Dictabelt Motorcycle Was NOT Part of the Kennedy Motorcade: New Sabato Book

[Bolo Boffin]

Last edited Tue Oct 22, 2013, 01:45 AM - Edit history (1)

From page 243 of Larry Sabato's new book, "The Kennedy Half Century."

New technologically advanced audio research conducted for this book on all the Dallas police recordings of the Kennedy assassination conclusively proves that the Dallas police motorcycle with the stuck microphone was not travelling as part of the presidential motorcade at the time the shots were fired at President Kennedy. Thus, the 1979 conclusion by the House Select Committee on Assassinations is wrong. Not only does the Dictabelt not prove the Committee's assertion about a shot from the grassy knoll, we can find no evidence of gunfire (on the recording) at all, and thus it cannot be used to prove that Oswald was the lone gunman or that there was more than one shooter in Dealey Plaza. Previous scientific studies have either been fundamentally flawed because of a belief that the motorcycle was an integral part of the presidential motorcade, traveling close to President Kennedy's limousine, or because of their incorrect or nonexistent identification of the officer with the stuck motorcycle.

The officer with the stuck motorcycle was in the vicinity of the Trade Mart and nowhere near Dealey Plaza. The Dictabelt does record the motorcade as it passes the stationary motorcycle.

The officer was Willie Price, who had been assigned to monitor the corner of McKinley and Harwood. After the motorcade passed him there, he was instructed to go to the Trade Mart and did so. He had been given a substitute motorcycle that morning with documented problems with a sticking microphone.

Furthermore, three of the "gunshots" are similar to nine other impulses on the Dictabelt recording. There are "no characteristics that reliably distinguish any of the impulses from the rest." These are more likely sounds from the motorcycle itself than gunshots.

The third impulse of the four considered to be gunshots by the HSCA is the one associated with the grassy knoll. There are three other impulses on the Dictabelt to which it is "nearly identical" occurring around the same time. The only reason this impulse was considered by the HSCA appears to be that it matched their timing of the Dealey Plaza gunshots.

Filtering out the sounds of the motorcycle engine make the "gunshots" disappear almost entirely.

The Dictabelt recordings are invaluable evidence of the police actions that terrible day, but the one used by the HSCA to determine conspiracy is of no use whatsoever in determining the events of Dealey Plaza.

ETA: For people interested in the forensics on the audio analysis, the white paper has been released:

http://www.thekennedyhalfcentury.com/pdf/Kennedy-Half-Century-Audio-Research.pdf

[zappaman]

1. Doesn't matter.

CTers will still bring up the HSCA conclusion and conveniently overlook this.
And why isn't this in GD where all JFK conspiracy talk belongs?

[MrMickeysMom]

2. Don't go overboard with the crazy talk, there BB...

That sounds a little bit on the paranoid side...

Perhaps you miss the actual responses? I just read your relentless rants and crying as to where discussion belongs. I saw an actual discussion regarding a great conference which reminds the world that we are 50 years of the conspiracy reality of President Kennedy's assassination.

Totally appropriate GD conversation, in spite of your crying and ranting and general dumping into the thread. The fact is, no one can have a conversation about a conference that deals with our greatest POTUS if it reminds them of the conspiracy reality.

conspiracy reality.... which enrages you to respond with "CT"

Get over it... dicta belt or not... it's a conspiracy reality, and for some paranoid reason, that sets you off into rages, regardless where this discussion is held.

By the way, as a "host" of creative speculation, who coined that gem in DU's discussion category... Did you get to do that as one of the "hosts", BB?

[Bolo Boffin]

3. Perhaps you shouldn't use emotional language to describe my responses, MrMickeysMom.

Because you aren't very good at describing my actual state of mind when I post here. As a tool to insult and shame me, it works quite well for you. But that seems to be its only validity, and as such you are advised to keep your projections of my emotions to yourself. Since I an the only person here who can accurately portray my emotions, you should leave the mindreading to the psychics.

So what's left to respond to in this odd reply to my OP?

No, Octafish's report on a conspiracy theory conference belongs here in CS. You would be as capable of reading it here as there. It would lose none of its informative qualities being posted in the group it belongs in.

By the way, as a "host" of creative speculation, who coined that gem in DU's discussion category... Did you get to do that as one of the "hosts", BB?

I have no idea what you mean by this. I didn't write the terms of service, I didn't write the SOPs for any forum or group here, and I had no party in making any of the forums or groups here. The administrators did not consult me when they named this group Creative Speculation. They did not ask my opinion when they wrote the terms of service. I had no part in this as a host (no need for scare quotes, I actually am one of the hosts here). My being a host happened after DU 3 opened its doors with all this already in place. I am sorry if this disappoints you, but I can offer no remedy for the truth.

So now we are down to Dictabelt or not. The Dictabelt is the part of the story we are talking about in this thread. That you would continue to believe a conspiracy killed JFK anyway is something I had already suspected. Now that that's out of the way, what do you have to say about the subject at hand?

[MrMickeysMom]

4. No we are not "down" to anything except you continue to cry over things you cannot control, BB

How in the world would I know your actual state of mind when you post here? All I know is that you complain over and over again when people attend a conference about the greatest unsolved crime when the greatest POTUS is gunned down. Then, you post about dicta belts.

Thanks for the explanation that you don't write SOPs. Since you seemed to say you respond to alerts that deal with them, I thought you had something to say about "creative speculation".


It's amazing that the assassination of JFK even belongs in "creative speculation", but if you're going to cry when the subject of a conference dealing with the assassination is discussed in GD, I have to join others in wondering if the subject of JFK could be anything BUT a conspiracy that is real. So, why the hell is it supposed to be posted in CS?

The assassination of JFK is a conspiracy reality. Who told you a conspiracy killed JFK? I did not. The murder is unsolved. These two things are not equivalent.

I attended one day of a conference where forensic realities were discussed, motives of foreign policy by truly recognized authors were brought to consider, and witnessed evidence and other facts were discussed in an inter-active format. The presenter were experts in the field of forensic science and had referenced historical fact. You should be interested in understanding in this as a screen writer, if not a "liberal". Many, many others continue to study and still probe their members of congress to re-open the JFK assassination case since I it is an unsolved murder.

But, you are willing to believe a lone gun theory. Now, THAT is a conspiracy theory...

Now, why is that? It's because so many persons willing to believe what cannot be proven by forensic science (then Junior Senator Arlen Specter single bullet "theory", which most Americans DO NOT believe. Also, evidence cannot demonstrate it). You are willing to BELIEVE that theory. You and others conspire to discredit anyone who talks about a conference offering best evidence practice. What irony! If you or any of the others who conspire the ignorant Specter THEORY did one minute of considering, you'd be forced to examine evidence. However, after being exposed to the facts and conclusions of the House Select Committee who were mandated by the American people DISGUSTED with the Warren Report, you choose to swallow that Specter THEORY hook, line and sinker.

Woweeee!

[Bolo Boffin]

5. Thank you for your concern. n/t

[Spider Jerusalem]

6. You clearly don't have any idea what you're talking about

and are therefore unqualified to have an opinion.

It's because so many persons willing to believe what cannot be proven by forensic science (then Junior Senator Arlen Specter single bullet "theory", which most Americans DO NOT believe. Also, evidence cannot demonstrate it)

It can in fact be proven forensically. Kennedy and Connally react at the same time. Frame 224 of the Z-film, Connally's jacket lapel flips forward for an instant (it can only be seen in frame by frame analysis and comparison of adjacent frames). The alignment of the two men in the car was such that a single bullet would be following a line to pass through both of them. The "magic" bullet (which is in fact not magic at all) struck Kennedy in the back and exited his throat, passing through soft tissue; then struck Connally, seated inboard and below Kennedy, entering his side but being deflected along a rib and not entering the chest cavity; it exited under his nipple, and struck his wrist (by now, slowed by its passage through two bodies, travelling at a much slower velocity), fractured his radius and, spent, entered his thigh (a relatively shallow wound). Those massively deformed bullets you see pictures of in the conspiracy books? Were fired through the wrists of cadavers at point blank range, without the deceleration caused by transit of soft tissues. Ever heard of John Lattimer? He conducted a test where he fired a bullet from a similar rifle with identical ammunition, using the actual relative positions of JFK and Connally, and, know what he found? That a single 6.5mm jacketed Carcano bullet is more than capable of causing all the observed "single bullet" wounds...and that the test bullets he recovered were relatively minimally deformed (being very similar to CE399, the "pristine" bullet).

The trajectory not only works, tracing the path the bullet that caused Kennedy's back wound and throat wound (exit obscured by the tracheotomy performed at Parkland), given the relative positions of the two men, there is nowhere else it COULD have gone. (And that trajectory, traced backwards? Goes straight to the sixth-floor book depository window.)

[MrMickeysMom]

7. In fact, I do know what I'm talking about...

The single bullet theory is forensically proven to be wrong.

If persons like you choose to only read what supports your ideology, it's nobody's fault but simply your own ignorance rearing a very ugly comment.

If you wish (which you don't) references (like you didn't supply), I'll point you to them. Reading for content and understanding is really, really, really, really GOOD in your case.

Good luck with wanting to understand, but that silly unscientific rant tells me you're in need of facts. You are entitled to your own opinion, but not your own facts, Spider.

[Spider Jerusalem]

8. "Forensically proven to be wrong", by whom?

http://www.jfk-online.com/jfk100sbth.html

The trajectory not only works, given the relative positions of Kennedy and Connally, the angle of Kennedy's back wound and the angle of exit at the throat and the reconstructed trajectory, any bullet exiting Kennedy's throat on that path would have HAD to have struck Connally. There is literally nowhere else for it to go. (And the wound in Connally's back was elliptical, not circular; it was caused by a bullet that was already tumbling.)

I don't see any "unscientific" here except from you; you make assertions that are easily refuted by evidence.

[MrMickeysMom]

9. First, use actual references, Spider, not YouTubes designed for debunking buffs...

Like this one from Josepina C. Aguilar, MD, “Shored gunshot wound of exit,” (Am J Foren Med Path 1983; 4(3):199-204). :

· The bullet wound in Kennedy’s throat was not acknowledged, not described, and not documented in any way by the pathologists during the autopsy.

· Subsequent investigations could not possibly examine the documentation of the remains of the bullet wound in the throat – there was none, other than a poor photograph, taken from too far away to show any detail.

· The Clark Panel was not guided by the scientific principles described by its most prominent member, Alan R. Moritz: the Panel failed to “record a sufficiently detailed, factual, and noninterpretive description of the observed conditions [whatever details suggested the wound was ‘characteristic of an exit’ at the exclusion of an entrance], in order that a competent reader may form his own opinions in regard to the significance of the changes described.”

· Physicians who actually saw the wound gave several reasons for their interpretation of its nature: an entrance wound.

· Entrance wounds need not be perfectly smooth.

· Entrance wounds need not have abrasion collars.

· The size of entrance and exit wounds is affected by the bullet’s velocity.

· Exit wounds can be small if the area of the bullet presented to the skin is also small – and if its exiting velocity is low.

· Abrasion collars of exit wounds are much larger and, in other ways, are distinctly different from those of entrance wounds.

· The known details about the back and throat wounds of John F. Kennedy suggest both could be either entrance or exit wounds.

· The back wound could have been the exit of a bullet that entered the body through the throat. Many researchers doubt this because no hole was reported in the trunk of the limousine; they believe such a trajectory would require the bullet to also penetrate the trunk. This is not necessarily so: if the bullet had exited with very little energy – perhaps after traveling from afar – it would not have penetrated the trunk.

· The back wound could have been the entrance of a bullet (underpowered) that barely penetrated, then fell out, into oblivion. (A bullet superficially penetrated the thigh of Governor John Connally, creating a round,10mm wound, and somehow leaving a small fragment 8mm beneath the skin. This bullet had very little energy -- allegedly -- because it had already perforated Kennedy’s neck, then Connally’s chest and wrist.)

· The abrasion collar on Kennedy’s throat wound was consistent with an entrance – and most definitely not that of a shored exit.

· There is no reported evidence that Kennedy’s shirt collar contained crushed skin.

· If Kennedy’s throat wound were an exit, the bullet that created it could not have had sufficient velocity to perforate Governor John Connally’s chest and wrist.

· If Kennedy’s throat wound was an entrance, it was a typical entrance.

[Spider Jerusalem]

10. Wrong

Kennedy's throat wound was an exit wound; the bullet passed through his shirt collar, which was compressing the skin of the neck. The ballistics assertions made there are also deeply flawed (as it's been shown that a 6.5mm Carcano possesses the ballistic characteristics and velocity to cause wounds similar to those observed in Kennedy and Connally).

http://mcadams.posc.mu.edu/factoid5.htm

[MrMickeysMom]

11. McAdams... it was predictable...

"You buffs have been cooperating marvelously with my scheme to make this group [alt.conspiracy.jfk] a shambles."

John McAdams

You know, I ran into John McAdams a few days ago at the JFK conference we just had here in Pittsburgh. He clearly has his marching orders and openly admits it above.

Here's another reference for people who actually want to know each other-

http://www.blackopradio.com/pod/black625a.mp3

Provision of real details or Parkland Hospital physicians who reported on the state of Kennedy's actual entrance wounds, or those historians who studied the testimony that was not included in the Warren Report AND conclusions of the House Select Committee on Assassinations don't mean much to the willfully ignorant.

If your response to this second reference is to find another one of McAdams claims, I'll simply conclude that you are a debunker buff and I don't so much value catering to major groupies. You want to know this stuff? Then, get serious, pal.

[Spider Jerusalem]

12. Sorry, but...

the recollections of emergency-room physicians working under stress in a futile attempt to save a man's life probably aren't going to be worth quite as much as the actual autopsy report and photos. (Also, logical fallacy much? Try addressing the evidence presented and not the source.)

[MrMickeysMom]

13. I'm convinced...

... You've ventured into the, "I don't care about any facts, I'll just keep hitting the "response button" territory.

That has to be the most ridiculous response I've read to that kind of statement... "ER physicians working under stress ... probably aren't going to be worth QUITE AS MUCH AS THE ACTUAL AUTOPSY REPORT" ????

I'm a health care practitioner and critical care therapist who has worked some trauma in my many years as a respiratory therapist. I know the ER and understand that the physician who is working with his elbows half way down an airway on behalf of someone who gets his brains blown out knows what they see, what they need to do, when to do it, and what the fuck, upon calling the code, the outcome of that fucking trauma was. HOW RIDICULOUS OF YOU.

You're out... Go learn something... nice try in helping out the DICT-A-BELT thread!!! ... Jeebus Chriiisssss!!!!!!

[Spider Jerusalem]

14. Nice try:

From the report of the House Select Committee on Assassinations, Volume VII. (Emphasis added.)

(153) The various accounts of the nature of the wounds to the President differ significantly. As revealed in Section 2 of this volume, "Performance of the Autopsy," eyewitness descriptions of the wounds, as described by staff at Parkland
Memorial Hospital, differed from those in the autopsy report, as well as from what appears in the autopsy photographs and X-rays.(1) Further, the reports of FBI agents Silbert and O'Neill referred to "surgery" of the head area being evident when the body arrived for the autopsy, (2) yet no surgery of the head area was known to have been performed. Finally, the Clark panel--the panel of experts assembled in 1968 by then-Acting Attorney General Ramsey Clark--said the entrance wound in the President's head was 10 centimeters (almost 4 inches) higher than was described by the autopsy pathologists. (3)

(154) Critics of the Warren Commission's medical evidence findings have focussed on the observations recorded by the Parkland Hospital doctors. (4) They believe it is unlikely that trained medical personnel could be so consistently in error regarding the nature of the wounds, even though their recollections were not based on careful examinations of the wounds.

(155) In disagreement with the observations of the Parkland doctors are the 26 people present at the autopsy. All of those
interviewed who attended the autopsy corroborated the general location of the wounds as depicted in the photographs; none had
differing accounts. (5) Further, in 1967 the autopsy pathologists, Drs. Humes, Boswell, and Finck, as well as Dr. James H. Ebersole, the acting chief of radiology, and one of the autopsy photographers, John Thomas Stringer, viewed the autopsy photographs or X-rays, or both, and verified them as accurately portraying the wounds of President Kennedy. (6)

(156) Aside from using scientific analysis to determine authenticity and verify that no alterations had been made, the committee also considered what reasonably might have happened. It assumed that if the Parkland doctors are correct, particularly with respect to the gaping hole in the back of the President's head, then it would mean: (1) The autopsy photographs and X-rays had been doctored to conceal this hole; (2) the body itself had been altered, either before its arrival at Bethesda or during the autopsy so that the hole was not obvious in the photographs and X-rays; or (3) the photographs and X-rays were not of President Kennedy. Further, if the Parkland doctors are correct, then the autopsy personnel are incorrect and either lying or mistaken.

(157) It did not seem plausible to the committee that 26 persons would be lying or, if they were, that, they could provide such a consistent account of the wounds almost 15 years later. Second, it is less likely that the autopsy personnel would be mistaken in their general observations, given their detailed and thorough examination of the body. Consequently, it seems reasonable to assume that the autopsy personnel were correct.

(158) If the autopsy doctors are correct, then the Parkland doctors are incorrect and either lying or mistaken. It does not
seem probable that they are lying, because it would be difficult to maintain a conspiracy of lying among the approximately 14 persons involved for 15 years. On the other hand, it does seem possible, that the Parkland personnel could be mistaken, given their cursory observations of the wounds, the brief period of time they examined the President, and their function at the time: To administer emergency procedures to save the life of the President, rather than to document the nature and location of his wounds.

(159) The theoretical possibility also exists that both Parkland and the autopsy personnel are correct in their observations and that the autopsy photographs and X-rays accurately reflect the observations of the autopsy personnel. This could have occurred if someone had altered the body while in transit from Parkland Memorial Hospital to Bethesda Naval Hospital. This possibility however, is highly unlikely or even impossible. Secret Service agents maintained constant vigilance over the body from Parkland to Bethesda and stated that no one alter the body. (7) Second, if such alterations did occur, it seems likely that the people present at the autopsy would have noticed them; in which case they are now lying about their observations. As stated previously, this does not appear likely.


(160) A further complicating factor could be the possibility that all persons are somewhat mistaken in their observations or their memories of them and that the autopsy photographs and X-rays do not portray the wounds in sufficient detail to resolve the matter. This possibility would not, however, account for the major disagreement between the Parkland and autopsy personnel: A large, gaping wound in the rear of the head.

(161) Consequently, without considering any scientific analysis to evaluate authenticity and any possibility of the autopsy photographs and X-rays having been altered, appears more probable that the observations of the Parkland doctors are incorrect.

PART II. PROCEDURES EMPLOYED IN EXAMINING THE AUTOPSY PHOTOGRAPHS AND X-RAYS

(162) As mentioned, the committee did, however, subject the autopsy photographs and X-rays to scientific analysis. These
examinations by the committee's consultants established the inaccuracy of the Parkland observations. The experts concluded
that the autopsy photographs and X-rays were authentic and unaltered, confirming the observations of the autopsy personnel and providing additional support for the conclusions of the medical consultants.

(163) From the beginning, the committee's investigative approach in the medical evidence area was to assume nothing about
the authenticity of the photographs and X-rays. To conduct the analyses to determine whether the photographs and X-rays could be
identified as being of the President and whether they were altered, the committee retained experts in the following areas: Anthropology, forensic dentistry, photographic interpretation, forensic pathology, and radiology.

(164) Anthropologists studied the autopsy photographs in an attempt to verify the consistency of the subject matter
specifically, whether the photographs of the rear of the head could be identified as being consistent with photographs of other
views of the head in which the President's facial features are recognizable. The anthropologists determined that the posterior
photographic views of the head are identifiable as part of the same head as is visible in the side or front views and hence
concluded that the posterior views are photographs of President Kennedy. (8)

(165) The anthropologists also studied the autopsy X-rays in comparison with premortem X-rays of President Kennedy, obtained from the Kennedy Library in Waltham, Mass. (9) The premortem X-rays had been collected by the Library from a number of different sources (10) over a period of a couple of years.(11)

(166) By studying the premortem X-rays, the anthropologists were able to observe a number of unique anatomic characteristics
whose absence or presence among the autopsy X-rays would, in their opinion, be determinative of whether the two sets of X-rays
were of the same person. (12) Some of the anatomic characteristics they noted included turcica, cranial sutures, vascular grooves and the air cells of the mastoid bone. (13) The anthropologists were able to observe enough of these anatomical features among the autopsy X-rays to conclude that the autopsy and premortem X-rays were taken of the same individual. (14)

(167) The committee also retained an expert in dental comparison, Dr. Lowell Levine, a forensic odontologist (15) experienced in the identification of victims of unnatural death, including, for example, individuals killed in airplane crashes. Dr. Levine also compared premortem X-rays with the autopsy X-rays. He was confident in his conclusion that the three autopsy skull X-rays are identifiable as being of the same person as the premortem dental X-rays of President Kennedy. (16) Dr. Levine presented his conclusions in his public testimony before the committee on September 7, 1978.

(168) Once it was determined that the autopsy photographs and X-rays were of the President, the committee used relevant
scientific expertise to look for evidence of alteration. Different techniques were used for studying the photographs and X-rays.

(169) Members of the committee's photographic panel carefully studied the autopsy photographs, negatives and transparencies.(17) There were a number of features the panel members noticed that were relevant to the issue of authenticity, including: emulsion numbers on the films, a pentagonal shaped light spot, and a number of sets of photographic stereo pairs.(18)

(170) On April 8, 1978, David Eisendrath contacted Kodak to determine what information, if any, could be gleaned from the numbers visible on the autopsy films. (19) David Greenlaw responded for Kodak on June 8, 1978, providing information that indicated the numbers matched emulsion batches produced in 1963 and, in one film type, an operator number which was discontinued in 1969.(20)

(171) Several stereo pairs which the panel observed among the autopsy photographs were suitable for stereoscopic viewing. A stereo pair is created when the photographer takes two pictures of a particular scene with either the camera or the object in slightly different position. According to Scott, (21)
A pair of stereo pairs enables one to see the scene in three dimensions; stereo pictures add depth to the perception of the
photographed scene in much the same way as a pair of human eyes, separated from one another in space, can perceive depth.

(172) Also according to Scott, stereoscopic viewing heightens the ability of the human eye to perceive differences between the two photographs of a stereo pair:
To successfully avoid detection of picture alteration requires that each picture of a pair of pictures be altered identically, which is essentially impossible, particularly with a stereo pair * * * Any nonidentical alteration of the pictures of a pair is
readily noted when pairs are viewed stereoscopically or microscopically. (22)

(173) Fortunately, the autopsy photographer had taken two or more pictures of each scene, some of which were stereo pairs
because of slight differences. (23)

(174) Scott believed there were pairs of autopsy photographs that provided sufficient stereoscopic viewing quality to permit the conclusion of authenticity, including: The back of the head (Nos. 42 and 43), top of the head (Nos. 32 and 33, and Nos. 34 and 37), the large skull defect (Nos. 44 and 45), and the head from the front right (Nos. 26 and 28).(24)

(175) Scott said that in these he "* * * did not find any indication or evidence that any of the pictures were altered * *
*" and thus concluded that the photographs for which there were stereo pairs "* * * are authentic photograph." (25)

(176) Calvin McCamy, a photogrammetrist, testified in public session of the select committee on September 7, 1978, on behalf of the photographic evidence panel on the issue of the authenticity of autopsy photographs. He agreed with Scott's assessment of the authenticity of the stereophotographic views and added that in his analysis, he found additional stereo pairs permitting the additional conclusions that the photographs of the back wound (Nos. 38 and 39) and of the anterior neck wound (Nos.40 and 41) are authentic.(26)

(177) Dr. Gerald McDonnel examined the premortem and postmortem X-rays for evidence of alteration.(27) He reported
that an alteration of the images "* * * should be readily * * *"discernible in a number of ways:
a. Observation of a difference in density of the images,
b. Discontinuity of anatomical structures,
c. Alteration of continuity of an abnormal pattern, or
d. Production of an image which is not anatomical or an image of an impossible pathologic process.(28)

(178) Dr. McDonnel concluded that "[t]he radiologic images both ante mortem and post mortem, have not been altered in any
fashion ..." except for two small areas of thermal damage and "minor * * * discoloration of the images due to incomplete processing of the film * * *." Neither of these conditions affected the conclusion that the images were not altered "* * *to provide a false image * * *" nor "* * * to produce misinformation and therefore improper conclusions." (29)

For further explanation of the authenticity of the autopsy photographs and X-rays, see paragraphs 512-604 of the Report of the Photographic Evidence Panel.

PART III. CONCLUSIONS

(179) From the reports of the experts' analyses of the autopsy photographs and X-rays, the evidence indicates that the
autopsy photographs and X-rays were taken of President Kennedy at the time of his autopsy and that they had not been altered in any manner.

http://mcadams.posc.mu.edu/autopsy2.txt

[Bolo Boffin]

15. In addition, there's the simple fact that the Zapruder film corroborates the autopsy doctors.

There is no wound to the back of JFK's head visible in the Zapruder film. After the initial push forward so many JFK conspiracy advocates like to ignore, there's the "back and to the left" motion that has become a virtual mantra for them. But that means the back right of JFK's head is visible to the camera. There is no large gaping wound there.

So no large back-of-the-head wound in the Zapruder film and no large back-of-the-head wound at the autopsy. The obvious conclusion is that the Parkland doctors were mistaken.

McClelland himself wavered in this description when speaking to Vincent Bugliosi for his JFK assassination encyclopedia, Reclaiming History. McClelland does not think the autopsy doctors are lying or trying to mislead anyone and he even stated that he may have drawn that wound too far back in his sketch for Josiah Thompson's book. Michael Baden's explanation, reported by Bugliosi, seems the best one for the discrepancies:

Since the thick growth of hair on Kennedy's head hadn't been shaved at Parkland, there's no way for the doctors to have seen the margins of the wound in the skin of the scalp. All they saw was the blood and brain tissue adhering to the hair. And that may have mostly been in the occipital area, because he was lying on his back and gravity would push his hair, blood, and brain tissue backward, so many of them probably assumed the exit wound was in the back of the head. But clearly, from the autopsy X-rays and photographs and the observations of the autopsy surgeons, the exit wound and defect was not in the occipital area. There was no defect or wound to the rear of Kennedy's head other than the entrance wound in the upper right part of his head.

That's from pages 407-408. No one thinks McClelland is lying or trying to misrepresent what he saw. He's just wrong. It happens.