proof of a second gunman in the jfk assassination

1

The HSCA’s Acoustical Evidence:

Proof of a Second Gunman in the JFK Assassination

Michael T. Griffith 2021

@All Rights Reserved Sixth Edition

Contents

Introduction The NRC Panel The Motorcycle with the Open Microphone No “Audible” Shots on the Dictabelt Tape How Could the Grassy Knoll Shot Have Missed?

Crowd Noise and the Carillon Bell The Decker “Hold Everything” Crosstalk Larry Sabato’s Sonalysts Study The Grassy Knoll Shot and the Zapruder Film Five Gunshots on the Dictabelt Tape? A Summary of the Acoustical Evidence Bibliography

Introduction

In 1978, the House Select Committee on Assassinations (HSCA) announced that a police dictabelt recording made in Dealey Plaza during the John F. Kennedy (JFK) assassination contained four impulse patterns caused by gunfire, that one of the shots came from the famous grassy knoll, and that two gunmen were involved. This stunning development meant that the Warren Commission (WC) erred in claiming that only three shots were fired at President Kennedy and that only one gunman was involved.

When the HSCA acquired the police dictabelt recording, the committee hired the prestigious scientific firm Bolt, Beranek, and Newman (BBN) to analyze the tape. BBN had experience with doing acoustical analysis. After BBN completed their analysis, the HSCA asked two acoustical scientists from the Queens College Department of Computer Science, Dr. Mark Weiss and Mr. Ernest Aschkenasy, to review the BBN research. The HSCA selected Weiss and Aschkenasy because they were recommended by the Acoustical Society of America. Richard Trask explains how the tape initially came to the attention of the HSCA and then describes the analyses that were performed on it:

The original recordings of these transmissions, made over two separate police radio networks, were located in the possession of a Dallas official. Police transmissions had been recorded on Department Channel 1 by means of a

The HSCA’s Acoustical Evidence: Proof of a Second Gunman in the JFK Assassination

2

Dictaphone belt recorder and the day of the assassination this channel was used primarily for normal police activities. Channel 2 was used that same day as a communications link for the presidential motorcade. It was voice-activated and recorded on a Gray Audiograph Disk at headquarters. Though Channel 2 was apparently not in use during the period when the actual assassination occurred, by a fluke of a microphone transmitter on a motorcycle or other vehicle being stuck on the "On" position, approximately 5.5 minutes of the noises in and around the vehicle were recorded by the Dictaphone belt, including around the time of the shooting.

Though unclear to the unaided ear what the various noises recorded on the Dictabelt meant, several critics postulated that among the clatter were a number of possible gunshots. The Committee decided to give this problem over to acoustics experts. These respected acoustics scientists would analyze the nature and origin of the suspect sound impulses on Channel 1 to determine if sounds of shots had been recorded; and if so, how many, the time interval, and point of origin. In May 1978 the Committee contracted with Bolt, Beranek and Newman, Inc. to attempt the analysis. By means of sophisticated and, to the layman, complicated scientific analysis of the recordings, chief scientist Dr. James Barger located 6 impulse sequences which could have been caused by a loud noise such as a gunshot.

The Committee was urged to conduct an acoustical reconstruction of the assassination at the Dallas site. Realizing that Barger's initial findings, if true, pointed to a probable assassination conspiracy, the Committee sought an independent review of his analysis by Queen's College, New York, professor Mark Weiss and his research associate, Ernest Aschkenasy. Barger's analysis and methodology for the reconstruction were concurred by the two others, and on August 20, 1978, an elaborate test in Dealey Plaza was conducted. . . .

Three of the impulses matched an origin point at the Texas School Book Depository sixth floor, and one impulse, the third in the sequence, matched an origination point on the grassy knoll.

Asked by the Committee to further study Barger's work to obtain more certain results of his possible grassy knoll shot, Weiss and Aschkenasy put together an analytical extension to refine the estimate. They studied Dealey Plaza determining which structures were likely to have caused echoes received by the microphones. By identifying these echo-generating sources around the vicinity of the knoll, there were able to predict what "sound fingerprints" would have been created by a shot from the grassy knoll location when picked up by an open microphone. Each location of a microphone relative to a shooter's location would, by echoes generated off constant structures, produce a unique sound travel pattern which they referred to as a "sound fingerprint." The experts were confident that their precise calculations, taking numerous variables including air


3

temperature in 1963 and buildings structured after 1963 into consideration, gave them a certainty factor of 95 percent or better, that impulse number 3, previously identified by Barger, was in fact a shot fired from the grassy knoll. (Trask 131-132)

1. Texas School Book Depository 2. Dal-Tex Building 3. County Records Building 4. Houston Street 5. Elm Street 6. Grassy Knoll 7. Triple Underpass 8. Main Street

Dealey Plaza, Dallas, Texas

David Scheim, who holds a doctorate in mathematics from the Massachusetts Institute of Technology, discusses the dictabelt and its validity as proof of multiple gunmen:

Eleven years later, in March 1978, the House Select Committee on Assassinations located a trunkful of 1963 vintage Dallas Police records. . . . Among them was a dictabelt recording of “channel one” transmissions by police on the day of the JFK assassination. And on the dictabelt was a ten-second series of loud clicks and pops transmitted from a police motorcycle whose microphone control button had stuck in the “on” position. . . . Moreover, recorded time annotations fixed the time of the sounds at seconds after 12:30 p.m.—just when the shooting occurred. . . .

Indeed, there were important additional elements that corroborated the conclusion of Barger, Weiss and Aschkenasy. The positions they determined for the motorcycle at the time of the four shots traced out a path on Houston Street that fit the actual course and speed of the motorcade. . . . Moreover, an "N-


4

wave," characteristic of supersonic gunfire, appeared in each dictabelt impulse for which the police microphone was in an appropriate position to detect it, including the recorded sound of the third shot [identified by the Committee as coming from the grassy knoll]. The most striking find, however, was the exact location of the grassy knoll gunman. According to the acoustical calculations, this firing position was behind the picket fence, eight feet west of the corner. That was just two to seven feet from where S. M. Holland, a dozen years earlier, had placed the signs observed by himself and fellow railroad workers: the puff of smoke, muddy station wagon bumper, cigarette butts, and a cluster of footprints. (Scheim 25-26, 28, original emphasis)

Dr. G. Paul Chambers, a physicist who has worked with NASA, with the Naval Surface Warfare Center, and with the Naval Research Laboratory, explains some of the intricate correlations between the dictabelt impulse patterns and the impulse patterns from the Dealey Plaza test firing:

The HSCA commissioned the acoustics firm of Bolt, Beranek, & Newman (BBN) to perform a scientific analysis on the Dictabelt recording. This firm had previously successfully utilized acoustical analysis to determine the events that transpired during the Kent State shooting in 1970. Their acoustical analysis was later used as evidence presented to a grand jury to determine which national guardsman had fired first. BBN was also pointed by Judge John J. Sirica to serve on a panel of technical experts to analyze President Richard Nixon’s Watergate tapes.

Led by their chief scientist, Dr. James Barger, BBN converted the sounds on the tapes [the Channel 1 tape and the Channel 2 tape] to digitized waveforms. They then ran the waveforms through electronic filters to eliminate repetitive background noise like the sound of the motorcycle pistons firing. The firm then examined the processed waveforms for “sequences of impulses.” Their analysis indicated that there were six sequences of interest, spaced together within an eleven-second period recorded on channel 1, which could be consistent with the sounds of gunshots. . . .

Weiss and Aschkenasy reviewed Barger’s analysis and conclusions. They found that Barger’s analysis was valid and his conclusions supported by the evidence on the tape. They concurred with his recommendation to conduct live-fire tests in Dealey Plaza to determine the origin and direction of the gunshots, and they approved his plan for acoustical reconstruction. . . .

In Dealey Plaza, the sounds of gunshots would produce similar echoes. When recorded and captured on a specialized electronic device like an oscilloscope that converts sound patterns into pictures, these echoes appear as “acoustical waveforms” and appear as unique signatures of sound-producing events. In the case of a rifle shot in Dealey Plaza, the acoustical signatures would differ based on the origin, direction, and velocity of the shot, as well as the location of the


5

recording microphone. The echo patterns would depend on the timing of sound reflections off building or other structures and obstructions in the plaza. . . .

A recording was made of the sounds received at each microphone during each test shot, making a total of 432 recordings of impulse sequences. . . . Each recorded impulse sequence was then compared with each of the six impulse patterns on the channel 1 Dictabelt recording to see the degree to which significant points in each impulse pattern matched. . . .

The time of the arrival of the impulses, or echoes, in each sequence of impulses was the characteristic being compared, not the shape, amplitude, or any other characteristic of the impulses or sequences. . . .

When the BBN team performed their analysis of the acoustical waveforms, they found something extraordinary. When they compared the impulse sequences from the acoustical reconstruction to the sequences on the original Dictabelt recording, they found a number of significant matches. When the locations of the microphones that recorded matches in the reconstruction were plotted on a graph of time versus distance, it was found that the location of the microphones that recorded matches were clustered around a line on the graph that was consistent with the known speed of the motorcade (11 mph). . . .

Of the thirty-six microphones placed along the motorcade route, the one that recorded the sequence of impulses that matched the third impulse on the 1963 dispatch tape [the dictabelt tape] was farther along the route than the one that recorded the impulses that matched the second impulse on the dispatch tape. The locations of the microphones were consistent with the distance a motorcycle traveling at about 11 mph would cover in the elapsed time between impulses on the dispatch tape. . . . Applying a statistical formula, Barger estimated that since the microphones clustered around a line representing the speed of the motorcade, there was a 99 percent probability that the Dallas police dispatch tape did, in fact, contain impulses transmitted by a microphone in the motorcade in Dealey Plaza during the assassination. . . .

Weiss and Aschkenasy, specialists in sonar applications . . . examined Dealey Plaza carefully to determine which structures were most likely to have caused the echoes recorded by the microphone in the acoustical reconstruction that had exhibited a match to the shot from the grassy knoll. They verified and refined their identifications of echo-producing structures by examining the results of the 1978 reconstruction [the test firing in Dealey Plaza]. This approach allowed them to look for matches in the data with a 1 ms [millisecond] correlation. . . . Matches at this level of temporal precision substantially reduced the possibility that a match could occur as a result of random noise.

In Dealey Plaza, echoes from gunshot test patterns arrive in two discrete [different] clusters, differing in time by about 190 ms. Echoes originating from


6

structures along Elm Street arrive within 85 ms, while echoes from structures farther back on Houston Street arrive in the last 95 ms of a typical 370-ms-duration test pattern. In addition, a “muzzle blast” is usually prominent at the beginning of a gunshot acoustical pattern, while an N-wave (a shock wave traveling faster than the speed of sound due to the rifle bullet exceeding the sound barrier) arrives prior to the muzzle blast. The waveform identified as the grassy knoll shot is shown in figure 13. The presence of an N-wave in this waveform was consistent with the acoustical signature of a supersonic rifle bullet. (Chambers 96-102)

If the findings of the HSCA's acoustical experts are correct, then the tape contains at least four sound impulse patterns caused by gunshots, and one of those shots was fired from the grassy knoll (which was in front and to the right of the president's limousine during the shooting).

WC apologists, along with a few conspiracy theorists, have attacked the HSCA acoustical evidence. They claim, for example, that the absence of any crowd noise on Channel 1, which contains the identified gunshot impulse patterns, proves the motorcycle was not in Dealey Plaza, since crowd noises can be heard on Channel 2. They also argue that Sheriff Bill Decker’s “hold everything” transmission proves that the suspect impulse patterns on the tape were recorded at least a minute after the assassination, i.e., after the gunfire would have been heard in Dealey Plaza.

The NRC Panel

Most of the attacks on the acoustical evidence originated with a special panel of the National Research Council (NRC) of the National Academy of Sciences (NAS). The panel is generally called by one of three names: the NRC panel, the NAS panel, and the Ramsey Panel (named after its chairman, Dr. Norman Ramsey). The panel’s official name was the Committee on Ballistic Acoustics. In 1982, after spending over a year reviewing the HSCA acoustical materials, the NRC panel published a report that attacked the acoustical evidence.

But there are problems with relying on the NRC panel’s work. Not only did the NRC panel fail to examine items of evidence that supported the HSCA's findings, but they conducted their work in secret and would not make their raw materials available so other experts could try to duplicate their work. In addition, the NRC scholars utilized a faulty transcript of the dictabelt recording, and, according to W. Anthony Marsh and others, found it necessary to manipulate the times of the transmissions on the tape, in one case by almost a minute, in order to reject the HSCA's conclusions.

On the other hand, critics of the acoustical evidence claim that the NRC panel’s study is superior to the HSCA’s acoustical research, and that the NRC panel members were just as qualified as the HSCA's acoustical scientists. However, not one of the NRC panel members was an acoustical scientist.


7

The NRC panel claimed that the BBN acoustical experts selectively chose the impulses that they identified as gunfire patterns. Note that the NRC panel chose to refer to the BBN study as the BRSW study. BRSW stands for the last names of the four principal BBN scientists who did the BBN study: James Barger, Scott Robinson, Edward Schmidt, and Jared Wolf. Said the NRC panel,

The impulses selected for the BRSW study were not always the largest impulses. Frequently, large impulses were omitted and some impulses close to the noise level were retained. There are far more impulses that do not fall into the BRSW classification of "probably sounds of gunfire" than do. Since the results of the correlation coefficient calculations are highly dependent on the impulse and echo pattern selection process, it is especially critical that the scheme used to distinguish these sounds stand up to close scrutiny, with the process being spelled out in detail so others can duplicate the analysis. From the published reports, it is impossible to do so. Furthermore, weak spikes on the Dictabelt often are selected to correspond to strong patterns in the test patterns and vice versa. (Report of the Committee on Ballistic Acoustics, 1982, p. 13, original emphasis)

Dr. Scheim questions the validity of the NRC panel’s rejection of the acoustical evidence:

While the panel offered some valid criticisms of the methodology used in the House acoustical studies, it introduced complex and controversial assumptions and made several errors of its own. In a letter of February 18, 1983, Dr. Barger noted enigmatic features in a recording upon which the National Academy of Sciences panel relied and pointed out that it "did not examine the several items of evidence that corroborated our original findings." Barger stood by the acoustical determination of a grassy knoll shot as accepted by the House Select Committee on Assassinations. (Scheim 28)

Dr. Scheim continues,

For example, the critical Weiss-Aschkenasy conclusion of a 95-percent probability of a grassy knoll shot was treated only in a sketchy three-page appendix [in the NRC panel's report] that made one outright error--there was only one degree, not two, of freedom associated with the position of the shooter along the grassy knoll fence. This appendix also recalculated the probability by subtracting degrees of freedom adjusted in the Weiss-Aschkenasy analysis from matches obtained, an arbitrary approximation to a complex mathematical calculation, akin to computing the volume of a cube as three by adding its dimensions. The appendix itself included the admission that this critical calculation was "possibly overconservative" and "may be unduly conservative." (Scheim 408 n 120)


8

Placement of microphones during HSCA-BBN test firing in Dealey Plaza

The green circles are the microphones that recorded echo patterns that matched echo patterns of the gunshots on the dictabelt recording.

This map comes from Dr. Donald Thomas’s article “Debugging Bugliosi” https://www.maryferrell.org/pages/Essay_-_Debugging_Bugliosi.html

Gary Cornwell, the former deputy chief counsel for the HSCA, likewise takes issue with the NRC panel’s report. Says Cornwell,

The findings of Bolt, Beranek and Newman--like almost everything in the Kennedy case--have subsequently been questioned by the FBI, and by a panel assembled by the National Research Council (whose members are drawn from the Councils of the National Academy of Sciences. . . .). According to a "Notice" on the first page of the NRC report, the committee that studied the BBN findings "was chosen for their special competence and with regard for appropriate balance"--not because they were acoustics experts, which they were not.

I personally found it interesting not only that the NRC found that it had conclusively disproved the Select Committee's acoustical report and that there was no need for further study, but also that—remarkably, and just as with the findings of the Warren Commission--there was not a single dissent among any of the panel's members. (It may or may not also be relevant that, among the most vocal of the panel's members was a scientist who, before joining the panel and reviewing the acoustical study in detail, had taken strong positions in support of the Warren Commission's findings. . . .)

The NRC's principal rationale for rejecting the findings of Bolt, Beranek and Mark Weiss was that the Channel I tape contained "cross-talk" from Channel II that

https://www.maryferrell.org/pages/Essay_-_Debugging_Bugliosi.html


9

indicated that the portion of the Channel I tape containing the four impulse patterns identified as gunfire occurred at least 30 seconds after the actual assassination. The NRC offered possible (plausible) explanations as to various ways that such cross-talk could have gotten onto Channel I, including that the stuck microphone on Channel I was positioned near another microphone that was monitoring Channel II, and that the words being transmitted over Channel II were picked up (very faintly) by the stuck Channel I microphone, and transmitted and recorded on the Channel I Dictabelt in the police station. Subsequent re-recording is another possible explanation. The NRC in the end was not able to definitely state the cause. Nor were they able to verify that the Channel I tape they analyzed was the original DPD tape, and thus could not say for sure that the cross-talk had been recorded on November 22, 1963. Finally, subsequent private analysis as well as further review by Dr. Barger has revealed that the NRC's tests appear to have been conducted with the tapes being run at an improper speed, thus invalidating their calculations of when the impulse patterns at issue actually did occur in relation to the assassination.

And the NRC essentially ignored, and never did explain how, if these impulse patterns were not gunfire, their timing, sequencing, and qualitative characteristics were so extensively corroborated by the other physical and scientific evidence in the case. Was all of the meshing of such evidence simply a coincidence? . . . Several witnesses testified that one shot came from the grassy knoll, just as the acoustics indicated. Just a coincidence? The shock waves and windshield distortions were present on the shots where they should have been, and absent on the others. One more coincidence? Since the NRC described their findings as conclusive and not subject to question, one must wonder why the NRC ignored all of this evidence that corroborated the Barger and Weiss findings, but is totally inconsistent with the NRC findings that these impulses are not the actual sounds of gunfire. One might also wonder why the NRC never addressed, never discussed, and never attempted to explain other "cross talk" on the Channel I tape that is totally inconsistent with the NRC conclusion that impulse patterns evidencing four shots occurred . . . after the actual assassination. (Cornwell 112-114)

A hearing of the House Select Committee on Assassinations (HSCA)


10

The windshield distortions mentioned by Cornwell deserve further discussion, because they provide further evidence that the dictabelt recording contains gunshot impulses of JFK assassination gunfire. When the motorcycle was in a position where its windshield was between the rifle and the microphone, the impulse patterns of the shots that were fired during this timeframe contain windshield distortion; however, there is no such distortion in the impulse pattern of the one shot that was fired when the windshield was not between the rifle and the microphone. This is an astonishing coincidence if the dictabelt tape was not recorded in Dealey Plaza during the assassination. The HSCA report contains a section on this important evidence:

Weiss and Aschkenasy also considered the distortion that a windshield might cause to the sound impulses received by a motorcycle microphone. They reasoned that the noise from the initial muzzle blast of a shot would be somewhat muted on the tape if it traveled through the windshield to the microphone. Test firings conducted under the auspices of the New York City Police Department confirmed this hypothesis. Further, an examination of the dispatch tape reflected similar distortions on shots one, two, and three, when the indicated positions of the motorcycle would have placed the windshield between the shooter and the microphone. On shot four, Weiss and Aschkenasy found no such distortion.(55) The analysts' ability to predict the effect of the windshield on the impulses found on the dispatch tape, and having their predictions confirmed by the tape, indicated further that the microphone was mounted on a motorcycle in Dealey Plaza and that it had transmitted the sounds of the shots fired during the assassination. (HSCA report, pp. 74-75)

The NRC panel’s report does even mention the windshield-distortion correlations. What are the odds that random noise would generate impulse patterns that duplicated impulse patterns of gunshot sounds that had passed through a windshield? What are the odds that three out of four random bursts of noise would produce impulse patterns that mimicked windshield distortions, and that those copycat windshield distortions would occur in the correct order and interval when compared with the windshield distortions in three impulse patterns of shots fired in Dealey Plaza?

Dr. Chambers spends several pages reviewing the NRC panel’s report on the acoustical evidence and finds the report to be unconvincing, evasive, and contradictory. Here are a few of his comments on the report:

The National Research Council admitted that is calculations of the relevant probabilities may have been “unduly conservative.” In fact, the report uses the word “conservative” with regard to the statistical analysis a number of times. It then goes on to state: “Except for the rather conservative analysis above, the data do tend to cast doubt on the hypothesis of random impulse locations.” In other words, the sounds on the tape do not appear to be caused by standard random noises, like cars backfiring in Dealey Plaza. This seems to me a lot like an admission that the Bolt, Beranek, & Newman impulse sequences were indeed nonrandom data, and therefore attributable to something significant. As gunshots


11

were the only reasonable source that matched the acoustic signatures, it would appear that the NRC doubted its own conclusions.

With regard to the crosstalk synchronization, the NRC report states, in an appendix discussing this analysis, that:

“The analyses in Appendices B-1 and B-2 [of the crosstalk] may be subject to some criticism. A certain amount of subjectivity derives from the fact that the first observer was looking at the sound spectrograms from both channels while he marked points on Channel 1. . . . However, this experiment was supplemented by several variations that derived similar results. Some of these were more careful to avoid the subjectivity and to reduce considerably the dependence aspects of the experiment presented here. These are not reported in detail, because they were carried out using xerographic copies of photographs using several scales, and relatively crude measuring instruments (graph paper in place of rulers).”

This is an admission that the first technique used to confirm the crosstalk between the channels and to determine that the impulses of interest were not concurrent with the assassination was highly subjective and therefore subject to doubt. Moreover, the method they used to confirm the first technique was so low-tech that they didn’t even want to describe it. I could speculate that they employed the zoom function on the photocopier; however, precisely how they did this analysis was deliberately left vague and so there is no hope of reproducing their work. In science, if other scientists are to take conclusions seriously, it is essential to describe the methodology of what was done to reach them in detail. Otherwise, the work doesn’t have validity, because no one will be able to reproduce the results.

Dr. Barger himself responded to the issue of the crosstalk synchronization in a letter in G. Robert Blakey in 1983, after the release of the NRC report, concluding that the NRC synchronization was doubtful and that the original BBN conclusions remained valid. (Chambers 106-107, original emphasis)

The NRC panel claimed that the HSCA experts rejected other sets of impulses on the dictabelt merely because they did not have a reasonable trajectory:

Of the six sets of impulses that give high binary correlation coefficients with test shots, BRSW selected four as likely assassination shots by eliminating those whose echoes were inconsistent with a reasonable trajectory. (Report of the Committee on Ballistic Acoustics, p. 10)

Dr. Donald Thomas, a research scientist with the U.S. Department of Agriculture and one of the leading researchers on the acoustical evidence, explains why the NRC’s statement is invalid:


12

Everything in this statement is wrong. First of all, five, not six sets of impulses gave high binary correlation coefficients. Secondly, no suspect sets of impulses were eliminated because they were inconsistent with a reasonable trajectory. Five suspect patterns were identified in the lab screening and all five passed the field test (Binary correlation). Importantly, and contrary to the NRC report, all five fall in alignment with a reasonable trajectory. None were eliminated because they had an unreasonable trajectory – never happened.

The author of the introductory section of the NRC report, apparently Luis Alvarez (although all co-authors bear responsibility), deliberately misrepresented the acoustics study to make it appear that the results were equivocal and that the analysts had cherry-picked the data to reach an arbitrary conclusion.

The NRC panel spent two years trying to find a flaw in the acoustical analysis. Unable to find a serious flaw, they resorted to distortion and misrepresentation. Luis Alvarez was asked to chair the NRC panel because he was a long-time defender of the Warren Commission. Alvarez had every right to defend his positions on this issue. But he had no business serving on a tax-payer funded panel whose responsibility was to provide an unbiased review of the acoustical evidence. (Thomas, “Overview and History,” part 3)

The BBN scientists were tremendously impressed with the locational correlations between the dictabelt gunshots and the test-firing gunshots. They determined that the probability that chance caused these correlations was “less than 1%.” Figure 22 in the BBN report shows the microphone positions along the motorcycle route where high correlations were obtained. The BBN scientists referred to this figure in explaining why there was less than a 1 percent probability that chance caused the time-distance correlations:

Even a brief glance at Fig. 22 shows that the microphone locations that correspond to correlations at the three times after the first impulse tend to progress uniformly forward along the motorcade route. This conclusion can be quantified statistically by the chi-square test. If the motorcycle were not moving through Dealey Plaza at the time of the assassination, the distance along the motorcade route would be a meaningless coordinate, and the microphone locations for the correlations that exceed the detection threshold would occur at random. When the chart in Fig. 22 is partitioned into a 2 x 2 table by separating time at 5 sec and distance at 250 ft, we find 1, 6, 8, and 0 correlations in the four sections reading from left to right, top to bottom. But the expected number of correlations to be found in these four sections, if the correlations occurred at random, are 4.2, 2.8, 4.8, 3.2. The value of chi-square for the observed and expected values is equal to 11.4. There is only 1 degree of freedom in this 2 x 2 table, and the probability that this large value of chi-square could occur at random is less than 1%. Therefore, there is little doubt that the distance coordinate is meaningful, and we conclude that the motorcycle was moving


13

through Dealey Plaza and did, in fact, detect the sounds of gunfire. (BBN report, 8 HSCA 104)

And what did the NRC panel have to say about this powerful evidence? They argued that the BBN scientists had erred, that the BBN value of P<0.01 (i.e., less than 1 percent) was actually P=0.07 (i.e., 7 percent), and that therefore the “significance of the layout” indicated by Figure 22 was “considerably reduced” (NRC report, p. 37). In other words, the panel said that the probability that chance caused the locational correlations was 7 percent instead of less than 1 percent. This, of course, means that the probability that chance did not cause the correlations is 93 percent.

The NRC panel made no effort to explain the significance of the fact that their own calculation found a 93 percent probability that the locational correlations occurred because the impulse patterns on the police tape were recorded by a motorcycle in Dealey Plaza during the assassination. In fact, they did not even specifically mention this. They simply noted that they determined the probability of chance was 7 percent and acted as though they had dealt a strong blow to the BBN report. Granted, 7 percent is more than "less than 1%," but it is still an extremely low probability of chance.

The Motorcycle with the Open Microphone

The HSCA identified the microphone of police officer H. B. McClain as the mike that recorded the sounds on the tape, and McClain admitted in his testimony that his mike tended to get stuck in the “on” position. However, McClain later insisted that his motorcycle was in the wrong location to have recorded the sounds on the tape, and that he followed JFK’s limousine to the hospital immediately after the shots were fired. The HSCA’s final report took issue with McClain’s belated claim and explained why the acoustical experts identified McClain’s motorcycle as the bike with the open mike:

In his interview on September 26, 1977, McLain said that he had been riding to the left rear of Vice President Johnson's car and that just as he was completing his turn from Main onto Houston Street, he heard what he believed to have been two shots.(67) Sergeant Jimmy Wayne Courson was also interviewed on September 26, 1977. He stated that his assignment in the motorcade was in front of the press bus, approximately six or seven cars to the rear of the presidential limousine, and that as he turned onto Houston Street, he heard three shots about a second apart.(68) Neither officer was asked specifically whether his radio was on channel one or two, or whether his microphone switch might have been stuck in the transmit position.

The committee obtained Dallas Police Department assignment records confirming that McLain and Courson had both been assigned to the left side of the motorcade, (69) and it discovered photographic evidence(70) that Courson was riding to the rear of McLain, and as Courson recalled,(71) he was in the vicinity of the press bus. The available films revealed that throughout the motorcade the spacing of the motorcycles varied, but that McLain was generally


14

several car lengths ahead of Courson and therefore much closer to the presidential and Vice Presidential limousines.(72) No photographs of the precise locations of the two officers at the moment of the assassination were, at that time, found. Photographs taken shortly before the assassination, however, did indicate that McLain was on Houston Street heading toward Elm as the presidential limousine was turning onto Elm in front of the Texas School Book Depository.(73) At the time of the assassination, therefore, he would have been in the approximate position of the transmitting microphone, as indicated by the acoustical analysis. . . .

The acoustical analysis pinpointing the location of the microphone, the confirmation of the location of the motorcycle by photographs, his [McClain’s] own testimony as to his location, and his slowing his motorcycle as it rounded the corner of Houston and Elm (as had been previously indicated by the acoustical analysis),(92) and the likelihood that McLain did not leave the plaza immediately, but lagged behind momentarily after the assassination, led the committee to conclude it was Officer McLain whose radio microphone switch was stuck open.

Further, the committee noted, it would have been highly improbable for a motorcycle on Stemmons Freeway to have received the echo patterns for the four impulses that appear on the dispatch tape. As noted in more detail below, to contend that the microphone was elsewhere carries with it the burden of explaining all that appears on the tape. . . . As Aschkenasy testified, the echo patterns on the tape would only have been received by a microphone located in a physical environment with the same acoustical characteristics as Dealey Plaza.(93) It is extremely unlikely that the echo patterns on the tape, if received from elsewhere, would so closely parallel the echo patterns characteristic of Dealey Plaza. (HSCA report, pp. 76, 79)

It should be emphasized that the available photographic evidence of the assassination does not show where McClain was during the 8-9 seconds when the shots were fired. But, the photographic evidence does show that McClain was in positions before and after the shooting that would have enabled him to be in the correct locations to record the gunfire. Furthermore, no other motorcycle was in a position that would have reasonably enabled it to reach the required acoustical locations (Thomas, “Overview and History,” part 3; see also Thomas, “Debugging Bugliosi”).


15

JFK’s limousine in Dealey Plaza just a few seconds after the shooting began

JFK has already started to react to being wounded.

After McClain testified before the HSCA, he claimed he turned on his siren when he started to drive to the hospital. "Yet," notes WC apologist Gerald Posner, "on the dictabelt recording there are no sirens except nearly two minutes after the supposed shooting" (Posner 240). The HSCA’s final report addresses this issue:

Officer McLain's acknowledged actions subsequent to the assassination might explain the sound of sirens on the tape. McLain was in fact probably on Stemmons Freeway at the time Henslee noted that an unknown motorcycle appeared to have its microphone switch stuck open. McLain himself testified that following the assassination, he sped up to catch the front cars of the motorcade that had entered Stemmons Freeway en route to Parkland Hospital.(90) In any event, it is certain he left the plaza shortly after the assassination. The cars in the motorcade had their sirens on, and this could account for the sound of the sirens increasing as McLain drew closer to them, whether he left Dealey Plaza immediately or shortly after the assassination. . . .

Subsequent to his hearing testimony, McLain stated that he believed he turned on his siren as soon as he heard Curry's order to proceed to Parkland Hospital. He said that everyone near him had their sirens on immediately.(91) Should his memory be reliable, the broadcast of the shots during the assassination would not have been over his radio, because the sound of sirens on the tape does not come until approximately 2 minutes later. The committee believed that McLain was in error on the point of his use of his siren. Since those riding in the motorcade near Chief Curry had their sirens on, there may have been no particular need for McLain to turn his on too. (HSCA report, pp. 78-79)

Photographic evidence indicates that McClain did not leave the plaza immediately. Furthermore, if McClain had turned on his siren right after Curry’s order, the dictabelt would have recorded it. The fact that McClain’s siren is not heard on the police tape immediately or shortly after Curry’s order proves that McClain’s belated claim is false.


16

Another claim that McClain made after he gave his HSCA testimony was that while he was still moving on Houston Street, he saw Mrs. Kennedy climb onto the trunk of the limousine. If true, this would put him in locations different from those indicated by the dictabelt recording at key times. However, McClain’s claim is unlikely. We know that Mrs. Kennedy climbed onto the limo’s trunk no more than 5 seconds after the final shot. Intervening crowds of people and structures would have been made it difficult for McClain to have seen Mrs. Kennedy on the trunk from Houston Street. But, if McClain was where the acoustical evidence places him at this time—on Elm Street—then he would have had a clear view of Mrs. Kennedy’s actions. Moreover, Patrolman Jimmy Courson, who was at least 40 feet behind McClain, said he saw Mrs. Kennedy on the trunk just as he was turning onto Elm Street. It appears that McClain changed his story in ways that would disqualify his motorcycle as the one whose mike recorded the sounds on the dictabelt tape.

Critics do not seem to understand that the sirens could have been picked up at another location, such as the Trade Mart, by another motorcycle’s microphone and then recorded on Channel 1 along with the sounds from the motorcycle that had recorded the gunfire in Dealey Plaza. So it is not even necessary to assume that any bike in Dealey Plaza recorded the sirens.

It is curious that the same WC apologists who have repeatedly said that eyewitness accounts are generally unreliable have been quick to accept McClain’s belated account that puts him in the wrong locations for his microphone to have recorded the police tape.

If the motorcycle with the open mike was not with the motorcade during the assassination, how were N-waves of supersonic gunfire recorded on the dictabelt tape? How did they get there? How were the N-waves recorded in the correct order and interval in relation to the muzzle blasts and muzzle-blast echoes that they accompanied?

Also, how is it that the average speed of the mike during the shooting sequence on the dictabelt tape is nearly identical to the average speed of JFK’s limousine on Elm Street during the shooting? This is an astonishing coincidence if the police tape contains no sounds recorded in Dealey Plaza during the assassination.

Professor Ernest Aschkenasy put it this way when asked about the issue of the motorcycle’s location:

Mr. DODD. Let me try to conclude this, by asking you this, though. Having said that, and using the expertise that you have in acoustics, you, I think, said, Dr. Aschkenasy, that to have found a sound that you developed in your predicted response in some place other than Dealey Plaza, it would have been necessary to reconstruct, in effect, Dealey Plaza in some other place?

Mr. ASCHKENASY. Correct.


17

Mr. DODD. So that even if that sound that we hear is the third or fourth response, that would have only been able to have come, based on your expertise and your tests, only could have come from Dealey Plaza, unless you could have recreated Dealey Plaza?

Mr. ASCHKENASY. Congressman Sawyer at that time asked the question, if somebody were to tell me that the motorcycle was not at Dealey Plaza--and he was in fact somewhere else and he was transmitting from another location--my response to him at that time was that I would ask to be told where that location is, and once told where it is, I would go there, and one thing I would expect to find is a replica of Dealey Plaza at that location. That is the only way it can come out. (5 HSCA 592)

When Congressman Edgar asked Dr. Weiss if the third and fourth dictabelt shots were really an acoustical mirage from one muzzle blast, Dr. Weiss said this was impossible because every echo predicted from the dictabelt’s third shot—the grassy knoll shot—corresponded to an echo from the grassy knoll recorded during the test firing. He explained that for the third and fourth shots to be an acoustical mirage of one shot, the sound of the muzzle blast would have had to be somehow transported “to the location of the grassy knoll area, and there emitted as if it had originated from that point,” because every echo has “its own peculiar distortion, transmission characteristics”:

Mr. EDGAR . It is my understanding that due to the short time interval between shot No. 3 and shot No. 4, approximately 0.5 to 0.7 seconds, the possibility of an acoustical mirage should be considered as a possible explanation. Perhaps the most common illustration of the effect of an acoustical mirage is the optical mirage we see riding along a highway, and we look on the distance and see wet pavement, and when we get to the spot, we find it is not wet pavement, but a trick on our eyes. The phenomenon of an acoustical mirage, which I believe is called refraction or bending, is it possible that the closeness of the two shots, No. 3 and No. 4, could have, in fact, come from the same muzzle blast and could, in fact, be an acoustical mirage, a reflection, a bending off of the sound patterns, or a different approach of the sound to the microphone?

Mr. WEISS. No, sir; because in order for that to be true, you would have to, in effect, have had the sound of the muzzle blast transported by some means to the location of the grassy knoll area, and there emitted as if it had originated from that point. Since every echo that was predicted corresponded to an echo arising from a sound rising from that location, what you would have required is that echoes otherwise generated from a shot fired, say, from the depository window, would each have had its own peculiar distortion, transmission characteristics such that by some marvelous process it occurred at the microphone, intact, and at the correct position. (5 HSCA 608)


18

No “Audible” Shots on the Dictabelt Tape

Harrison Livingstone raises the issue of why no shots are audible on the tape and cites this a reason for believing the motorcycle was not in Dealey Plaza during the assassination:

Why, now, are there no shots audible on the tape? Rifle shots in such an enclosed urban space, echoing off buildings, would be very loud and certainly were heard by everyone in Dealey Plaza. Was there some technical reason that they might not record through an open mike located somewhere in Dealey Plaza? The answer is that there was no microphone open anywhere near Dealey Plaza, and so the gunshots could not have been recorded. (Livingstone 357)

The HSCA acoustical experts explained why the shots are not audible to the naked ear when the dictabelt recording is played. This has to do with the circuitry of the Dallas police department’s radio dispatch system. From the Weiss and Aschkenasy report:

The DPD radio dispatching system contained a circuit that would have greatly affected the relative strengths of the recorded echoes of a muzzle blast. This circuit, the automatic gain control (AGC), limited the range of variations in the levels of signals by reducing the levels of received signals when they were too strong and increasing their levels when they were too weak. (8 HSCA 30)

Dr. Barger discussed this issue during his HSCA testimony:

Now it was perfectly clear that these sounds were not clearly audible. There is in the field of detection theory a favorite approach called matched filtering. The matched filter is a device that is used to detect events that you have some understanding of, even though they are subaudible [not audible to the unaided ear]. Matched filters are used in radar sets commonly to detect the presence of impulsive signals in noise, even though they are not visible or audible in the raw data. There was reason to believe that applying these techniques we might be able to detect the impulsive sounds of gunfire.

The most serious problem was the motorcycle noise. There is a way to help reduce that. It is a technique called adaptive filtering. . . .

We thought once the adaptive filtering was conducted, the tape might then be noise-free enough to attempt a detection of the sounds of gunfire. . . .

Now, as I said, we realized from the outset that we were seeking to detect sub-audible events, or at least not audibly recognizable events, and this is helped by looking at the electrical waveform that represents the sounds in a form called a waveform chart. So the first thing we did was to digitize the sounds in this 5 1/2-minute tape recording to form a computer file of the information contained by that


19

digitalization, and then plot out a chart showing the waveform on the tape. (2 HSCA 18, 27)

From the HSCA’s final report:

To the human ear, the tapes and Dictabelts contain no discernible sounds of gunfire. The dispatcher's voice notations of the time of day indicate that channel 2 apparently was not in use during the period when the shots were fired. Channel 1 transmissions, however, were inadvertently being recorded from a motorcycle or other police vehicle whose radio transmission switch was stuck in the "on" position.(10) BBN was asked to examine the channel 1 Dictabelts and the tape that was made of them to see if it could determine: (1) if they were, in fact, recorded transmissions from a motorcycle with a microphone stuck in the "on" position in Dealey Plaza; (2) if the sounds of shots had been, in fact, recorded; (3) the number of shots; (4) the time interval between the shots; (5) the location of the weapon or weapons used to fire the shots; and (6) the type of weapon or weapons used.

BBN converted the sounds on the tape into digitized waveforms and produced a visual representation of the waveforms.(11) By employing sophisticated electronic filters, BBN filtered out "repetitive noise," such as repeated firings of the pistons of the motorcycle engine.(12) It then examined the tape for "sequences of impulses" that might be significant.(A "sequence of impulses" might be caused by a loud noise--such as gunfire--followed by the echoes from that loud noise.) Six sequences of impulses that could have been caused by a noise such as gunfire were initially identified as having been transmitted over channel 1.(13) Thus, they warranted further analysis. These six sequences of impulses, or impulse patterns, were subjected to preliminary screening tests to determine if any could be conclusively determined not to have been caused by gunfire during the assassination. . . .

All six impulse patterns passed the preliminary screening tests.(15)

BBN next recommended that the committee conduct an acoustical reconstruction of the assassination in Dealey Plaza to determine if any of the six impulse patterns on the dispatch tape were caused by shots and, if so, if the shots were fired from the Texas School Book Depository or the grassy knoll.(16) The reconstruction would entail firing from two locations in Dealey Plaza--the depository and the knoll--at particular target locations and recording the sounds through numerous microphones. The purpose was to determine if the sequences of impluses recorded during the reconstruction would match any of those on the dispatch tape. If so, it would be possible to determine if the impulse patterns on the dispatch tape were caused by shots fired during the assassination from shooter locations in the depository and on the knoll.(17). . . .


20

The sequence of impulses from a gunshot is caused by the noise of the shot, followed by several echoes. Each combination of shooter location, target location and microphone location produces a sequence of uniquely spaced impulses. At a given microphone location, there would be a unique sequence of impulses depending on the location of the noise source (gunfire) and the target, and the urban environment of the surrounding area (echo-producing structures in and surrounding Dealey Plaza). The time of arrival of the echoes would be the significant aspect of the sequence of impulses that would be used to compare the 1963 dispatch tape with the sounds recorded during the 1978 reconstruction.(18) The echo patterns in a complex environment such as Dealey Plaza are unique, so by conducting the reconstruction, the committee could obtain unique "acoustical fingerprints" of various combinations of shooter, target and microphone locations. The fingerprint's identifying characteristic would be the unique time-spacing between the echoes. If any of the acoustical fingerprints produced in the 1978 reconstruction matched those on the 1963 Dallas police dispatch tape, it would be a strong indication that the sounds on the 1963 Dallas police dispatch tape were caused by gunfire recorded by a police microphone in Dealey Plaza. . . .

The locations of the microphones that recorded the matches in the 1978 reconstruction were plotted on a graph that depicted time and distance. It was observed that the location of the microphones at which matches were recorded tended to cluster around a line on the graph that was, in fact, consistent with the approximate speed of the motorcade (11 mph), as estimated from the Zapruder film.(36) For example, of the 36 microphones placed along the motorcade route, the one that recorded the sequence of impulses that matched the third impulse on the 1963 dispatch tape was farther along the route than the one that recorded the impulses that matched the second impulse on the dispatch tape.

The location of the microphones was such, it was further observed, that a motorcycle traveling at approximately 11 miles per hour would cover the distance between two microphones in the elapsed time between impulses on the dispatch tape. This relationship between the location of the microphones and the time between impulses was consistent for the four impulses on the dispatch tape, a very strong indication, the committee found, that the impulses on the 1963 dispatch tape were picked up by a transmitter on a motorcycle or other vehicle as it proceeded along the motorcade route. Applying a statistical formula, Barger estimated that since the microphones clustered around a line representing the speed of the motorcade, there was a 99 percent probability that the Dallas police dispatch tape did, in fact, contain impulses transmitted by a microphone in the motorcade in Dealey Plaza during the assassination.(37) (HSCA report, pp. 68-70, 72)


21

How Could the Grassy Knoll Shot Have Missed?

The HSCA claimed that the shot from the grassy knoll missed. WC apologist Jim Moore wonders how a gunman firing from the grassy knoll could have missed:

Not once in its final report did the HSCA address how a gunman firing from the knoll might have missed, nor did it speculate on where the bullet hit. (Moore 142-143)

But subsequent research strongly indicates that the grassy knoll shot did not miss but was the shot that hit JFK’s head in frames 313-321 of the Zapruder film. The HSCA’s claim that the grassy knoll shot missed was not necessarily shared by the committee’s acoustical scientists; rather, this claim seems to have been driven by Robert Blakey, the committee’s chief counsel. Two people who worked with Blakey on the acoustical evidence have said he insisted that the grassy knoll shot be labeled as a miss. (Blakey also insisted that the gunshot at 140.3 on the dictabelt tape be rejected as a false alarm, because this shot from the rear could not have been fired by the same person who fired the three other shots from the rear.)

In any case, WC apologists are in no position to be rejecting the grassy knoll shot because of the doubtful claim that it missed. Their shooting scenario requires one to believe that the alleged lone gunman, firing from the sixth-floor corner window of the Book Depository, somehow missed not only Kennedy but the entire huge limousine from 60 feet up and from less than 160 feet away. This would have been a far more unbelievable miss than the alleged miss from the grassy knoll.

The grassy knoll seconds after JFK’s limousine left Dealey Plaza

Crowd Noise and the Carillon Bell

Some critics argue that the absence of crowd noise on the dictabelt recording proves the recording was not made in Dealey Plaza. This criticism is easily answered. For one thing, the crowd probably had stopped cheering where McClain was riding, since he was about 145 feet behind the president’s car. Even if the crowd was cheering when McClain drove by, this noise would not be audible on the tape because of the noise from the bike’s engine.


22

For years some critics regarded the sound of a carillon bell on the dictabelt tape as evidence that the tape was not recorded in Dealey Plaza. About 8 seconds after the last shot on the tape, the sound of a carillon bell can be heard. Critics argued that there was no carillon bell in or near Dealey Plaza, and that therefore the bell sound on the tape proved the open mike was not in Dealey Plaza 8 seconds after the shooting.

The HSCA acoustical scientists were aware of this issue, and they plausibly argued that other police microphones could have recorded the bell sound, noting that a number of other policemen talked on Channel 1 (5 HSCA 591-592). After the HSCA investigation, researchers discovered that in 1963 there was carillon bell near Dealey Plaza, and they found a KXAS TV-News video tape made in Dealey Plaza in 1964 on which the sounds of the nearby carillon bell can heard.

In 1982, an analysis of the dictabelt tape by some IBM scientists concluded that the bell sound is on both channels. The IBM scientists speculated that the bell sound might not be a bell sound but radio interference whose frequency mimicked a bell sound (Thomas 2013:643-644).

The Decker “Hold Everything” Crosstalk

Almost immediately after the final gunshot on Channel 1 of the police tape, Sheriff Decker's “hold everything” crosstalk occurs. However, this crosstalk originated on Channel 2 and was recorded about 60 seconds after the assassination on that channel. All the gunshot impulse patterns occur on Channel 1. Using Decker’s crosstalk as their time indicator, critics argue that the crosstalk proves that the gunshots were recorded about 60 seconds after the assassination, and that therefore they cannot be gunshots but must be random noise. But this argument is contradicted by considerable evidence. For starters, Deputy Chief Fisher’s “I’ll check” crosstalk, which occurs simultaneously on both channels, occurs 2 seconds before the first dictabelt gunshot on Channel 1, and about 8 seconds before the 12:30 time notation on Channel 2. The Fisher crosstalk alone proves that the dictabelt gunshots were recorded during the assassination.

Chief Curry’s “triple underpass” transmission occurs 6 seconds before the 12:30 time notation on Channel 2 and 2 seconds after Fisher’s “I’ll check” crosstalk. Chief Curry’s “triple underpass” transmission and the first dictabelt gunshot occur virtually at the same time. Curry’s “to the hospital” transmission occurs 12 seconds after the 12:30 time notation on Channel 2 and 18 seconds after his “triple underpass” transmission. This is key evidence because we know that Curry made the “to the hospital” transmission while still in Dealey Plaza, just after he heard gunfire. We also know that after the first hit on JFK, Secret Service agent Roy Kellerman, riding in JFK’s limo, radioed Secret Service agent Winston Lawson, who was sitting next to Curry in the lead car, and told Lawson that Kennedy was hit and ordered Lawson to go to the hospital. Thus, it is no surprise that Curry quickly gave his “to the hospital” order.


23

The final gunshot on the dictabelt occurs 2-3 seconds after the 12:30 time notation on Channel 2. All the dictabelt gunshots occur between Curry’s “triple underpass” transmission and his “to the hospital” transmission on Channel 2. As mentioned, the gunshots begin almost simultaneously with Curry’s “triple underpass” transmission. As discussed earlier, Decker’s “hold everything” crosstalk occurs on Channel 1 a split-second after the last dictabelt gunshot, but it was originally broadcast on Channel 2 about 60 seconds later. This is where we need to talk about time offsets, because the offsets suggest that Decker's crosstalk is a very unreliable time indicator. There are four time offsets between Channel 1 and Channel 2. The Decker crosstalk is the most offset of the crosstalk events; its offsets are larger than the others. Its offsets are 89 seconds and 31 seconds, whereas the Bellah offsets are 24 seconds and 3 seconds. To explain the Decker-Bellah offset, the NRC panel theorized that Channel 2’s recorder must have stopped for 31 seconds between the 12:30 and 12:32 time notations. But this seems unlikely because Channel 2 was, understandably, very busy from 12:30 onward, for several minutes, and Channel 2’s recording machine supposedly only stopped during dead spaces (i.e., when no one was talking). If we assume that the 31-second Decker-Bellah offset was caused by stylus displacement on Channel 1, instead of recorder stoppage on Channel 2, this could explain why the “hold everything” crosstalk was recorded on Channel 1 earlier than it was recorded on Channel 2. This would also mean that the “hold everything” crosstalk is worthless as a time indicator, because stylus displacement on Channel 1 put that crosstalk on Channel 1 earlier than it should have been recorded there. The stylus-displacement theory also fits well with the time notations. But if we go with the recorder-stoppage theory, this throws the 12:30-12:33 transmissions out of alignment and does not fit the time notations. The 12:32 time notation occurs almost exactly 2 minutes after the 12:30 time notation, and the 12:36 time notation comes almost exactly 6 minutes after the 12:30 time notation. But if we accept the recorder-stoppage theory, this severely skews the time notations, but we know the time notations are consistent with each other to within a few seconds.

Sound Impulses/Transmissions on Channels 1 and 2 Shortly Before and After the Assassination

Transmission/Sound Impulse Timing

12:28 time notation on Channel 1 -- Almost exactly 120 seconds before 12:30 time

notation on Channel 2

Fisher’s “I’ll check” simultaneous

crosstalk

-- 2 seconds before first dictabelt gunshot impulse

-- 8 seconds before 12:30 time notation on Channel 2

First gunshot impulse on dictabelt -- 2 seconds after Fisher’s crosstalk



24

Chief Curry’s “triple underpass”

transmission on Channel 2

-- 2 seconds after Fisher’s crosstalk


12:30 time notation on Channel 2 -- Almost exactly 120 seconds after 12:28 time

notation on Channel 1

Final gunshot impulse on dictabelt -- 2-3 seconds after 12:30 time notation on Channel 2

Chief Curry’s “to the hospital”

transmission Channel 2

-- 12 seconds after 12:30 time notation on Channel 2

-- 18 seconds after his “triple underpass”

transmission

Those who reject the acoustical evidence dismiss the gunfire timeframe indicated by the Fisher crosstalk, the time notations, and the two Curry transmissions in Dealey Plaza. Instead, they insist on using Decker's "hold everything" crosstalk as their time indicator because it gives them a basis to claim that the dictabelt gunshots occurred about 60 seconds after the assassination. It also serves as their excuse for not explaining the powerful, intricate correlations between the dictabelt gunshots and the gunshots from the Dealey Plaza test firing. Importantly, as mentioned earlier, the Fisher crosstalk is simultaneous, i.e., it occurs at the same time on Channel 1 that it does on Channel 2. This is crucial because Fisher’s “I’ll check” crosstalk comes 2 seconds before the first dictabelt shot, 2 seconds before Curry’s “triple underpass” transmission, 8 seconds before the 12:30 time notation, and 20 seconds before Curry’s “to the hospital” transmission. Thus, Fisher’s crosstalk serves as an excellent time indicator and as a way to correlate the timing of key transmissions on the two channels. It also establishes when the shots occurred in relation to the 12:30 time notation on Channel 2, Curry’s “triple underpass” transmission on Channel 2, and Curry’s “to the hospital” transmission on Channel 2. Some scholars, including Dr. Paul Hoch, have argued that the extant police tape contains indications of alteration. Other scholars have noted evidence that the police tape is a copy. The dictabelt recording that that FBI used for the transcript published by the WC is clearly not the same recording that the HSCA acoustical experts used. If the extant dictabelt tape has been altered, we would need the original recording to determine how the alterations affected the timing of the transmissions and of the other sounds. If the tape is a copy, the copying process may have altered the timing of some of the transmissions and sounds, and we would need the original recording to verify the timing of the sound impulses. Dr. Josiah Thompson’s long-awaited new book Last Second in Dallas, presents powerful evidence that the Decker “hold everything” transmission is not time synchronous, that it was recorded at a different speed than the valid crosstalk transmissions, and that it is almost certainly an overdub that occurred in the copying process. In addition, Dr. Thompson proves that the Fisher “I’ll check” transmission is genuine crosstalk that confirms that the gunshot impulse patterns on the police tape were recorded during the assassination. Dr. Thompson’s book includes separate chapters on the acoustical evidence written by Dr. Barger and by fellow BBN scientist Richard Mullen.


25

Larry Sabato’s Sonalysts Study In 2013, Larry Sabato, a political science professor at the University of Virginia, arranged for the professional services firm Sonalysts, Inc., to review the acoustical evidence. The Sonalysts report contains severe errors and repeats discredited claims, as Dr. Thomas documents in his article “Sabato, Sonalysts, and Sophistry.” For example, the Sonalysts report claims that the motorcycle with the open mike “was traveling at a high rate of speed” when JFK’s limousine was moving much more slowly during the shooting. But this claim is erroneous. During the time period in question on the dictabelt recording, the motorcycle can be heard idling. Dr. Thomas:

In point of fact, the sounds identified as the gunshots by the HSCA’s acoustical experts occur at a segment of the police recording when the motorcycle is idling along. The disconnect between reality and the perceptions, or at least the opinions stated in this new study, is breathtaking. (Thomas 2014:1)

The Sonalysts report claims that all the data that their two analysts examined “uniformly indicate that the motorcycle with the open microphone was not part of the motorcade.” But the report does not explain the intricate correlations between the gunshot impulse patterns on the dictabelt recording and the gunshot impulse patterns from the Dealey Plaza test firing. The report never gets around to explaining how gunshot impulse patterns unique to Dealey Plaza ended up on the police tape.

Another view of the grassy knoll soon after the shooting ended

In a feeble effort to explain the gunshot impulse patterns on the dictabelt tape, the Sonalysts report provides a list of white noises that “could” explain the suspect impulse patterns. But simply listing other theoretically possible sources for the impulse patterns is futile and irrelevant without also explaining the intricate correlations between the dictabelt impulse patterns and the impulse patterns from the test firing in Dealey Plaza. Yes, a burst of static can cause an impulse pattern that will resemble the graphical representation of a gunshot pattern on a spectrogram or oscillogram. However, that static is not going to include an N-wave from supersonic gunfire that is followed, at the correct interval, by a muzzle blast; and the muzzle blast is not going to be followed, at the correct interval, by muzzle-blast echoes; and, most important, a burst of static is not


26

going to contain echo-delay patterns that match echo-delay patterns of gunshots fired in Dealey Plaza. Professor Aschkenasy discussed this matter in his HSCA testimony:

Mr. EDGAR. How do you know that the squiggly lines you are looking at are really supersonic? Mr. ASCHKENASY. They are not supersonic. Those are sound waves. Those are presentations of sound waves. The question, what you might want to ask, is about whether we can tell a bullet was there, namely, was it creating a supersonic shock wave? That is what you are questioning. And those are not supersonic sound waves. Those are sound waves as recorded by a microphone, and put into electrical form by the equipment that was used to transmit it and record it, and there is nothing supersonic in those squiggles that we have up there on that board. Mr. EDGAR. Would you answer the question I wanted to ask? Mr. ASCHKENASY. Well, because you have a bullet that travels faster than sound, it will get to someplace faster than the sound reaching that same point. We are talking about two components, the bullet and the muzzle blast. The bullet flies, let's just pick a number, at 2,220 feet per second, so that it travels at twice the speed of sound for this particular example, when you fire the gun. And it flies, let's say for 200 feet. It will get at the target 200 feet away in a certain period of time. Just like a boat pushes the water ahead of it creating the V-shape wake behind the boat, that is similar to what you see in a shock wave from a bullet. And that shock wave is what is recorded by the microphone that is right next to the target. Sometime later, finally the sound catches up to it and gets to the target, and the muzzle blast is recorded. That interval of time is fixed, by the fact that you have a certain muzzle velocity and you have a certain distance, they occur in a fixed time relationship. We have also the first, it's covered by the photograph--could somebody remove that photograph, please. If I may point something out there. Mr. EDGAR. Yes. Mr. ASCHKENASY. I can point out here also these first impulses before the muzzle blast, those are the shock waves, and if you look carefully--I am sure you cannot look that carefully at that distance--but if you look at these graphs, because these microphones are located at different positions on the street, the relationship between the shock wave and the muzzle blast changes, and it changes in a predictable manner because the manner in which you expect them


27

to change is related to where the observer, or the microphone is picking up both the shock waves and the muzzle blast. Now, you measure here about on the average of about 14 milliseconds, 14 thousandths of a second delay between the shock wave and the muzzle blast. We go now here to the police tape and the measurement that we found was around 24 milliseconds here. It is now reasonable to assume because of the measured time interval that the impulse may have attributes of a shock wave. If you expand the experiment tape and take an even better look at it, you find there is a little shock wave echo right in between the shock wave and the muzzle blast, and if you expand the police tape properly, you find similar patterns, implying to us that this impulse has the qualities, attributes of a shock wave. (5 HSCA 609-610)

In a revealing criticism, the Sonalysts report argues that the HSCA acoustical scientists should have put more emphasis on the amplitude of the sound impulses, not just on their timing (pp. 14-15). This argument indicates the two Sonalysts analysts did not understand how the police dispatch system’s automatic gain control (AGC) circuit worked. The AGC did not just suppress loud sounds; it also amplified weak sounds. The Sonalysts argument also ignores the fact that windshield distortion would have reduced the strength of recorded sound impulses. Given these two factors, any amplitude measurements would be very unreliable indicators of the original amplitude of the sound impulses. Weiss and Aschkenasy explained the effects of the AGC and windshield distortion in their report:

The DPD radio dispatching system contained a circuit, that would have greatly affected the relative strengths of the recorded echoes of a muzzle blast. This circuit, the automatic gain control (AGC), limited the range of variations in the levels of signals by reducing the levels of received signals when they were too strong and increasing their levels when they were too weak. It responded very rapidly to a sudden increase in the level of a signal, but comparatively slowly to a sudden reduction in a signal level. Consequently, the response of the AGC to the sound of a muzzle blast would greatly reduce the recorded levels of echoes and background noise received shortly afterward. Progressively during the next 100 milliseconds, the AGC would allow the recorded levels of received signals to increase until full amplification was finally restored. The effect on the predicted echoes would be to make the recorded levels of late-arriving echoes very nearly the same as those of the early ones. Concurrently, the recorded background noise would gradually rise to its level before the muzzle blast was received. A different but also significant effect on the relative strengths of the recorded echoes would have been caused by the motorcycle windshield. On the DPD motorcycles, the microphone was usually mounted on a bar directly behind the windshield. Sounds arriving from the front of the motorcycle would have diffracted around the windshield and in doing so would have lost strength. As


28

determined by experiment, the windshield of a 1960's Harley Davidson motorcycle attenuated [weakened] gunshot sounds received from in front of the motorcycle by 3 decibels to 6 decibels. The amount of attenuation [weakening, decreasing] depended on how close the microphone was to the windshield. Obviously, sounds received from the sides and rear of the motorcycle would not be affected by the windshield. (8 HSCA 30-31)

Dr. Thomas:

In an effort to diminish the significance of the matches Sonalysts complained that the HSCA experts had put too much emphasis on the timing and not enough emphasis on the amplitude of the impulses. Had they included amplitude in the scoring the matches would not have been achieved. This argument rested on Sonalysts misunderstanding of the effect of automatic gain control which rendered amplitude of the impulses as unreliable. The AGC does not just suppress the amplitude of loud sounds as they argued on p. 15, but it amplifies the weak ones. The suppression of the AGC initiated by the muzzle blast has a duration of about 50 msec, so it would not have suppressed the impulses 200 msec later as Sonalysts supposed. (Thomas 2014:3)

The Grassy Knoll Shot and the Zapruder Film

Some defenders of the acoustical evidence assert that HSCA Chief Counsel Robert Blakey mismatched the impulse patterns on the tape with the Zapruder film. Under Blakey’s direction, the committee stated in its final report that the fourth shot on the tape was the fatal head shot. But some researchers maintain that if the third impulse is aligned with the head shot, then every other dictabelt impulse pattern matches an action in the Zapruder film. In fact, Robert Groden, who served as a consultant to the HSCA on certain issues, claims that he met with Weiss and Aschkenasy, and that the three of them found that the third impulse was the best match for the head shot. But, according to Groden, Blakey would not allow him to express this position in his testimony. Matthew Smith:

Said Groden, "In all likelihood, the fatal shot did not come from the Book Depository, but rather from the grassy knoll; whether or not Lee Oswald was firing, someone else had actually killed the President." He went on to describe how when the fourth shot was matched up to the pictures of the President's head "exploding," none of the other shots were in alignment with the [Zapruder] film. But when the third shot was advanced to match up with those pictures "every other impulse matched an action on the film exactly." In High Treason, Groden recounted how Professor Blakey took him aside and ordered him not to express to the Committee any conclusions that he had drawn from his study of the film and tapes. The Congressmen (and the world) were to be told that the fatal shot came from the rear, and the fourth shot was the only one to be considered the head shot. (Smith 147, original emphasis)


29

Five Gunshots on the Dictabelt Tape?

The 140.3 impulse pattern on the police tape was eventually ruled to be a false alarm. However, this impulse pattern was rejected for questionable reasons. Dr. Thomas explains:

The final report of the HSCA states that there were four acoustically identified gunshots on the DPD recording. But as the above section explained, and as appears in the data tables in the technical reports, the BBN experts had identified five suspect patterns and all five had matched to the test shots in Dealey Plaza. One of the patterns was swept under the rug because the Chief Counsel for the HSCA felt the acoustical evidence would be more convincing if the acoustical results had a better fit to the Warren Commission’s finding of three shots from the Book Depository. Four of the suspect patterns had matched to test shots fired from the Book Depository in BBN’s field test (Table 2).

Reference to Table 2 shows that five patterns passed the echo delay matching test. The five patterns are identified by their chronological position: 137.70, 139.27, 140.32, 145.15, and 145.61 seconds after the beginning of the motorcycle segment. One of the five, the pattern at 140.32 sec was judged to be a false alarm and discarded. This was the one glaring error in the acoustical analysis. The BBN Report states,

"The entry in Table II that occurred at 140.32 sec is a false alarm, because it occurred only 1.05 sec later than earlier correlations also obtained from the TSBD. The rifle cannot be fired that rapidly. Since there are three correlations plausibly indicating the earlier shot, the one occurring 1.05 sec later must be a false alarm."

The logic of this statement is that if it didn’t come from Lee Harvey Oswald’s rifle then, it was not a shot. But of course, the whole purpose of the inquiry was to test the Warren Commission’s single assassin theory against the facts, not the other way around. The fifth shot was dismissed because five shots were less palatable to the committee members than four shots. Palatability is not, however, a scientific criterion for judging the validity of evidence.

Moreover, it was illogical to dismiss the pattern at 140.32 as a false positive because it was too close to the previous shot. The first two putative shots are only 1.7 sec apart, also too close together to have been fired from Lee Harvey Oswald’s rifle. If the subject sounds are the assassination gunfire, and if three of the shots are attributable to Oswald’s rifle, then the second pattern is the rogue shot, not the third. But, the second pattern, at 139.27 sec, could not be dismissed as a false alarm because it was supported by multiple correlations, including a robust correlation coefficient of 0.8. The weakest supported pattern was the pattern at 140.32, with a score of only 0.6, and only one match, and was thus selected as the “false alarm.”


30

The fact remains that five candidate patterns passed the initial screening tests, and all five matched to a significant degree with the test shot patterns. The time intervals between these putative shots, corrected for tape speed, were: 1.7, 1.1, 4.6 and 0.7 sec. (Thomas, “Overview and History,” part 2)

We must remember that the HSCA, possibly at Blakey’s direction, limited the test shots in the Dealey Plaza test firing to the sixth-floor window that Oswald allegedly used and to one spot on the grassy knoll. No test shots were fired from any of the other locations that had long been suggested by researchers as possible firing positions, such as the Dal-Tex Building and the County Records Building. Christopher Scally explains:

The HSCA's decision to conduct test firings from the Book Depository and the knoll alone had serious repercussions, because in ignoring other possible firing points, they ruled out the likelihood that any of the unmatched sounds on the police radio tape could be impulses caused by shots from other locations such as, for example, the Dal-Tex building. (Scally 35)

Yet, in spite of these limitations, at least four (and arguably five) gunshot impulse patterns from the test-firing shots match impulse patterns on the dictabelt recording.

A Summary of the Acoustical Evidence

Here are the major points of the acoustical evidence:

* At least four sets of gunshot impulse patterns with echo patterns unique to Dealey Plaza occur on the dictabelt recording. * Those echo patterns occur in the correct topographic order, which is an amazing correlation all by itself. * The echo patterns indicate that the microphone (i.e., the motorcycle with the stuck mike) was moving at nearly the same average speed at which we know JFK’s limousine was moving on Elm Street. The open-mike motorcycle was moving at an average speed of 11.7 mph during the shooting. The limousine was moving at an average speed of 11.3 mph on Elm Street.


31

* The dictabelt contains N-waves from supersonic rifle fire, and those N-waves occur only among the identified gunshot impulse patterns, and only in the two impulse patterns that were recorded when the motorcycle’s microphone was in position to record them. * The dictabelt not only contains N-waves but it also contains muzzle blasts and muzzle-blast echoes, and those N-waves, muzzle blasts, and muzzle-blast echoes occur in the correct order and interval. * Windshield distortions occur in the dictabelt's gunshot impulse patterns when they should and do not occur when they should not.

----------------------------------------------------------------


32

Bibliography

Chambers, G. Paul, Head Shot: The Science Behind the JFK Assassination, Amherst, New York: Prometheus Books, 2010.

Committee on Ballistic Acoustics, Report of the Committee on Ballistic Acoustics, National Academies Press, 1982. This is the NRC panel’s report.

Cornwell, Gary, Real Answers: The John F. Kennedy Assassination, Spicewood, Texas: Paleface Press, 1998.

Groden, Robert and Harrison Edward Livingstone, High Treason: The Assassination of President Kennedy and the New Evidence of Conspiracy, Berkley Edition, New York: Berkley Books, 1990.

House Select Committee on Assassinations, Hearings before the Select Committee on Assassinations, 12 volumes, Washington, DC: Government Printing Office, 1978-1979. “2 HSCA 10,” for example, refers to volume 2, page 10, of the HSCA hearings and exhibits.

-----, Report of the Select Committee on Assassinations, Washington, DC: Government Printing Office, 1979. Cited as “HSCA report.”

Livingstone, Harrison Edward, Killing the Truth: Deceit and Deception in the JFK Case, New York: Carroll & Graf Publishers, 1993.

Marsh, W. Anthony, "The Ramsey Report," Dateline: Dallas, volume 1, numbers 2 and 3, Summer/Fall 1992, pp. 14-16.

Moore, Jim, Conspiracy of One, Ft. Worth: The Summit Group, 1991.

Olsen, Charles and Scott Martin, Analysis of the Dallas Police Department Dictabelt Recording related to the Assassination, Sonalysts, Inc., 2013.

of President John F. Kennedy

Posner, Gerald, Case Closed: Lee Harvey Oswald and the Assassination of JFK, New York: Random House, 1993.

Scally, Christopher, "So Near . . . And Yet So Far": The House Select Committee on Assassinations' Investigation into the Murder of President John F. Kennedy, Dallas, Texas: JFK Assassination Information Center, April, 1980.

Scheim, David S., The Mafia Killed President Kennedy, London, England: Virgin Publishing Ltd, 1992. First published under the title Contract on America: The Mafia


33

Murder of President John F. Kennedy, New York: Shapolsky Publishers, 1988. The retitled 1992 edition is a revised and updated version of the 1988 original.

Smith, Matthew, JFK: The Second Plot, London: Mainstream Publishing, 1992.

Thomas, Donald, “Debugging Bugliosi,” https://www.maryferrell.org/pages/Essay_-_Debugging_Bugliosi.html.

-----, Hear No Evil: Politics, Science, and the Forensic Evidence in the Kennedy Assassination, Kindle Edition, Skyhorse, 2013.

-----, “Overview and History of the Acoustical Evidence in the Kennedy Assassination Case,” part 1: https://www.maryferrell.org/pages/Essay_-_Acoustics_Overview_and_History.html, part 2: https://www.maryferrell.org/pages/Essay_-_Acoustics_Overview_and_History_-_part_2.html, part 3: https://www.maryferrell.org/pages/Essay_-_Acoustics_Overview_and_History_-_part_3.html.

-----, “Sabato, Sonalysts, and Sophistry,” 2014, https://www.maryferrell.org/pages/Essay_-_Sabato_Sonalysts_Sophistry.html.

Thompson, Josiah, Last Second in Dallas, University Press of Kansas, 2021.

Trask, Richard, Pictures of the Pain: Photography and the Assassination of President Kennedy, Danvers, Massachusetts: Yeoman Press, 1994.



https://www.maryferrell.org/pages/Essay_-_Acoustics_Overview_and_History.html

https://www.maryferrell.org/pages/Essay_-_Acoustics_Overview_and_History.html

https://www.maryferrell.org/pages/Essay_-_Acoustics_Overview_and_History_-_part_2.html




https://www.maryferrell.org/pages/Essay_-_Sabato_Sonalysts_Sophistry.html


34

Appendix A

"Study Backs Theory of 'Grassy Knoll': New Research Puts Chance of Second JFK Gunman at 96%"

By George Lardner Jr.

THE WASHINGTON POST

March 26, 2001 - The House Assassinations Committee may have been right after all: There was

a shot from the grassy knoll.

That was the key finding of the congressional investigation that concluded 22 years ago that

President John F. Kennedy's murder in Dallas in 1963 was "probably ... the result of a

conspiracy." A shot from the grassy knoll meant that two gunmen must have fired at the

president within a split-second sequence. Lee Harvey Oswald, accused of firing three shots at

Kennedy from a perch at the Texas School Book Depository, could not have been in two places

at once.

A special panel of the National Academy of Sciences subsequently disputed the evidence of a

fourth shot, contained on a police dictabelt of the sounds in Dealey Plaza that day. The panel

insisted it was simply random noise, perhaps static, recorded about a minute after the shooting

while Kennedy's motorcade was en route to Parkland Hospital.

A new, peer-reviewed article in Science & Justice, a quarterly publication of Britain's Forensic

Science Society, says the NAS panel's study was seriously flawed. It says the panel failed to take

into account the words of a Dallas patrolman that show the gunshot-like noises occurred "at the

exact instant that John F. Kennedy was assassinated."

In fact, the author of the article, D.B. Thomas, a government scientist and JFK assassination

researcher, said it was more than 96 percent certain that there was a shot from the grassy knoll to

the right of the president's limousine, in addition to the three shots from a book depository

window above and behind the president's limousine.

HOUSE INVESTIGATOR SEES VINDICATION

G. Robert Blakey, former chief counsel to the House Assassinations Committee, said the NAS

panel's study always bothered him because it dismissed all four putative shots as random noise -

even though the three soundbursts from the book depository matched up precisely with film of

the assassination and other evidence such as the echo patterns in Dealey Plaza and the speed of

Kennedy's motorcade.

"This is an honest, careful scientific examination of everything we did, with all the appropriate

statistical checks," Blakey said of Thomas's work. "It shows that we made mistakes, too, but

minor mistakes. The main thing is when push comes to shove, he increased the degree of

confidence that the shot from the grassy knoll was real, not static. We thought there was a 95

http://www.washingtonpost.com/


35

percent chance it was a shot. He puts it at 96.3 percent. Either way, that's 'beyond a reasonable

doubt.' "

The sounds of assassination were recorded at Dallas police headquarters when a motorcycle

patrolman inadvertently left his microphone switch in the "on" position, deluging his

transmitting channel with what seemed to be motorcycle noise. Using sophisticated techniques, a

team of scientists enlisted by the House committee filtered out the noise and came up with

"audible events" within a 10-second time frame that it believed might be gunfire.

The Warren Commission had concluded in 1964 that only three shots, all from behind, all from

Oswald's rifle, were fired in Dealey Plaza as the motorcade passed through. But the House

experts, after extensive tests, found 10 echo patterns that matched sounds emanating from the

grassy knoll, traveling carefully measured distances to nearby buildings and then bouncing off

them to hit the open motorcycle transmitter.

They also placed the unknown gunman behind a picket fence at the top of the grassy knoll, in

front of and to the right of the presidential limousine. The House committee concluded that this

shot missed, and that Kennedy was killed by a final bullet from Oswald's rifle. Thomas, by

contrast, believes it was the shot from the knoll, seven-tenths of a second earlier, that killed the

president.

MISALIGNED AUDIO CHANNELS

The NAS panel, assigned to conduct further studies after the committee closed down, said in

1982 that the noises on the tape previously identified as gunshots "were recorded about one

minute after the president was shot."

The NAS experts, headed by physicist Norman F. Ramsey of Harvard, reached that conclusion

after studying the sounds on the two radio channels Dallas police were using that day. Routine

transmissions were made on Channel One and recorded on a dictabelt at police headquarters. An

auxiliary frequency, Channel Two, was dedicated to the president's motorcade and used

primarily by Dallas Police Chief Jesse Curry; its transmissions were recorded on a separate Gray

Audograph disc machine.

The shooting took place within an 18-second interval that began with Curry in the lead car

announcing on Channel Two that the motorcade was approaching a triple underpass and ended

with the chief stating urgently: "Go to the hospital." What seemed to be the gunshots were

picked up on Channel One during that interval.

The NAS panel pointed out that Dallas County Sheriff Bill Decker could be heard on both

channels saying, "... Hold everything secure ..." seemingly about a half-second after the last

gunshot on Channel One. Curry had already told everyone on Channel Two a minute earlier to

go to the hospital. As a result, the Ramsey panel concluded that the supposed gunshot noises

came "too late to be attributed to assassination shots."


36

What actually happened was that Curry issued his "go to the hospital" order right after the first

shots were fired, wounding Kennedy and Texas Gov. John Connally. The final bullet was fired in

almost the same instant that Curry uttered his command. A minute later, Decker, riding in the

same car with Curry, grabbed the mike and issued his orders to "hold everything secure."

SEVERAL ERRORS CITED

The study's author said the chances that the National Academy of Science's single-gunman

theory was correct were 1 in 100,000.

The NAS experts made several errors, Thomas said, but their biggest mistake was in using

Decker's words to line up the two channels. They ignored a much clearer instance of cross talk

when Dallas police Sgt. S. Q. Bellah can be heard on both channels, asking: "You want me to

hold this traffic on Stemmons until we find out something, or let it go?"

Those remarks come 179 seconds after the last gunshot on Channel One and 180 seconds after

Curry's order to "go to the hospital" on Channel Two. When Bellah's words are used to line up

the two channels, Thomas found, the gunshot sounds "occur at the exact instant that John F.

Kennedy was assassinated."

How is it, then, that Decker's remarks on Channel One come a full minute after Curry's on

Channel Two and yet a half-second after the last gunshot on Channel One?

"It's a misplaced bit of speech," Thomas said in an interview. "An overdub. The recording needle

for Channel One probably jumped. You can hear Decker giving a whole set of instructions on

Channel Two, but on Channel One, you get only a fragment, '... hold everything secure. ... ' "

According to Thomas, the NAS panel made other mistakes: in calculating the position of the

grassy knoll shooter, in fixing the time of that shot and in stating the Channel Two recorder had

stopped when it hadn't. In all, Thomas said, the chances of the NAS panel having been right were

1 in 100,000.

House committee experts James Barger, Mark Weiss and Eric Aschkenasy, have always held

firm to their findings of a shot from the knoll. Similarly, Ramsey, as chairman of the NAS panel,

said last weekend that he was "still fairly confident" of his group's work, but he said he wanted to

study the Science and Justice article before making further comment. He said he did not recall

the Bellah cross talk.

Thomas's article can be found at the following address:

http://JFKlancer.com/pdf/Thomas.pdf (Requires Adobe Acrobat Reader)

Visit THE WASHINGTON POST online at http://www.washingtonpost.com/.

http://jfklancer.com/pdf/Thomas.pdf




37

Appendix B

Extract from the HSCA’s final report:

(2) Weiss-Aschkenasy analysis -- In mid-September 1978, the committee asked Weiss and Aschkenasy, the acoustical analysts who had reviewed Barger's work, if they could go beyond what Barger had done to determine with greater certainty if there had been a shot from the grassy knoll. Weiss and Aschkenasy conceived an analytical extension of Barger's work that might enable them to refine the probability estimate.(45) They studied Dealey Plaza to determine which structures were most got to have caused the echoes received by the microphone in the 1978 acoustical reconstruction that had recorded the match to the shot from the grassy knoll. They verified and refined their identifications of echo-generating structures by examining the results of the reconstruction. And like BBN, since they were analyzing the arrival time of echoes, they made allowances for the temperature differential, because air temperature affects the speed of sound.(46) Barger then reviewed and verified the identification of echo-generating sources by Weiss and Aschkenasy.(47)

With respect to the other shots, Barger estimated there was an 88 percent chance that impulse pattern one represented a shot from the book depository (based on three matches), 88 percent again for impulse pattern two (three matches) and a 75 percent chance that impulse pattern four represented a shot from the depository (two matches).(43) At the time of his testimony in September 1978, Barger estimated that the probability of all four impulses actually representing gunshots was only 29 percent.(44)

Page 73

Once they had identified the echo-generating sources for a shot from the vicinity of the grassy knoll and a microphone located near the point indicated by Barger's tests, it was possible for Weiss and Aschkenasy to predict precisely what impulse sequences (sound fingerprints) would have been created by various specific shooter and microphone locations in 1963.(48) (The major structures in Dealey Plaza in 1978 were located as they had been in 1963.) Weiss and Aschkenasy determined the time of sound travel for a series of sound triangles whose three points were shooter location, microphone location and echo-generating structure location. While the location of the structures would remain constant, the different combinations of shooter and microphone locations would each produce a unique sound travel pattern, or sound fingerprint.(49) Using this procedure, Weiss and Aschkenasy could compare acoustical fingerprints for numerous precise points in the grassy knoll area with the segment identified by Barger on the dispatch tape as possibly reflecting a shot fired from the knoll.(50)

Because Weiss and Aschkenasy could analytically construct what the impulse sequences would be at numerous specific shooter and microphone locations, they decided to look for a match to the 1963 police dispatch tape that correlated to within ±1/1.000 of a second, as opposed to +-6/1.000) of a second, as Barger had done.(51) By looking for a match with such precision, they considerably reduced the possibility


38

that any match they found could have been caused by random or other noise,(52) thus substantially reducing the percentage probability of an invalid match.

Weiss and Aschkenasy initially pinpointed a combination of shooter-microphone locations for which the early impulses in pattern three matched those on the dispatch tape quite well, although later impulses in the pattern did not. Similarly, they found other microphone locations for which later impulses matched those on the dispatch tape, while the earlier ones did not. They then realized that, a microphone mounted on a motorcycle or other vehicle would not have remained stationary during the period it was receiving the echoes. They computed that the entire impulse pattern or sequence of echoes they were analyzing on the dispatch tape occurred over approximately three-tenths of a second, during which time the motorcycle or other vehicle would have, at 11 miles per hour, traveled about five feet. By taking into account the movement of the vehicle. Weiss and Aschkenasy were able to find a sequence of impulses representing a shot from the grassy knoll in the reconstruction that matched both the early and late impulses on the dispatch tape.(53)

Approximately 10 feet from the point on the grassy knoll that was picked as the shooter location in the 1978 reconstruction and four feet from a microphone location which, Barger found, recorded a shot that matched the dispatch tape within +-6/1,000 of a second, Weiss and Aschkenasy found a combination of shooter and microphone locations they needed to solve the problem. It represented the initial position of a microphone that would have received a series of impulses matching those on the dispatch tape to within +-1/1.000 of a second. The microphone would have been mounted on a vehicle that was moving along the motorcade route at 11 miles per hour.

Weiss and Aschkenasy also considered the distortion that a windshield might cause to the sound impulses received by a motorcycle microphone. They reasoned that the noise from the initial muzzle blast of a shot would be somewhat muted on the tape if it traveled through the windshield to the microphone. Test firings conducted under the auspices of the New York City Police Department confirmed this hypothesis. Further, an examination of the dispatch tape reflected similar distortions on shots one, two, and three, when the indicated positions of the motorcycle would have placed the windshield between the shooter and the microphone. On shot four, Weiss and Aschkenasy found no such distortion.(55) The analysts' ability to predict the effect of the windshield on the impulses found on the dispatch tape, and having their predictions confirmed by the tape, indicated further that the microphone was mounted on a motorcycle in Dealey Plaza and that it had transmitted the sounds of the shots fired during the assassination.

Weiss and Aschkenasy examined only the impulse sequence that Barger indicated had come from the grassy knoll. Due to time constraints, they did not analyze the three impulse sequences indicating shots fired from the Texas School Book Depository.

Page 74


39

Since Weiss and Aschkenasy were able to obtain a match to within +-1/1,000 of a second, the probability that such a match could occur by random chance was slight. Specifically, they mathematically computed that, with a certainty factor of 95 percent or better, there was a shot fired at the Presidential limousine from the grassy knoll.(56)

Barger independently reviewed the analysis performed by Weiss and Aschkenasy and concluded that their analytical procedures were correct.(57) Barger and the staff at BBN also confirmed that there was a 95 percent chance that at the time of the assassination a noise as loud as a rifle shot was produced at the grassy knoll. When questioned about what could cause such a noise if it were not a shot, Barger noted it had to be something capable of causing a very loud noise--greater than a single firecracker.(58) Further, given the echo patterns obtained, the noise had to have originated at the very spot behind the picket fence on the grassy knoll that had been identified,(59) indicating that it could not have been a backfire from a motorcycle in the motorcade.(60)

In addition, Barger emphasized, the first part of the sequence of impulses identified as a shot from the grassy knoll was marked by an N-wave, a characteristic impulse caused by a supersonic bullet.(61) The N-wave, also referred to as a supersonic shock wave, travels faster than the noise of the muzzle blast of a gun and therefore arrives at a listening device such as a microphone ahead of the noise of a muzzle blast. The presence of the N-wave was, therefore, a significant additional indication that the third impulse on the police dispatch tape represented gunfire, and, in particular, a supersonic bullet.(62) The weapon may well have been a rifle, since most pistols except for some such as a .44 magnum--fire subsonic bullets. The N-wave was further substantiation for a finding that the third impulse represented a shot fired in the direction of the President. Had the gun been discharged when aimed straight up or down, or away from the motorcade, no N-wave would have appeared.(63) Of the impulse patterns on the dispatch tape that indicated shots from the book depository, those that would be expected to contain an N-wave, given the location of the vehicle's microphone, did so, further corroborating the conclusion that these impulses did represent supersonic bullets.(64)

The motorcycle was traveling 120 feet behind the Presidential limousine when the shots were fired. This put shots one and two from the book depository, as well as shot three from the grassy knoll, in front of the motorcycle windshield.

Page 75

When questioned about the probability of the entire third impulse pattern representing a supersonic bullet being fired at the President from the grassy knoll, Barger estimated there was a 20 percent chance that the N-wave, as opposed to the sequence of impulses following it, was actually caused by random noise.(65) Accordingly, the mathematical probability of the entire sequence of impulses actually representing a supersonic bullet was 76 percent, the product of a 95 percent chance that the impulse pattern represented noise as loud as a rifle shot from the grassy knoll times an 80 percent chance that the N-wave was caused by a supersonic bullet.(66)


40

The committee found no evidence or indication of any other cause of noise as loud as a rifle shot coming from the grassy knoll at the time the impulse sequence was recorded on the dispatch tape, and therefore concluded that the cause was probably a gunshot fired at the motorcade.

Search for a motorcycle.---As the work of Weiss and Aschkenasy produced strong indications of a shot from the grassy knoll, the committee began a search of documentary and photographic evidence to determine if a motorcycle or other vehicle had been in the locations indicated by the acoustical tests.

Earlier in its investigation, the committee had interviewed many Dallas police officers who had ridden in the presidential motorcade, although the purpose of the interviews was not to determine the location of a motorcycle that might have had its radio transmitting switch stuck in the "on" position. Among the officers who were interviewed, one who subsequently testified in a public hearing was H.B. McLain. In his interview on September 26, 1977, McLain said that he had been riding to the left rear of Vice President Johnson's car and that just as he was completing his turn from Main onto Houston Street, he heard what he believed to have been two shots.(67) Sergeant Jimmy Wayne Courson was also interviewed on September 26. 1977. He stated that his assignment in the motorcade was in front of the press bus, approximately six or seven cars to the rear of the presidential limousine, and that as he turned onto Houston Street, he heard three shots about a second apart.(68) Neither officer was asked specifically whether his radio was on channel one or two, or whether his microphone switch might have been stuck in the transmit position.

The committee obtained Dallas Police Department assignment records confirming that McLain and Courson had both been assigned to the left side of the motorcade, (69) and it discovered photographic evidence(70) that Courson was riding to the rear of McLain, and as Courson recalled,(71) he was in the vicinity of the press bus. The available films revealed that throughout the motorcade the spacing of the motorcycles varied, but that McLain was generally several car lengths ahead of Courson and therefore much closer to the presidential and Vice Presidential limousines.(72) No photographs of the precise locations of the two officers at the moment of the assassination were, at that time, found. Photographs taken shortly before the assassination, however, did indicate that McLain was on Houston Street heading toward Elm as the presidential limousine was turning onto Elm in front of the Texas School Book Depository.(73) At the time of the assassination, therefore, he would have been in the approximate position of the transmitting microphone, as indicated by the acoustical analysis.

Subsequent to the committee's final vote on its findings, additional photographic evidence of the actions of Officer McLain was received by the committee from Robert Groden, a consultant to the committee.(74) It supported the committee's conclusion with respect to McLain's testimony, but since it was not received until after the vote, it was not relied upon in this report.

Page 76


41

The committee reviewed transcripts of the Dallas police dispatch tapes for both channel one and channel two. It did not find any voice transmissions from McLain on either channel on November 22, 1963.(As noted, it was determined that the shots fired during the assassination were recorded over channel one. If it could have been established that McLain was transmitting over channel two, then the gunfire transmissions could not have come from his motorcycle radio.)

McLain was asked by the committee to come to Washington to testify. He was shown all of the photographic evidence that the committee had assembled, as well as the Dallas police records of the motorcade assignments. McLain testified before the committee on December 29, 1978, that he was assigned to ride on the left side of the motorcade; that since he would slow down at corners, often stopping momentarily, and then speed up during straight stretches, his exact, position in the motorcade varied; and that he was the first motorcycle to the rear of the Vice presidential limousine.(75)

He further stated that he was the officer in the photographs taken of the motorcade on Main and Houston Streets, and that at the time of the assassination he would have been in the approximate position of the open microphone near the corner of Houston and Elm, indicated by the acoustical analysis.(76) He did not recall using his radio during the motorcade nor what channel it was tuned to on that day.(77) He stated it unusually was tuned to channel one.(78) The button on his transmitter receiver, he acknowledged, often got stuck in the "on" position when he was unaware of it, but he did not know if it was stuck during the motorcade.(79)

McLain testified before the committee that he recalled hearing only one shot and that he thereafter heard Chief Curry say to go to the hospital.(80) McLain testified it was possible that he heard the broadcast of Chief Curry (which would have been on channel two) over the speaker of his own radio, or over the speaker of the radio of another motorcycle.(81)

Following the hearing, the committee secured a copy of the daily assignment sheet for motorcycles from the Dallas Police Department and found that McClain had been assigned motorcycle number 352 and call sign 155 on November 22, 1963.(82) Preliminary photographic enhancement of the films taken on Houston and Main Streets indicated that the number on the rear of the motorcycle previously identified as having been ridden by McLain was, in fact, 352.(83)

During his public testimony, McLain also identified photographs of motorcycles on Elm Street (JFK Exhibit F-675) and at Parkland Hospital (JFK Exhibits 674, 676, 677, and 678) as possibly portraying his motorcycle. Of the pictures at Parkland Hospital (JFK Exhibit F-674) apparently indicates that the microphone button was turned to channel one. With respect to the photograph on Elm Street, McLain stated that the other motorcycle in the picture appeared to be ridden by Sergeant Courson. At that time, counsel cautioned that the photographs were being introduced for a limited purpose, since they had not been analyzed by any photographic experts; it was unclear if the cycle in each photograph was that of McLain; and the channel selector, even if it was on


42

channel one, could have been switched after the shots were fired. Preliminary photographic analysis of those pictures conducted by one expert in the time available after the hearing cast doubt upon the accuracy of at least McLain's identification of Courson in Exhibit F-675, and indicated that the channel selector on the motorcycle in Exhibit F-674 may have been on channel two instead of one. because the committee was unable to conduct comprehensive and thorough analyses of those photographs, it did not rely on Exhibits F-674, F-675, F-676, F-677 or F-678 in forming any conclusions.

Page 77

The committee recognized that its acoustical analysis first established and then relied on the fact that a Dictabelt had recorded transmissions from a radio with a stuck microphone switch located in Dealey Plaza. The committee realized that the authenticity of the tape and the location of the stuck microphone were both of great importance to the acoustical analysis. Consequently, it sought to verify that the tape in fact contained a broadcast from an open motorcycle microphone in Dealey Plaza during the assassination.

The findings of the acoustics experts may be challenged by raising a variety of questions, questions prompted, for example, by the sound of sirens on the tape,(84) by statements by Officer McLain subsequent to his hearing testimony in which he denied that it was his radio that was transmitting, (85)"by what appears to be the sound of a carillon bell on the tape, (86) and by the apparent absence of crowd noise. The committee carefully considered these questions as they bore on the authenticity of the tape and the location of the stuck microphone.

Approximately 2 minutes after the impulse sequences that, according to the acoustical analysis, represent gunfire, the dispatch tape contains the sound of sirens for approximately 40 seconds. The sirens appear to rise and then recede in intensity, suggesting that the position of the microphone might have been moving closer to and then farther away from the sirens, or that the sirens were approaching the microphone and then moving away from it.(87)

If the sirens were approaching the microphone and then moving away from it, it could be suggested that the motorcycle with the stuck transmitter was stationary on the Stemmons Freeway and not in Dealey Plaza. The sirens would appear to increase and then decrease as some vehicles in the motorcade, with their sirens turned on, drove along the freeway on the way to Parkland Hospital, approaching and then passing by the motorcycle with the stuck microphone. According to a transcript of channel two transmissions, approximately 3 1/2 minutes after the assassination Dallas Police Department dispatcher Gerald D. Henslee stated that an unknown motorcycle on Stemmons Freeway appeared to have its microphone switch stuck open on channel one.(88) The committee interviewed Henslee on August 12, 1978. He told the committee he had assumed the motorcycle was on the freeway from the noise of the sirens.(89) Other Dallas police officers have also speculated that the motorcycle may have been standing near the Trade Mart.


43

Officer McLain's acknowledged actions subsequent to the assassination might explain the sound of sirens on the tape. McLain was in fact probably on Stemmons Freeway at the time Henslee noted that an unknown motorcycle appeared to have its microphone switch stuck open. McLain himself testified that following the assassination, he sped up to catch the front cars of the motorcade that had entered Stemmons Freeway en route to Parkland Hospital.(90) In any event, it is certain he left the plaza shortly after the assassination. The cars in the motorcade had their sirens on, and this could account for the sound of the sirens increasing as McLain drew closer to them, whether he left Dealey Plaza immediately or shortly after the assassination.

McLain's microphone was so constructed that it would pick up only the siren of the motorcycle on which it was mounted or one of a motorcycle or other vehicle that was not more than 300 feet away.

Page 78

Subsequent to his hearing testimony, McLain stated that he believed he turned on his siren as soon as he heard Curry's order to proceed to Parkland Hospital. He said that everyone near him had their sirens on immediately.(91) Should his memory be reliable, the broadcast of the shots during the assassination would not have been over his radio, because the sound of sirens on the tape does not come until approximately 2 minutes later. The committee believed that McLain was in error on the point of his use of his siren. Since those riding in the motorcade near Chief Curry had their sirens on, there may have been no particular need for McLain to turn his on, too. The acoustical analysis pinpointing the location of the microphone, the confirmation of the location of the motorcycle by photographs, his own testimony as to his location, and his slowing his motorcycle as it rounded the corner of Houston and Elm (as had been previously indicated by the acoustical analysis),(92) and the likelihood that McLain did not leave the plaza immediately, but legged behind momentarily after the assassination, led the committee to conclude it was Officer McLain whose radio microphone switch was stuck open.

Further, the committee noted, it would have been highly improbable for a motorcycle on Stemmons Freeway to have received the echo patterns for the four impulses that appear on the dispatch tape. As noted in more detail below, to contend that the microphone was elsewhere carries with it the burden of explaining all that appears on the tape. To be sure, those who argue the microphone was in Dealey Plaza must explain the sounds that argue it was not. Similarly, those who contend it was not in Dealey Plaza must explain the sounds that indicate it was. As Aschkenasy testified, the echo patterns on the tape would only have been received by a microphone located in a physical environment with the same acoustical characteristics as Dealey Plaza.(93) It is extremely unlikely that the echo patterns on the tape, if received from elsewhere, would so closely parallel the echo patterns characteristic of Dealey Plaza.

The tape contains the faint sound of a carillon-like bell about 7 seconds after the last impulse believed to have been a shot, but no such bell was known to have been in the


44

vicinity of Dealey Plaza. Accordingly, the possibility that the motorcycle with the stuck radio transmitter might not have been in Dealey Plaza was considered. The committee found that the radio system used by the Dallas Police Department permitted more than one transmitter to operate at the same time, and this frequently occurred.(94) The motorcycle whose radio transmitted the sound of a bell was apparently not positioned in Dealey Plaza, but this did not mean that the transmissions of gunshots were also from a radio not in Dealey Plaza. The logical explanation was that the dispatch tape contains the transmissions of two or more radios.(95)

The absence of identifiable crowd noise on the tape also might raise questions as to whether the motorcycle with the stuck transmitter was in Dealey Plaza. The lack of recognizable crowd noise, however, may be explained by the transmission characteristics of the microphone.

Page 79

Dallas police motorcycle. radios were equipped with a directional microphone and were designed to transmit only very loud sounds. A human voice would transmit only if it originated very close to the front of the mike. The chief objective of this characteristic was to allow a police officer, when speaking directly into the microphone, to be heard over the sound of his motorcycle engine. Background noise, such as that of a crowd, would not exceed the noise level from the much closer motorcycle engine, and it would not be identifiable on a tape of the radio transmission. The sound of a rifle shot is so pronounced, however, that it would be picked up even if it originated considerably farther away from the microphone than other less intense noise sources, such crowd.(96)

(c) Other evidence with respect to the shots

To address further the question of whether the dispatch tape contained sounds from a microphone in Dealey Plaza with a stuck transmitting switch, the committee reviewed independent evidence. It reasoned that if the timing, number and location of the shooters, as shown on the tape, were corroborated or independently substantiated in whole or in part by other scientific or physical evidence--that is, the Zapruder film, findings of the forensic pathology and firearms panels, the neutron activation analysis and the trajectory analysis--the validity of the acoustical analysis and the authenticity of the tape could be established. Conversely, any fundamental inconsistency in the evidence would undermine the analysis and the authenticity of the tape.

The tape and acoustical analysis indicated that, in addition to the shot from the knoll, there were three shots fired at President Kennedy from the Texas School Book Depository. This aspect of the analysis was corroborated or independently substantiated by three cartridge cases found on the sixth floor of the Texas School Book Depository on November 22, 1963, cartridge cases that had been fired in Oswald's rifle,(97) along with other evidence related to the number of shots fired from Oswald's


45

rifle. This corroboration was considered significant by the committee, since it tended to prove that the tape did indeed record the sounds of shots during the assassination.

Further corroboration or substantiation was sought by correlating the Zapruder film to the acoustical tape. The Zapruder film contains visual evidence that two shots struck the occupants of the Presidential limousine.(98) The committee attempted to correlate the observable reactions of President Kennedy and Governor Connally in the film to the time spacing of the four impulses found in the recording of the channel one transmission. The correlation between the film and the recording however, could only be approximate because it was based on the estimated real-time characteristics of the recording (calculated from the frequent time annotations made by the dispatcher) (99) and the average running time of the film (between 18.0 and 18.5, or an average of 18.3 frames per second). (pp. 72-79)

-------------------------------------------

ABOUT THE AUTHOR: Michael T. Griffith holds a Master’s degree in Theology from The Catholic Distance University, a Graduate Certificate in Ancient and Classical History from American Military University, a Bachelor’s degree in Liberal Arts from Excelsior College, and two Associate in Applied Science degrees from the Community College of the Air Force. He also holds an Advanced Certificate of Civil War Studies and a Certificate of Civil War Studies from Carroll College. He is a graduate in Arabic and Hebrew of the Defense Language Institute in Monterey, California, and of the U.S. Air Force Technical Training School in San Angelo, Texas. In addition, he has completed Advanced Hebrew programs at Haifa University in Israel and at the Spiro Institute in London, England. He is the author of five books on Mormonism and ancient texts, including How Firm A Foundation, A Ready Reply, and One Lord, One Faith. He is also the author of a book on the JFK assassination titled Compelling Evidence (JFK Lancer, 1996). Back to JFK Assassination Web Page

mailto:[email protected]

http://www.mtgriffith.com/index.php?p=1_6

proof of a second gunman in the jfk assassination

Documents