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.
