In December, 1976, Gary Mack, the program director at KFJZ-FM radio in Fort Worth, Texas, met with Penn Jones, Jr., the editor of the small town Midlothian Mirror newspaper and a leading conspiracy theorist. Mack, who first became interested in the assassination after the March, 1975, ABC television broadcast of the Zapruder film, later wrote, “We were discussing exactly how the assassination occurred. He mentioned to me that radio communications on one of two police channels (actually the main channel) were blocked for five straight minutes beginning just a few seconds before the shots were fired. Most of the Dallas officers were on Channel One, including the officers in the President’s motorcade. Several officials and others in the procession were on the second channel, but most of the activity was on channel one. Penn was of the opinion that the communications were jammed on purpose… I asked Penn how this interference occurred. He said apparently someone had left his microphone key depressed and it blocked the channel so no one could get through. I asked where this ‘open microphone’ was located and he said they had assumed it was within the motorcade because you could hear the motorcycle noise on the Dallas police tape...
I told Penn that if the officer’s motorcycle was in Dealey Plaza then certainly the sound of the gunshots could be heard on the tape too. For some incredible reason no one had ever thought of that fact before. Not once did anyone connected with the Warren Commission, the FBI, CIA or Dallas police ever think to check the tape for gunshots.” 
This early conversation – the springboard for the entire acoustic debate that followed – contains a major falsehood. Penn Jones, Jr., and Gary Mack, now the curator of the Sixth Floor Museum in Dallas, Texas, made the grievous assumption at that time that some of the officers in the motorcade were communicating over Channel One of the Dallas police radio system. In fact, all of the motorcade communications occurred over Channel Two. Consequently, the idea that one of the motorcade motorcyclists might have had an open microphone tuned to Channel One during the shooting had no basis in fact. Many premises – all of them highly improbable – have since been offered by acoustic evidence supporters to explain this initial false premise.
At the end of their meeting, Jones offered Mack a seventh generation copy of the Dallas police recordings to work from, but the recording proved to be too “muddy” to be of any value. 
In January, 1977, Mack received a clearer copy of the police recordings from the grand dame of assassination researchers, Mary Ferrell.  He took the recording to TM Productions and January Sound in Dallas – two audio recording studios – and convinced a few audio technicians to work on the recordings with him. After applying audio filters to remove some of the background noise in the recordings, they found a segment of the tape that contained “little pops and crackles” that “were not repeated anywhere else on the tape.” Mack took the recording home and tried to match the “pops and crackles” to the action seen in the Zapruder film. 
By July of 1977, Mack was convinced he could hear seven distinct shots on the recording.  Despite the fact that a later HSCA investigation would conclude that the “gunshots” were inaudible to the human ear,  Mack wrote in The Continuing Inquiry, a Penn Jones, Jr. published assassination newsletter, that it was “easy” for him and his technicians to hear seven shots and determine their exact sequence on the tape.
“Without any further processing we heard the first shot: a very loud, sharp crack,” Mack explained. After synchronizing the “gunshots” with the Zapruder film, Mack wrote that the seven shots were fired in the following sequence: “...the first shot corresponded to frame 161, indicating a very early diversionary or signaling shot to set up the ensuing crossfire...Then, 2.7 seconds later, shots two and three struck Kennedy almost simultaneously...probably at [Zapruder frames] #208 and #210...Gunshot number four, just 4.9 seconds after the first...had a hollow, metallic sound...[and] more or less corresponds to frame 250 of Zapruder’s film...Frame 289...is precisely where the fifth shot is heard, 7 seconds after the first one...[Shots six and seven strike] almost simultaneously at frames 313 and 315...The entire seven-shot sequence took 8.4 seconds...” 
Playing back the police recording for TV reporters, Mack used a pointed finger to indicate the precise moment of each “gunshot.” He later acknowledged that the segment he thought contained gunshots preceded the impulse sounds identified by HSCA acoustic experts as gunshots by two minutes. 
On September 17, 1977, the newly formed House Select Committee on Assassinations (HSCA) held a two-day conference of Warren Commission critics in Washington, D.C. HSCA Chief Deputy Counsel G. Robert Blakey later wrote that he wondered about the benefits of such a conference, believing that the majority of critics were only interested in “playing on the emotions of a dispirited American public, writing books and articles for profit, with scant regard for the truth, and we were reluctant to dignify that kind of conduct, even by implication.” 
One of those critics attending the conference was Mary Ferrell, the Dallas researcher who was the source of Mack’s copy of the Dallas police recordings. At the end of the first day, Ferrell mentioned Mack’s study and that he had found seven shots on the police tape. By the end of the month, Ferrell turned over her copies of the police recordings to the HSCA for further study. 
In October, 1977, the HSCA contacted the Acoustical Society of America, a professional organization of acoustical engineers and scientists, and asked for recommendations on who was qualified to study the recordings.  Five organizations were recommended. At the top of the list was Bolt, Beranek, and Newman, Inc., (BBN) a Cambridge, Massachusetts, firm that had previously studied the eighteen-minute gap in the Watergate tapes, as well as sound recordings of the 1970 Kent State University shooting of students by the Ohio National Guard. BBN pioneered a technique which allowed them to determine the timing and direction of the gunfire. BBN’s audio work, combined with photographs taken at the scene, allowed prosecutors to establish which guardsmen fired first. 
BBN scientists told the HSCA that if the audio recording contained gunshots and they had a good quality copy to work from, they could determine how many shots had been fired, the timing of the shots, and the source of the gunfire. 
However, on November 17, 1977, after an analysis of Mary Ferrell’s copies of the Dallas police recordings, BBN reported that the copies had “a very scratchy overlay of needle noise, indicating that it was a very poor or multiple-generation dub of [the original] recording.” Consequently, BBN was unable to say for certain whether the recordings did or did not contain the sound of gunshots, as Mack claimed. They would need access to the original Dallas police recordings. 
Four months later, on March 10, 1978, HSCA investigators located the original Dallas police Dictabelt and Audograph recordings, as well as taped copies of the originals, among the possessions of retired Dallas police lieutenant Paul McCaghren. 
The Dallas police radio traffic was routinely recorded onto thin, plastic belts and disks by two separate dual recording units. Channel One, which handled routine radio traffic, was recorded on a Dictaphone Corporation A2TC, Model 5, belt (or loop) recorder purchased by the department in 1957. Channel Two, which handled special event radio traffic like the presidential motorcade, was recorded on a Gray Corporation “Audograph” flat disk recorder which was bought in the early 1950’s. Both dual devices consisted of one unit set to record and a second unit set to take over the recording duties as soon as the first unit was full. 
On May 12, 1978, the HSCA asked BBN to analyze the original Dallas police recordings and determine if they contained evidence of gunshots. Dr. James E. Barger, the lead scientist at BBN was less than hopeful of finding gunshots after a preliminary examination of the Channel One recording thought by Mack to contain gunshots. Barger determined that the recording, to the human ear, contained no audible sounds of gunfire – in contradiction with Mack’s claim that seven shots could be heard. Barger told the HSCA that he was “not hopeful about the prospects of recovering anything from the tape.” However, he agreed to clean up the recording and run a series of tests designed to prove that there were no gunshots on the tape. He reasoned that if preliminary tests showed that no gunshots were on the tape, there would be no need to conduct additional acoustic tests in Dallas, saving the HSCA time and money. The HSCA agreed. 
Two months later, on July 13, 1978, Dr. Barger called the committee and dropped a bombshell – there was evidence of three to five gunshots on the police recordings. The HSCA made arrangements to bring Barger to Washington to brief the committee in executive session. 
For two days, beginning on July 17, 1978, Dr. Barger briefed the HSCA in secret session. He told the committee that what BBN thought might be gunshots were a sequence of “impulse sounds” that appeared on the Channel One recording beginning at about 12:30 p.m. and 47 seconds.  Barger cautioned that while the loudest “impulse sounds” might be gunfire, they could just as easily be motorcycle engine misfires, ignition system noises, intermittent microphone relay sounds, scratches on the surface of the Dictabelt itself, electrical or mechanical distortions due to components in the communication system, or any number of other non-firearm sources.  Barger reported that he had subjected the “impulse sounds” BBN had discovered to “five simple but necessary” test questions – Do the sounds occur at the time of the assassination? Are the sounds unique, occurring only at one time and nowhere else on the tape? Do the time intervals between the sounds match other known evidence (chiefly, the Zapruder film)? Does the “shape” of the sounds, as seen in a waveform, resemble the shapes of known gunfire? Is the volume of the sounds similar to that of known gunfire?  The answer to each of the test questions was, yes. 
Consequently, Barger told the committee, a more sophisticated test was required to determine if any of the “impulse sounds” were actually gunfire. He suggested that BBN be allowed to conduct an acoustic reconstruction in Dealey Plaza – site of the 1963 murder – during which test shots would be fired from locations suggested by eyewitness accounts and compared with the “impulse sounds” on the police recording. If any of these “acoustical fingerprints” matched the impulse sounds on the recording, BBN would be able to determine the timing of the shots, the location of the gunman, and the target for each shot fired. 
On Sunday, August 20, 1978, the HSCA investigative team consisting of four committee staff members, seven acoustic experts, a photographic consultant, and 37 Dallas police officers assembled in Dealey Plaza, along with a crowd of about 200 spectators. 
Since it was impractical to fire test shots from every conceivable firing location, BBN chose two sites that had been featured the most in assassination literature – the Texas School Book Depository and the grassy knoll. Dallas police sharpshooters fired Mannlicher-Carcano rifles  from both locations at four target boxes filled with sandbags at specific locations along Elm Street.  Three of those targets were located at positions that matched that of the presidential limousine at Zapruder frames 160, 200, and 313. A fourth target was placed near the Main Street curb where a bullet was known to have ricocheted. 
To record the test shots, BBN arranged their microphones at eighteen foot intervals along the motorcade route through Dealey Plaza. They used a 14-track recorder to record the gunfire and therefore, were limited to using only twelve microphones at a time (leaving two tracks available for communications); arranged in three separate groups for a total of 36 microphone positions. The combination of microphone positions and multiple test firings provided 432 sound patterns. BBN was confident that if the impulse sounds on the Dallas police recording were indeed gunshots, they would be able to predict the position of the motorcycle with the open microphone to within 18 feet of its actual location. 
Over a five-hour period, fifty-seven test shots were fired in Dealey Plaza. 
On August 30, 1978, Dr. Barger called the HSCA and told them that he had completed his preliminary analysis.  After comparing the 2,592 combinations of echo test patterns obtained in Dallas with the “impulse sounds” on the eight-second sequence of the Dallas police recording, BBN had discovered 15 echo patterns grouped around four periods of time – an indication that four gunshots had been fired in Dallas. The test echo patterns showed that three of the shots were fired from the Texas School Book Depository and one was fired from the grassy knoll. The motorcycle with the open microphone that presumably transmitted the gunshot “sounds” was predicted to be 120 feet behind the presidential limousine. 
On Sunday, September 10, 1978, the day before he was scheduled to testify, Dr. Barger flew to Washington, D.C., and met with HSCA chief counsel G. Robert Blakey, Congressman Floyd J. Fithian of Indiana, and deputy chief counsel Gary Cornwell and explained the process BBN used to reach their conclusion. The men also studied photographs taken at the time of the assassination in an effort to identify the motorcycle with the open microphone, however none of the photos they looked at covered the period of time in question. Blakey promised to “keep looking.” 
The next day, Monday, September 11, 1978, Dr. Barger testified to the committee in public hearings. Statistically, there was 96% chance that the acoustic team had correctly detected two shots, a 75% chance they had correctly identified three shots, and only a 29% chance they had correctly found four gunshots. According to Barger, the probability that a grassy knoll shot had been fired was only 50-50.  Barger reiterated what he had told HSCA members the night before, that the acoustic tests were designed “to see if [the Dallas police tape] was statistically likely to have contained the sounds of gunfire,”  and that the results he obtained were “a potential corroborating force toward other evidence.”  In short, it was up to the HSCA to find additional evidence that either confirmed or refuted the acoustic tests.
As to the location of the motorcycle with the open microphone, Barger testified that at the time of the first shot, his statistical analysis predicted that the open microphone was on Houston Street about 120 feet, plus or minus 9 feet, behind the president’s limousine.  When Barger was asked by HSCA chairman Louis B. Stokes whether he had studied “any available photographs or films in order to try and make a more accurate placement of the motorcycle,” Barger said that photographs taken of that area at the time of the shooting didn’t reveal the presence of any motorcycles. “We have seen some photographs taken less than 1 minute before the shooting,” Barger said, “and there are motorcycles back there, but there is so much time elapsed between those pictures and the time of the shooting, it wouldn’t help us [place the motorcycle with any more precision].” 
HSCA chief counsel G. Robert Blakey later wrote, “Barger turned out not to be very persuasive. All of the virtues that made him a fine scientist worked against him as a witness. He was too precise. His answers were too qualified. The Committee, the audience, and the press wanted clear-cut answers. When Barger told them the truth, the impact of his testimony was lost.” 
That evening, the HSCA staff decided to ask two Queens College acousticians they had consulted earlier – Mark Weiss and Ernest Aschkenasy – to see if they could refine BBN’s work and come up with better percentages. At first, Weiss and Aschkenasy weren’t optimistic, but after consulting with Dr. Barger, they came up with a mathematical extension of BBN’s efforts that they thought could reduce the element of chance. 
On October 24, 1978, the HSCA authorized Weiss and Aschkenasy to study the impulse sounds associated with the shot fired from the grassy knoll. The HSCA reasoned that since this was the only impulse sound that indicated a conspiracy (all other impulse sounds matched test shots fired from the Texas School Book Depository), they could use their limited time more effectively by concentrating on this one impulse sound. 
On December 11, 1978, Weiss and Aschkenasy, along with Dr. Barger, met with HSCA members in executive session and presented their united findings – they could show with refined mathematical techniques that the certainty of a grassy knoll shot was now 95 percent.  In addition, HSCA photographic consultant Robert Groden had uncovered several amateur film clips that showed motorcycle officer H.B. McLain traveling on Main Street and turning onto Houston Street at about the right time. “McLain was our man,” Blakely later wrote. 
On December 18, 1978, Dr. Barger, Weiss and Aschkenasy, again met with HSCA members to answer questions. Mark Weiss explained that his refined mathematical technique assumed as given the speed and location of the suspect motorcycle on Elm Street. Representative Harold Sawyer asked, “If that location is “significantly wrong, then all that proceeds from that is subject to the same fallacy. Is that correct?” Weiss replied, “Well, if the location of the motorcycle is not where I found it to be, you will not get a set of predicted echo occurrences which agree in any way with what is observed in the Dallas police tape recording.” 
On December 26, 1978, HSCA Deputy Chief Counsel Gary Cornwell asked former committee staff consultant Richard E. Sprague,  a pioneer in the field of electronic computers best known for his intimate knowledge of the photographic evidence in the Kennedy assassination, to help identify the motorcycle with the open microphone. Sprague subsequently examined numerous films and photographs, including those taken by James Altgens, Robert Hughes, John Martin, Orville Nix, Malcolm Couch, Dave Wiegman, Mark Bell, and Marie Muchmore, and found no motorcycle in the location indicated by the acoustic panel. Sprague called Cornwell the next day and told him, “Gary, I’ve got bad news for you.” Sprague explained that three films alone prove that no motorcycle was near the area predicted by the acoustic evidence. According to Sprague, the Hughes film proved no motorcycle was any closer than 220 to 250 feet from the limousine at the time of the first shot. The Couch and Wiegman films proved that no motorcycle was 120-140 feet behind the limousine at the time of the last shot. Slides which Sprague made proving his findings were picked up later that day for viewing by the HSCA staff in Washington. The next day, a staff member told Sprague his slides didn’t “prove anything one way or another.” 
On December 29, 1978, just 5 days before the HSCA’s investigation was scheduled to expire, the committee met for one final day of televised public hearings. In dramatic fashion, Weiss and Aschkenasy faced the cameras and testified, “It is our conclusion that as a result of very careful analysis, it appears that with a probability of 95 percent or better, there was indeed a shot fired from the grassy knoll.” 
After the acoustic scientists explained their process to the committee, HSCA chief counsel Blakey called Dallas police officer H.B. McLain to testify. McLain, the HSCA believed, was the one responsible for the open microphone. 
McLain identified himself in a series of frames culled from two amateur films. One sequence, from the Dallas Cinema Associates (DCA) film “President Kennedy’s Final Hour,” showed McLain traveling on Main Street a few blocks before reaching Dealey Plaza.  The second sequence, from a film by Robert Hughes, showed McLain turning from Main onto Houston Street, one block behind the president’s limousine, which had just turned onto Elm Street.  Since the acoustic evidence predicted the motorcycle with the open microphone was about 120 feet behind the president’s limousine at the time of the first shot,  and because McLain was the only motorcycle officer in the area, the HSCA concluded that McLain “would have been in the approximate position of the transmitting microphone, as indicated by the acoustical analysis.” 
Dr. James Barger then appeared again before the committee to show his support for Weiss and Aschkenasy’s work. Asked about the lack of photographs or films that verified the acoustic panel’s conclusions, Barger acknowledged that the “major shortcoming” of their acoustic work “was that there was no evidence that there was a motor vehicle where we had found it to be.” Barger later conceded that the lack of photographic verification of the acoustic evidence was “a very obvious place from which to attack the analysis.” 
Even Blakey acknowledged during his opening narrative remarks that, “If it could be proved that no motorcycle was in the predicted location at the time of the shots, then serious doubt would be raised about the reliability of the acoustics project.”  What Blakey should have said, of course, was that the acoustics evidence would be destroyed by such proof.
On Sunday, December 31, 1978, HSCA chairman Louis B. Stokes announced the committee’s judgment in a 17-page report to the Clerk of the House, Edmund L. Henshaw. After six hours of heated debate behind closed doors, the HSCA concluded that “scientific acoustical evidence established a high probability that two gunmen fired at President John F. Kennedy” and that the President was “probably assassinated as a result of a conspiracy. The Committee is unable to identify the other gunman or the extent of the conspiracy.” 
Three members of the twelve member HSCA panel – representatives Harold S. Sawyer (R-MI), Robert W. Edgar (D-PA), and Samuel L. Devine (R-OH) – vigorously dissented from the committee’s four shot conclusion.  Representative Harold Sawyer believed that the photographic evidence of a motorcycle needed to validate the acoustic evidence was only suggestive, not proof that one actually existed at the predicted times and locations. Sawyer told the press, “I am not myself persuaded by the committee’s acoustical findings...That the motorcycle was there does not appear – from my reading of the evidence in the committee’s report – to have been certainly established.”  Representative Robert Edgar said, “We found no evidence to suggest a conspiracy. We found no gunmen or evidence of a gunman. We found no gun, no shells, no impact of shots from the grassy knoll. We found no [frontal] entry wounds...We found no bullets or fragments of bullets that did not belong to the Oswald weapon. And we found little, if any, evidence of partnership with Lee Harvey Oswald. Few credible ear witness accounts back up the marginal findings of our acoustics experts.” 
Gary Mack, who had started the ball rolling on the acoustic evidence so heavily relied upon by the HSCA, told a radio industry trade newspaper, “I take great personal pride in the part that I was able to play in all this. As it turns out, I stumbled upon the first hard evidence of any conspiracy, and for that reason I think we are getting closer to the full story.” 
On January 4, 1979, just four days after the Stokes statement was released, former Dallas police officer H.B. McLain met with former Dallas police radio dispatch supervisor James C. Bowles, who played the 1963 Dallas police radio recordings for McLain. It was the first time McLain had heard the recordings. After listening to both recorded channels, McLain declared, “Man, there’s no way that could have been my mike stuck open!” McLain recalled the conversations recorded on Channel Two (the motorcade communications channel) but had no recollection of the Channel One conversations (those recorded in and around the stuck microphone segments). McLain also pointed out that the sound of the motorcycle with the open microphone indicated that it was traveling way too fast to be part of the motorcade; that the motorcycle with the open microphone never turned on its siren (something McLain insisted he did); and that the sirens heard on the recording appear to be passing a stationary microphone, not one catching up with the motorcade two minutes after the shooting, as the HSCA claimed. 
Concluding his own investigation into the sounds heard on the Dallas police recordings in 1979, James C. Bowles wrote a 214-page report on the acoustic evidence and the HSCA’s handling of it. In it, he blasted the HSCA’s contention that a voice-grade recording system was capable of transmitting and recording non-audible N-waves created by gunshots; pointed out the absence of known sounds related to the motorcade on the recordings; and offered strong evidence that the motorcycle with the open microphone was at or near the Trade Mart, and not in the motorcade. 
On January 30, 1979, ten of the nation’s leading conspiracy theorists met in New York at a JFK assassination symposium sponsored by Gallery magazine. During that conference, three of the attendees – Gary Mack, Jack White, and Robert Groden – announced that they had found the photographic verification of the acoustic evidence that the HSCA had been looking for.  The evidence was an amateur film made by Elsie Dorman which, according to Mack, White, and Groden, showed motorcyclist McLain at the Elm and Houston corner at the time of the first shot; exactly as the HSCA’s acoustic panel had predicted.  Groden subsequently submitted frames from the Dorman film to the HSCA;  and while the HSCA emphasized that they did not rely upon Groden’s new photographic evidence to draw their final conclusions, their report does say that the Dorman frames “supported the committee’s conclusion.” 
On March 3, 1979, former HSCA photographic consultant Richard E. Sprague wrote a letter to representative Harold Sawyer condemning Groden’s so-called photographic verification of the acoustic evidence. Sprague wrote that the “motorcycle location [the acoustic experts] came up with is provably wrong...Elsie Dorman’s movie taken from the fourth floor of the [Depository], proves [along with the Wiegman and Couch film] that there was no motorcycle at all, where Weiss, Barger and Aschkenasy say it had to be...” 
Sprague also condemned the HSCA’s use of the Robert Hughes film as evidence that McLain was in approximately the correct position to transmit the sounds of gunfire. Sprague wrote that McLain couldn’t possibly have covered the 170-foot distance between his last known position shown in the Hughes film and the position dictated by the acoustic evidence in the 3.5 seconds that Sprague estimated McLain would have had available to him. 
On January 7, 1980, Sprague wrote to U.S. Attorney General Benjamin R. Civiletti asking for an opportunity to meet with him and show him photographic evidence that disproved the HSCA’s acoustic analysis. Sprague explained that “a few days before the committee’s final hearings on the acoustical evidence, which eventually led them to a conclusion of conspiracy, I called to their attention some important photographic evidence. This evidence proves that the acoustical analysis by the committee’s outside consultants at Bolt, Beranek and Newman; and by Professors Aschkenasy and Weiss, is faulty. I called this faulty analysis to the attention of the outside consultants, the committee’s staff, and the committee’s members, both before the last hearings and during the hearings, as well as during the period when the staff was working on the final report. All of them ignored this evidence and you will find no mention of it in the final report or in Volume VI of the appendix to the report covering the photographic evidence.” 
On March 11, 1980, Sprague met with two Justice Department attorneys and four members of the FBI’s Technical Services Division. Sprague presented his photographic evidence. Included were the photographs and films of James Altgens, Dave Wiegman, and Malcolm Couch, which demonstrated that McLain was “more than 250 feet behind JFK when the shots were fired.”  By the end of the meeting, the FBI and Justice Department officials were “convinced” that McLain was nowhere near the location necessary to validate the acoustic evidence. 
In early April, 1980, Gary Mack, who instigated the HSCA’s acoustic study, scolded Sprague, calling his efforts to undermine the acoustic evidence “rather foolish;” adding, “The real net result, Dick, is that you’ve made some serious errors that reflect strongly on your credibility.” Mack countered Sprague’s arguments by claiming that McLain had six to seven seconds to cover the 170-foot distance on Houston Street, not the 3.5 seconds estimated by Sprague; that the Dorman film showed McLain arriving at the time of the second shot,  not well after the last as claimed by Sprague; and that a new study of the Zapruder film showed McLain at the corner of Elm and Houston at Zapruder frame 179 (i.e., the period between the first and second shots).  All three of Mack’s assertions later proved false.
In the fall of 1980, at the request of the U.S. Department of Justice, the National Research Council established the Committee on Ballistic Acoustics (CBA) to review the HSCA’s acoustic findings and methodology. The CBA, led by Harvard University professor Norman F. Ramsey, included eleven other top scientists: Luis W. Alvarez of the Lawrence Berkeley Laboratory at the University of California; Herman Chernoff, Massachusetts Institute of Technology; Robert H. Dicke, Princeton University; Jerome I. Elkind, Xerox Palo Alto Research Center; John C. Feggeler, Bell Telephone Laboratories; Richard L. Garwin, IBM Corporation; Paul Horowitz, Harvard University; Alfred Johnson, National Laboratory Center; Robert A. Phinney, Princeton University; Charles Rader, Massachusetts Institute of Technology; and F. William Sarles, Trisolar Corporation. 
On March 4, 1981, on the heels of an FBI report critical of the HSCA acoustic panel’s conclusions, Dr. James Barger wrote a letter to Louis Stokes, former chairman of the HSCA, stating, “The most meaningful and the most direct method of verifying whether we have proved that the impulse patterns on the DPD recording are caused by gunfire in Dealey Plaza is to examine independent evidence about the motorcycle trajectory and about the shot timing sequence that our analysis revealed…The HSCA did find that both the motorcycle trajectory and the shot sequence we found were consistent with independent photographic evidence.”  Later in the letter, Barger adds, “…photographic evidence was found by the HSCA that showed a motorcycle on the [trajectory] that we had
In fact, the HSCA was never able to confirm McLain’s presence at the locations predicted by Barger’s analysis, nor did Barger have any first-hand knowledge about such photographic validation. 
On January 31, 1982, the CBA members met for the first time and compared notes from the independent studies they had been conducting since the committee’s inception. By the end of the day, the group was convinced that the HSCA acoustic panel’s methods were so faulty that it rendered their acoustic evidence of a conspiracy useless. 
On March 2, 1982, Gary Mack wrote a letter to CBA physicist Norman Ramsey explaining that he was aware of new photographic evidence that showed H.B. McLain’s motorcycle at the time and location predicted by the HSCA acoustic analysis, thereby validating the acoustic evidence. This time the “evidence” turned out to be Zapruder frame Z183 which reportedly showed McLain’s motorcycle between shot positions 1 and 2. Mack wrote, “HSCA Assistant Staff Counsel Gary Cornwell spotted [McLain] while reviewing the film with HSCA Photo Consultant Robert Groden in Fall, 1978. Groden concurred with Cornwell’s observation, and is now preparing a new print for study.”  Neither Groden nor Cornwell ever mentioned their finding publicly. Cornwell later denied the observation.  The object thought to be McLain is actually a 1963 Mercury Comet convertible carrying Dallas Mayor Earle Cabell and his party.
On May 14, 1982, the CBA released their final report which concluded, based partially on the work of Ohio percussionist Stephan N. Barber, that the HSCA’s acoustic work was seriously flawed and that “the previously analyzed sounds were recorded about one minute after the assassination and, therefore, too late to be attributed to assassination shots.” 
In a February 18, 1983, letter to G. Robert Blakey, Dr. James Barger agreed that the NAS-CBA report seemed to show “that the sounds that we connected with gunfire were made about a minute after the assassination shots were fired.” However, Barger noted that the recording used by the CBA contained “some enigmatic features” that raise “doubt about the time synchronization of events on that recording.” Therefore, Barger concluded, there is some doubt as to whether the NAS-CBA had proven that the acoustic evidence was invalid. Barger suggested that further analysis was needed and suggested a number of studies, including, a “photographic examination of McLain’s trajectory.” Barger wrote, “It is important to compare our best photographic estimates of McLain’s trajectory with our best acoustical estimates…We understand that further work has been done here,  but not having seen it, we don’t know if an adequate analysis has been done.” 
In April, 1988, Richard E. Sprague’s photographic evidence that motorcycle officer H.B. McLain was not where acoustic experts had predicted was resurrected in an article published in Bob Cutler’s Grassy Knoll Gazette. Researcher Todd W. Vaughan, who had been corresponding with Sprague, noted that the Robert Hughes film and the Zapruder film both showed the fifth car in the motorcade, the Vice-Presidential Secret Service Follow-Up car, making its turn from Houston onto Elm Street. Using the Secret Service car as a synchronization point, Vaughan concluded, after “eyeballing” the two films, that at the time of the first shot McLain was 230 feet from the position dictated by the HSCA’s acoustic evidence and therefore couldn’t possibly have been in a position to transmit the sound of gunshots. 
In a July, 1990, article published in Jerry Rose’s The Third Decade, research Sim Heninger made a similar observation by also “eyeballing” the Hughes and Zapruder films. Heninger wrote that the Hughes film “actually proves that McLain was barely past the intersection of Houston and Main Streets when the shooting began.” Heninger reached his conclusion after observing that the fifth car in the motorcade, the Vice-Presidential Secret Service Follow-Up car, could be seen turning the corner from Houston onto Elm Street in both films, and consequently the synchronization of both films seemed to show McLain “300 feet from where the open microphone had to have been.” Heninger also pointed out that the Dorman film showed McLain arriving at the Elm and Houston corner “after the head shot,” not at the time of the first shot as Robert Groden had told the HSCA. 
On November 20, 1997, assassination researcher Greg Jaynes presented the same hypothesis as Vaughan and Heninger to a gathering of researchers sponsored by JFK/Lancer. Jaynes told the attendees that the Hughes film segment showing McLain at the corner of Main and Houston synchronized to the Zapruder film “around frame 160 plus,” and that McLain couldn’t have been in a position to transmit the “impulse sounds” thought to be gunshots by the HSCA acoustic experts. Jaynes also noted that the Dorman film showed McLain arriving at the location designated by the acoustic experts as the first and second shot positions well after the shooting had ended. Jaynes’ presentation, which also relied on “eyeballing” the Zapruder, Hughes and Dorman films, was later published on the Internet. Similar observations have appeared on the Internet in more recent years. However, none of these Internet reports have offered a comprehensive scientific analysis or a definitive conclusion. 
In a 2001 email message, Barger wrote that he had never personally seen any films relating to the acoustics evidence, adding, “I limited my work for HSCA to analysis of the police radio channel recordings. At the time I presented my findings, several Congressmen asked me how they were to interpret my results – since I presented them in probabilistic form. I told them that it was up to them to look for corroborating or impeaching independent (of my analysis) evidence. I mentioned several kinds of independent evidence that would corroborate my findings. One of these was, of course, whether they could find a vehicle or person with a police radio near where I had found it. I remember Bob Blakey told me that they had found such evidence, but I don’t remember the name of the person whose film was thought to contain this evidence.  I gather from the [email] traffic I’ve seen…that this evidence is in dispute - at least between some of you. Well, it’s an important question, because if it can be shown that there was no vehicle or person with a police radio near the trajectory where I found it to be, then, that is impeaching evidence.” 
In March, 2001, Science & Justice, a quarterly publication of Britain’s Forensic Science Society, published a paper by Donald B. Thomas, an entomologist and part-time assassination researcher working for the U.S. Department of Agriculture’s Subtropical Agricultural Research Laboratory in Weslaco, Texas. Thomas became convinced of a conspiracy in the Kennedy assassination after viewing Oliver Stone’s 1991 motion picture, JFK. In his Science & Justice published paper, Thomas claimed that the CBA report was flawed and that a statistical review of the HSCA acoustic work confirmed their findings and elevated the probability of a grassy knoll shot from 95 to 96%. Thomas also suggested that five shots, not four as the HSCA had concluded, had been fired in Dealey
Former HSCA chief counsel G. Robert Blakey, eager to embrace any study critical of the CBA’s devastating critique of his committee’s findings, called Thomas’ study “an honest, careful, scientific examination of everything we did, with all the appropriate statistical checks.” 
However, eight months after his findings made worldwide news, Thomas acknowledged to a small group of assassination researchers at a conspiracy conference that his objection to part of the CBA’s hypothesis were “largely blown away” after he examined a statistical analysis of a more complete version of the Dallas police recording which he had recently gained access to – the same recording used by the CBA 19 years earlier. Thomas emphasized, however, that his acknowledgment shouldn’t be construed to mean that he believed that the CBA hypothesis was correct, merely that the CBA hypothesis was “now plausible.”  Thomas went on to offer a number of arguments which buttressed his original Science & Justice paper which concluded that five shots were fired in Dealey Plaza and that the fourth shot, fired from the grassy knoll, was the fatal head shot.
In 2003, Medstar Television and Court-TV commissioned Robert Berkovitz of Sensimetrics Corporation to re-examine the acoustic evidence using the latest computer technology for a forthcoming 40th anniversary television special. Berkovitz concluded that the CBA was correct in their conclusion after all; that the impulse sounds deemed to be gunshots by the HSCA acoustic teams were actually recorded about one minute after the assassination, and therefore, too late to be assassination
Berkovitz’ 2003 work for Court TV was immediately challenged by Donald Thomas. Thomas charged in an Internet-posted rebuttal that Berkovitz’ “lack of familiarity with the evidence in the case, and perhaps a lack of time, resulted in a lackadaisical study.” 
On November 20, 2003, ABC television broadcast Peter Jennings Reporting: The Kennedy Assassination – Beyond Conspiracy, a two hour 40th anniversary look at the crime of the century. The ABC News special featured sequences from Dale K. Myers’ computer reconstruction of the shooting as well as the conclusions he had reached after conducting an epipolar geometric analysis of amateur films related to the acoustic evidence. Myers concluded that H.B. McLain’s motorcycle was 174 feet from the location predicted by the HSCA’ acoustic experts at the time of the first shot and that the acoustic evidence of a conspiracy was invalid.  His photographic work on the acoustics issue was ignored by conspiracy proponents and arguments for and against the validity of the acoustic evidence reverted to “acoustic” questions.
In early 2006, Science & Justice published a research paper by physicists R. Linsker, Richard L. Garwin, Herman Chernoff, Paul Horowitz, and Norman F. Ramsey; three of whom were distinguished members of the 1982 Committee on Ballistic Acoustics (CBA). The scientists rebutted entomologist Donald Thomas’ original 2001 thesis as well as his subsequent critiques. The physicists wrote that their paper “identifies serious errors in the Thomas paper and corrects errors in the [CBA] report. We affirm the earlier conclusion of the [CBA] report that the alleged ‘shot’ sounds were recorded approximately one minute after the assassination.” 
In late 2006, Science & Justice published a letter from Donald Thomas seeking to rebut the critique of the eminent physicists. Thomas claimed that the conclusions of Linsker et al. relied “more on assumptions than on data.” 
However, in a scathing response to Thomas, published in Science & Justice, physicists R. Linsker, Richard L. Garwin, Herman Chernoff, and Norman F. Ramsey demonstrated that it was Thomas’ argument “that relies more on assumptions than on data.” The scientists showed that Thomas continues to draw conclusions based on unreliable dispatcher annotations; misunderstands and misrepresents the physicists’ analysis; and wrongly claims that their analysis supports his conclusions. 
Despite the tremendous weight of credible voices who have denounced the HSCA’s acoustic work acoustically over the years, the thin voices of a few skeptics, like Thomas, continue to find an audience.
The innumerable errors in Thomas’s work are abundantly evident to the scientific community, but laypersons can’t seem to take the time to wade through them. There is, however, an easily accessible method of resolving the debate over the validity of the acoustic evidence photographically.
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