresponded approximately to Z208, Z276, and Z358.

[Joe Elliott]

It turns out that Dr. Art Snyder, physicist at the Stanford National Accelerator Laboratory, did not tell Josiah Thompson that there is no forward movement in Z312-313, but that the alleged forward movement of 2.3 inches does not occur. I wish Thompson had made this clear in his 2007 article. However, Thompson did end the paragraph by saying “the two-inch forward movement was just not there”:

Question:

Does Dr. Art Synder provide a table, like William Hoffman did, showing his estimate of the President’s head at each frame from let’s say z305 through z320?

If all he says is that he estimates the head was only 0.63 inches ahead of the z312 position, that doesn’t give us much information on the speed of the head over time.

Dr. Snyder says the forward head movement in Z312-313 is about 1/3 of the Itek-Thompson value. Snyder measures the forward movement as being about 0.3 meters per second, which equals =0.63 inches in one frame. I quote Snyder:

So instead of the head moving forward 2.3 inches in Z312-313, Snyder says it moves forward about 0.63 inches.

I suspect the estimates are off, but at least the math checks out close, except 0.3 meters per second should be more like 0.645 inches per frame, not 0.63 inches per frame.

(Take 0.3 meters per second. Take the Zapruder camera speed, which was 18.3 frames per second, or 18.3 frames per 1,000 milliseconds. Divide 0.3 meters by 18.3. That equals 0.16 meters in one frame, or 0.63 inches in one frame.)

Should read, to make the math correct, although the estimate can still be incorrect:

(Take 0.3 meters per second. Take the Zapruder camera speed, which was 18.3 frames per second, or 18.3 frames per 1,000 milliseconds. Divide 0.3 meters by 18.3. That equals 0.016 meters in one frame, or 0.645 inches in one frame.)

So if a bullet from the rear could move the head 0.63 inches forward in one frame (55 milliseconds), why could not a bullet from the front have moved the head backward at the same speed?

A frontal bullet could start moving the head back at around 0.63 inches per frame. But the head should not continue to accelerate to 1.9 inches per frame by z318, as seen in the Zapruder film. Its basic Physics.

And no, the acceleration of the limousine cannot account for that. The acceleration is only one tenth of the acceleration needed to do this.

The idea of a shot to the head after Z313 has surprisingly good evidence on its side. The first two reenactments in Dealey Plaza put the head shot as occurring when the limousine was 294 feet from the sixth-floor window, 29 feet farther down the street than the limo was at Z313.

Dr. Mantik observes, Chuck Marler explores the evidence for a post-Z313 head shot in great depth in his chapter in Assassination Science, from which the following is quoted:

The 12/5/1963 survey done by the Secret Service put three marks on Elm Street to represent shots. These marks corresponded approximately to Z208, Z276, and Z358.

I would not say that this provide good evidence of a shot after z313 but good evidence that the Secret Service were poor surveyors.

No mark at z312-313 but marks at z208, z276 and z358 ? ! ?

[Michael T. Griffith]

Speaking of human neuromuscular reaction times, the following does not deal with Kennedy’s head movement, but it does deal with the much more  modest movement of his right hand that begins in Z225, even if the movement was involuntary. Experts for the prosecution and the defense both agreed that at least 200 milliseconds, or around four Zapruder frames, would have elapsed between bullet impact and JFK’s reaction, even if the movement was reflexive/involuntary.

Dr. Robert Piziali, a wound ballistics expert, stated under cross examination at the 1992 American Bar Association mock Oswald trial that if Kennedy began to react to a wound at Z225, this would mean the bullet could have struck him no later than Z221. Dr. Piziali, who supervised the Failure Analysis research for the 1992 mock Oswald trial, explained there would have been a delay of four frames, or about 200 milliseconds, between the bullet's impact and Kennedy's reaction to it with his right hand. He said a "reflexive reaction" to bullet impact would take "approximately 200 ms” (see trial transcript in Harrison Livingstone, Killing the Truth, New York: Carroll & Graf, 1993, pp. 224-236; see also http://www.patspeer.com/chapter12%3Athesingle-bullet%22fact%22).

Ballistics expert Dr. Roger McCarthy, testifying for the defense in the 1992 mock Oswald trial, agreed that it would have taken a minimum of 200 milliseconds, or right around four frames, for Kennedy to react, even involuntarily, as we see him start to do in Z225:

Mr. CHESLER. Now, what I'd like to do is, is move to the very next frame, 225. How much time elapsed on that day between time frame 224 was filmed and the time that frame 225 was filmed?

Dr. McCARTHY. About 56 milliseconds. This camera is running at a shade more than 18 frames/second, so between any 2 frames there's about an 18th of a second or 56 thousandth of a second. . . .

Mr. CHESLER. Now, Dr., based upon that, do you have a conclusion or an opinion as to when the President was hit with the bullet--how much before this point?

Dr. McCARTHY. Yes, as I think Dr. Piziali accurately indicated, there is a latency or a delay of about 200 milliseconds between the time that a message is delivered by either traumatic shock to the spine or by your mind to a muscle before you can get movement. . . . It takes about a fifth of a second to get all the hardware up to full power--to get the muscles to move.

Mr. CHESLER. Now, Dr., if, then, the President was hit 200 milliseconds before the movement on [frame] 225, how many frames back in the film would that be?

Dr. McCARTHY. That would be at 221 at a minimum [i.e., at the latest, and notice this is just based on timing it from a reaction at Z225]

Mr. CHESLER. And at 221 he's behind the sign, is that correct?

Dr. McCARTHY. Yes.

Mr. CHESLER. Alright. If he was hit at 221 and the Governor was hit at 224 according to the prosecution, then could they have been hit by the same bullet?

Dr. McCARTHY. No. (Killing the Truth, pp. 235-236)

This agreement by prosecution and defense experts on the time required for Kennedy to involuntarily move his right arm after bullet impact casts further doubt on the specious claim that a neuromuscular reaction could have caused JFK's backward head movement in the space of just 40-50 milliseconds. And this is not to mention the observable fact that Kennedy's reaction looks like nothing like the goat's reaction in the goat films.

[Thomas Graves]

I told you that if could not maintain civility, I would not respond to you. Go try to find someone else who will sink down to your level. I will not waste time dealing with such juvenile rudeness. Goodbye.

Dear Mike,

Well-spoken and I totally agree, but you do have a typo.

(You left out the word "you".)

--  MWT 

PS  Are you really a Trump supporter?

You do realize he's a traitor, don't you?

[Tim Nickerson]

Speaking of human neuromuscular reaction times, the following does not deal with Kennedy’s head movement, but it does deal with the much more  modest movement of his right hand that begins in Z225, even if the movement was involuntary. Experts for the prosecution and the defense both agreed that at least 200 milliseconds, or around four Zapruder frames, would have elapsed between bullet impact and JFK’s reaction, even if the movement was reflexive/involuntary.

Dr. Robert Piziali, a wound ballistics expert, stated under cross examination at the 1992 American Bar Association mock Oswald trial that if Kennedy began to react to a wound at Z225, this would mean the bullet could have struck him no later than Z221. Dr. Piziali, who supervised the Failure Analysis research for the 1992 mock Oswald trial, explained there would have been a delay of four frames, or about 200 milliseconds, between the bullet's impact and Kennedy's reaction to it with his right hand. He said a "reflexive reaction" to bullet impact would take "approximately 200 ms” (see trial transcript in Harrison Livingstone, Killing the Truth, New York: Carroll & Graf, 1993, pp. 224-236; see also http://www.patspeer.com/chapter12%3Athesingle-bullet%22fact%22).

Ballistics expert Dr. Roger McCarthy, testifying for the defense in the 1992 mock Oswald trial, agreed that it would have taken a minimum of 200 milliseconds, or right around four frames, for Kennedy to react, even involuntarily, as we see him start to do in Z225:

This agreement by prosecution and defense experts on the time required for Kennedy to involuntarily move his right arm after bullet impact casts further doubt on the specious claim that a neuromuscular reaction could have caused JFK's backward head movement in the space of just 40-50 milliseconds. And this is not to mention the observable fact that Kennedy's reaction looks like nothing like the goat's reaction in the goat films.

"Movement caused by the sudden interruption of the spinal nerves below the cord injury would have appeared much faster than a startle reflex, probably even faster than a spinal reflex. In a spinal reflex, the nerve impulse travels from the hand to the spine and back down to the muscles without having to go through the brain. This typically takes less than one-quarter of a second, or about four frames in the Zapruder film. In a direct reaction to a spinal injury, the uninterrupted impulse only has to make the 'outward' path to initiate the movement of the arm. This would probably take a little more than half the time of a spinal reflex." -- The JFK Myths: A Scientific Investigation of the Kennedy Assassination, by Larry SPersonivan, page 158

https://www.amazon.com/JFK-Myths-Scientific-Investigation-Assassination/dp/1557788472

[Dan O'meara]

Experts for the prosecution and the defense both agreed that at least 200 milliseconds, or around four Zapruder frames, would have elapsed between bullet impact and JFK’s reaction, even if the movement was reflexive/involuntary.

“The average reaction time for a visual stimulus is about 250 milliseconds. The average reaction time for an auditory stimulus is about 170 milliseconds and for a touch stimulus 150 milliseconds.” [https://www.onaverage.co.uk/other-averages/average-reaction-time]

The touch stimulus of 150 milliseconds refers to an external stimulus being applied and the reaction to it. JFK's 'hand snap' is not a reaction, it is a reflex and to imagine there is no difference between a reaction and a reflex displays a deep lack of understanding regarding this issue. The 'hand snap' is a Withdrawal (Nociceptive Flexion) Reflex in response to a stimulus applied directly to the Central Nervous System (CNS). With this type of reflex the time taken for the stimulus to be detected and reach the CNS for processing is eliminated as the stimulus is being applied directly to the CNS. This type of reflex is far quicker than a reaction.
The 200 millisecond measurement you quote is hopelessly outdated and is reflected in your analysis.

[Tim Nickerson]

“The average reaction time for a visual stimulus is about 250 milliseconds. The average reaction time for an auditory stimulus is about 170 milliseconds and for a touch stimulus 150 milliseconds.” [https://www.onaverage.co.uk/other-averages/average-reaction-time]

The touch stimulus of 150 milliseconds refers to an external stimulus being applied and the reaction to it. JFK's 'hand snap' is not a reaction, it is a reflex and to imagine there is no difference between a reaction and a reflex displays a deep lack of understanding regarding this issue. The 'hand snap' is a Withdrawal (Nociceptive Flexion) Reflex in response to a stimulus applied directly to the Central Nervous System (CNS). With this type of reflex the time taken for the stimulus to be detected and reach the CNS for processing is eliminated as the stimulus is being applied directly to the CNS. This type of reflex is far quicker than a reaction.
The 200 millisecond measurement you quote is hopelessly outdated and is reflected in your analysis.

SPersonivan's "uninterrupted impulse" theory would also cut the response time in half. However, I'm not fully onboard with that theory. It doesn't accurately account for Connally's rapid reaction. SPersonivan wrongly has Connally reacting later than Kennedy.