In 1978 the House Select Committee on Assassinations was presented with acoustical evidence that multiple shooters had been involved in the murder of President John F. Kennedy. During the hearing, staff members played a tape recording for the Committee with the explanation that they were about to hear a rifle shot fired from the Grassy Knoll. After listening to this tape the ranking Republican member of the Committee, Representative Samuel Devine of Ohio, rose in the chamber to declare that he had a great deal of experience with firearms and familiarity with rifle fire. He knew a gunshot when he heard one, he said, and the sound alleged to be from the Grassy Knoll could be many things, but it was clearly not a rifle shot. The staff then explained to Mr. Devine that the tape recording was of a test shot fired from the Grassy Knoll that summer; not the Dallas Police tape from 1963. The incident suggests two things. First, that one cannot determine that a recorded sound is or is not gunfire merely by listening with the naked ear. Secondly, it suggests that Congressman Devine may not have been completely open-minded to the concept under investigation by his Committee.

Over the last year I have discovered that there are others who are less than receptive to this evidence. While experiencing my fifteen minutes back in March, appearing on television and radio, the producer for ABC's Nightline program asked me if I realized that the article I had published (in the British forensic journal Science & Justice) had made a lot of people very angry. I said that, yes, I understood that. He then remarked that, on the other hand, I had undoubtedly made a lot of conspiracy buffs very happy. "Well, no, not really," I said. The acoustic evidence does contradict the official version of events which holds that there was no more and no less than exactly three shots. But, I explained, most conspiracy buffs are convinced that JFK received at the very least, a frontal shot through the throat, and another through the head as well. The acoustical evidence indicates only one shot from the front. Moreover, when one synchronizes the acoustical evidence with the filmed evidence, the shot from the front aligns with the head shot. The lack of evidence for a frontal shot for the throat wound tends to support the single bullet theory, and the single bullet theory is anathema to most conspiracy buffs.

The producer told me that in journalism, when those on opposite sides of an issue are both unhappy with the reporting, they like to think that they are probably doing something right. I am not sure that this is a perfect analogy, but the point is that, as I stand before you today, I am perfectly well aware that many if not most of you are not yet convinced by this evidence. And I hasten to add that I am not going to try to convince you. I have a good friend who teaches Biology at a college in Georgia, a course which includes instruction in Evolution. Naturally, his students include many who are devoutly religious. He tells them, what I wish to tell you now. I don't care what you believe, but, I do care that you know the facts.

When I first wrote my article on the acoustics, I submitted it to the Journal of Forensic Science here in the United States for publication. The editor kicked it back, stating that it was their editorial policy not to publish articles on the Kennedy assassination. He defended this policy on the grounds that no amount of reanalysis was going to change anyone's mind. As one who routinely reviews scientific articles for publication, I must say that this seemed like an odd position for a scientist to take. And I reiterate that I am not trying to change anyone's mind. My mission is to present the facts and let people make up their own mind. Having said that, I am going to avoid as much as possible making an overly technical presentation of the acoustical evidence today. The reports of the acoustics studies are available in the HSCA proceedings if anyone needs those details. Rather, in my talk today I am going to address the criticisms of the acoustical evidence that have been brought to my attention, and to show how the acoustical evidence meshes with the other crime scene evidence, particularly the Zapruder film.

One of the criticisms that I have been personally subjected to was brought up, among other places, on the Fox Morning News program. The host of that show said, "You're just an entomologist, why should anyone believe you?" Now you should understand that these shows are rehearsed. The producer of the program likes to know ahead of time what the guest is going to say, in part so they have interesting discussion, and in part so the host doesn't look stupid. So I knew the question was going to be asked. I was tempted to say that, "No, I am not an acoustical expert, but I did stay in a Holiday Inn last night." Instead I pointed out that even an entomologist knows that a scientific hypothesis stands or falls on the evidence behind it and not on the status of the person who makes it. I might also have pointed out that if expertise were the issue -- then I win.

When the House Select Committee on Assassinations was first confronted with this evidence, they asked the Acoustical Society of America for a short list of the top acoustics laboratories in this country. At the top of the list was the expert consulting firm of Bolt, Baranek & Newman (BBN)of Cambridge, Massachusetts. They had done the Watergate tapes for the Ervin Committee and the acoustics study of the Kent State shooting for the Department of Justice. These experts determined that the assassination gunfire was on the Dallas police tapes and they were the experts who found the "fingerprint" of a gunshot from the Grassy Knoll.

Because that finding was politically incorrect, and because there was an element of uncertainty with regard to the alleged grassy knoll shot, a second expert opinion was sought. Back to the short list, the next laboratory was the Computer Science Department of Queens College, New York, where Professor Mark Weiss and his assistant Arnold Aschkenasy wrote computer programs with sonar applications for the military. They had also published on methods for detecting and separating real sounds from noisy backgrounds. Using the principles of sonar analysis (echo location) they eliminated the cause of the uncertainty and concurred that there was scientific evidence of a shot from the Grassy Knoll on the police tapes.

So, if expertise is what one requires, the top acoustic experts agree that there was scientifically valid evidence for a shot from the Grassy Knoll. Moreover, there has never been a direct challenge to the acoustical evidence, or its analysis, or the methods which were used to determine that shots were present on the police tapes.

During the tenure of the House Select Committee on Assassinations, Acoustical experts determined that the sounds of the Kennedy assassination had been captured by a Dallas Police radio microphone and recorded by their communications recording system. It was further determined that among the sounds determined to be gunshots was one which had been fired from the Grassy Knoll. Because of the considerable historical significance of this evidence another opinion was sought and the findings of the first laboratory were confirmed by a second. These findings led to the official conclusion of the Assassinations Committee that there probably was a conspiracy behind the death of President Kennedy. A formal request was made to the Department of Justice to reopen the case for the purpose of identifying the perpetrators. The Justice Department chose instead to commission yet further study of the acoustical evidence. This third study, conducted by a panel organized by the National Research Council found that the HSCA conclusion was invalid on the grounds that the sounds alleged to be the assassination gunfire had been deposited on the Dallas Police recordings at a point in time after the assassination was over. The purpose of my presentation today is to address this issue and to explain how one might arrive at a different conclusion.tapes.

In 1977, Mary Ferrell, a Dallas legal secretary and tireless JFK researcher, told the newly created House Select Committee on Assassinations (HSCA) that she'd heard an audiotape of Dallas police radio traffic around the time Kennedy died. That led the panel to retrieve the Dictabelts in May 1978. By then, the science of acoustic analysis had come a long way. The HSCA's general counsel, ex-federal prosecutor G. Robert Blakey, chose James Barger, a prominent audio scientist, to assess the recordings' value as evidence.

Barger decided to compare the sound impulses on the recordings with the sound of real gunfire. In August 1978, he led a team to Dallas for a series of elaborate ballistics tests. Setting up 36 microphones along the Dealey Plaza motorcade route, he recorded shots fired from the sixth-floor book depository window where Oswald was said to have fired, and from the grassy knoll. Barger compared the resulting sound patterns with the impulses on the Dictabelt. His findings contrasted with those of the Warren Commission, which ruled that Oswald fired three shots at Kennedy's limousine.

Barger identified at least four sound-wave patterns that he said closely resembled the muzzle blasts of gunshots in his test firing. Three of them closely resembled shots fired from the sixth-floor window. One resembled a shot from the grassy knoll, he said. Two other acoustic experts retained by the HSCA supported Barger's conclusion. The acoustic evidence became the keystone of the House panel's finding in January 1979 that Kennedy had "probably" been killed by conspirators who, besides Oswald, couldn't be identified.

Other experts disputed the findings. In 1980, the Justice Department turned to the National Research Council, a government think tank. In May 1982, a 12-scientist NRC panel unanimously ruled that Barger's supposed gunshots were something else and "came too late to be attributed to assassination shots." (A Court TV analysis last year found essentially the same thing.)

Dictabelt No. 10 then went back to a file cabinet at the Justice Department. It was subsequently transferred to the National Archives. Then, in early 2001, Donald Thomas, a government scientist interested in the Kennedy assassination, published in a British forensics journal an article based on a mathematical review of all the acoustic evidence. Thomas's conclusion: Five shots had been fired at Kennedy's motorcade from two different directions.

REX: Alright, this is Rex Bradford; we're here with Don Thomas, who published an essay in "Science and Justice" in 2001, which revived the debate on the acoustics evidence in the Kennedy assassination. Hi, Don.

DON: Hello, Rex.

REX: Um, I'd like to start just by asking how you came to write that article and just give us a brief introduction as to what it's all about.

DON: Well, I was interested in all aspects of the Kennedy assassination, most particularly in the forensic evidence, because I'm a scientist by profession and therefore tend to put more faith in hard evidence and the scientific analysis of evidence. One of the aspects of the evidence that stood out, I suppose, was the acoustical evidence. It had been criticized strongly, and actually I had written up a huge manuscript dealing with all the forensic evidence, searched around for a publisher - no one was interested - and then I backed off, and said "Well, I guess the way to approach this is to go the scientific journals," and so happens I started with the acoustics evidence, and as far as - to give you, I guess, a basic outline of what the forensic evidence shows, I know there's a little bit of confusion because the House Select Committee on Assassinations - I should say that I'm not an acoustics expert myself - uh, the House Select Committee on Assassinations hired acoustical experts to analyze a recording that was made by the Dallas Police at the time of the assassination.

It was actually - to back off - it was Mary Ferrell - who was the one actually brought attention to the House Select Committee on Assassinations that this recording existed, and that there was a possibility that the sounds of gunfire was on the recording. And, as it turns out, the acoustical experts, both Bolt Beranek and Newman, same folks who had done the Watergate tapes, perhaps more importantly they had done the Kent State shooting tapes, analyzed the recording and found evidence for gunfire on the recording.

REX: Right, so they ended up coming up with shots on the tape, including a shot from the "Grassy Knoll," which was one of the factors which led the HSCA to their probable conspiracy conclusion, right?

DON: (coughs) Excuse me, right.

REX: So, I want to fast forward back to your work, I mean, that HSCA acoustics evidence was reportedly debunked, first by a FBI report, then by the Ramsey Panel appointed by the National Academy of Sciences in the early eighties. It sat there for quite a while. I'm curious, when did you first start picking up on that thread?

DON: I guess it was really, it was right after the movie JFK came out - Oliver Stone. Up 'til that time, I had no interest in the Kennedy assassination, and actually before seeing the movie, it was really an article by Newsweek that attacked the movie. I was really struck by that, because here was a six-page cover story article which was entitled "Twisted History," claiming that Oliver Stone's movie was - implying at least - that it was a pack of lies, and yet in the entire article, they did not cite a single example of a falsehood or an untruth - an error - and that struck me as odd. So I started reading about the assassination, and of course, I got especially interested in the scientific evidence, and that led into the - eventually - working on the acoustics evidence.

REX: And your expertise is statistics, primarily, although it sounds like you've branched out into a more full analysis than just running the numbers on that, right?

DON: Yeah, the statistical analysis was one part of it that it was - the House Select Committee - I'm sorry, the National Research Council - had been asked to uh - by the FBI - to review - by the Justice Department - to review the work that was done by the acoustical experts. If I could elaborate on that slightly, you mentioned the FBI study and the NRC study, actually came to kind of different conclusions.

I should point out that the work that was originally done by BBN, when they concluded that they had found the gunshots, the House Select Committee itself asked for a second opinion, so they had the Computer Science Department at Queens College - folks that are sonar experts - to review the evidence. They confirmed and actually extended the study to show that there was a gunshot from the Grassy Knoll among the shots that were identified by BBN. Now, the explanation for what is happening here is - the approach to trying to debunk that evidence by - first by the FBI - well, pretty much simultaneously, the FBI and NRC panel kind of worked together on this, and yet came to different conclusions. The NRC panel, their primary argument was that these sounds are not synchronous with the time of the assassination. That is, the sounds acoustically identified as gunfire, they claim were recorded about sixty seconds after the assassination.

The FBI report, on the other hand, its approach was that, "yes, these might be the sounds of gunfire that killed President Kennedy, but mixed among these might be a vehicle backfire, or big firecracker, or some other sound mixed in there." That would explain the Grassy Knoll shot- supposed Grassy Knoll shot. So, the debunking by the two different groups were actually quite different.

REX: Sure. OK, I'd like to come back a little later in our talk to some of those questions, because you have detractors in 2006, and that it's still controversial. But first, I'd like to say that, let's assume in fact that this is true - that your analysis based on the HSCA's earlier work of the gunfire occurred as it did, and let's just explore what that really means. I'd like to go through the shot sequence in fact, and also talk about some of the corroborating evidence, things like the jiggle analysis.

Why don't we start there? I mean, the acoustics evidence itself doesn't stand alone, and it seems like it's corroborated by analysis of the Zapruder film. Can you elaborate on that?

DON: Sure, that's exactly right. It should be emphasized that it's not just the acoustical matching. The fact that they went to Dealey Plaza, fired test shots, and that those test shots were shown to match to the sounds that are on the police tape. It was the fact that they actually matched in order - there was order in the data. And that's important, because that serves as a test that we can go back and use filmed evidence to see if that sequence is actually something that is sensible. Now that -

REX: I'm sorry, by order in the data, you mean where the open microphone that was apparently on a police motorcycle - where that was located from one sequence to the next?

DON: Right. Exactly. On the recording itself, what you hear on the police recording - for about five and a half minutes - you can hear the sound of a motorcycle motor. So what had happened, on the police channel - which was used for normal communications, for five and a half minutes you're essentially jammed, by - somewhere in Dallas - a microphone on a motorcycle cop's radio has jammed open, so you hear the sound of a motorcycle motor.

You also hear - on the recording - you also hear sirens. And this is the clue that led people to think that this was the assassination - that this was the motorcycle that was with the motorcade at the time of the assassination because the one event that was happening, the one emergency that would require sirens was the fact that the President's motorcade was on its way to Parkland Hospital immediately after the assassination.

Now, as far as the order of the data is concerned, when the acoustical experts did their matching procedure, it would be important to know exactly where the motorcycle was relative to the buildings because the patterns - the sound patterns - that are on the tape are presumed to be echoes - echoes off of the buildings in Dealey Plaza. And so the position of the shooter, the position of the microphone are important in determining whether or not you really have a match.

Now, since the acoustical experts didn't know where the motorcycle was, but they did know that the motorcade was first on Houston Street and then on Elm Street, what they did was they put out an array of 36 microphones in a row - in a line - on Houston Street and then on Elm Street. Now, that gives you essentially 36 different patterns for every test shot that you fire. And since they fired test shots from both the Book Depository and the Grassy Knoll, you wind up with a total of 72 different test patterns. That of course, will increase the chances or odds of getting a match to the patterns that are on a police recording.

Now, if by chance, you happen to get a match, and then, by chance, you happen to get all five of the sounds, because five of the sounds of the police recording matched the test shots fired in Dealey Plaza. They should be a nonsensical order if these are not Dealey Plaza echo patterns. Now since you have 36 microphone locations, if you had five matches, they would be in random order, but if they are the gunshots that killed President Kennedy, they will have to be in, uh -

REX: Right, in the order of the direction -

DON: In chronological order as the topological order of the microphones, and that's what happened. The very first sound on the recording that matched with a test shot matched to a microphone near the intersection of Houston and Elm Street. The second one matched at the intersection itself, and then third one matched slightly - the very next microphone in order, which was slightly up Elm Street from Houston. Then the fourth and the fifth matched at two microphone locations about 80 feet further up on Elm Street. So they were ordered in respect to numerical order, the chronological order matched the numerical order. But not just the one, two, three, four, five chronological order - the actual spacing was the same. By that, I mean on the tape recording the five sounds, the first three are close together, about a second apart. Then there's a five second gap, and you have two more sounds, about a second apart.

On the street, where you had your microphones, it was three microphones in a row near the intersection of Elm and Houston, and then you skipped about 80 feet - you skipped four microphones, and then you had two microphones next to each other had the last two shots. So the spacing matched - the topological spacing matched the spacing on the recording.

REX: That seems -

DON: And then -

REX: I'm sorry - that seems pretty powerful. I'm curious if there's been a counter argument to that or whether that's -

DON: No, this argument's never been countered. In fact, it's not just the spacing and the order, it's the trajectory, because the spacing between the first microphone match and the last microphone match was about a hundred and thirty feet. And the time on the recording between the first shot and the last shot is eight point three seconds.

Now, in order to go 130 feet in 8.3 seconds, you would have a speed of approximately 12 miles an hour. We know that the Zapruder film show that the President's limousine was going 11.5 miles an hour on Houston Street. So, you have a precise match in the trajectory which was demonstrated by the order of the matching that is completely non-random. It's really that order in the data that convinced the acoustical experts, and not just the matching, that these were the gunshots that killed President Kennedy.

And, of course, this provides us with a test, because now we can go back to the films of Dealey Plaza during the time of the assassination, and look for a motorcycle, and see if there was a motorcycle at the right place and the right time that was predicted by this acoustical evidence. And when they do, they find this, out of the 18 motorcycles that were in the motorcade, the filmed evidence eliminates all but one guy, a police officer named McLaine.

And it turns out that when he was interviewed by the House Select Committee, he was asked, "have you ever had any problems with this radio system?" and he said, "yeah, my microphone used to stick open on me all the time."

So, you know, this sort of evidence, where you have - where you can pinpoint the motorcycle - now I should say that we don't - the evidence is not strong enough to say he's exactly at the right spots, because what the films show, they show him a few seconds before the shooting, and they show him about 15 seconds after the shooting.

From his position, we can say that he is the one cop that was in the right place - that he could have been in the right place at the right time.

In the 1970s, some of America's top acoustic scientists studied the recording and the Dallas crime scene and asserted as fact that it contains sound impulses created by the series of gunshots fired at the presidential motorcade. In other words, this acoustic artifact is a kind of soundtrack for Abraham Zapruder's silent home movie. As the film in Zapruder's eight-millimeter camera captured the sight of gunfire hitting the presidential motorcade, this Dictabelt supposedly captured the sounds of the gunshots.

"If it's true that the sound of gunfire is captured on the recording, then it is conclusive evidence," says Paul Hoch, one of the most respected JFK researchers. "There was a conspiracy."

The tape does not contain the sound of gunfire, said five eminent scientists, in the British forensic journal, Science & Justice, in 2005. In 21 pages of closely argued scientific reasoning, physicist Richard Garwin and four colleagues said a careful analysis of the alleged gun shot sounds on Dictabelt #10 shows that they occurred approximately one minute after Kennedy was killed. They were not gunshots at all. Garwin and his colleagues could not say what created the sound impulses heard on Dictabelt #10.

Their article was a response to a 2001 article in Science & Justice which asserted the reverse: that the Dictabelt certainly captured the sounds of gunshots -- and that one of the shots came from the grassy knoll. That article, written by Don Thomas, an insect specialist at the U.S. Department of Agriculture, reviewed the findings of acoustic scientists retained by the House Select Committee on Assassinations in 1978. They concluded that the tape captured sound impulses created by four gunshots, three from the book depository behind Kennedy's limousine and one from the so-called grassy knoll in front of the motorcade. With some important caveats, Thomas says the HSCA got it right.

So who's right? If you don't care to choose your science on the basis of whether it confirms your pre-existing views on Kennedy's murder, you have to consider the two slightly different arguments going on here.

To oversimplify slightly, Garwin and co. focus on the timing of the supposed shots observed on Dictabelt #10, while Thomas focuses on the nature of the sound impulses found on the recording. On these issues, the dueling scientists reach different conclusions that are logical -- and open to legitimate question.

In my subjective view, Garwin and co. have posed a big problem for Thomas but not so big as to exclude a gun shot from the grassy knoll beyond the limits of plausible conjecture.

After all, we already have the photographic evidence from the Zapruder film showing Kennedy hit by a bullet that snapped his head backwards and drove him sideways into the arms of his wife. To say that a bullet fired from the knoll would have pushed Kennedy backward is well within the limits of plausible conjecture, regardless of what you think about the acoustic evidence. If FBI agents Sibert and O'Neill saw a more massive head wound than what's shown in the autopsy photographs, that too might be more evidence of a shot from the front.

"Don has got to confront a basic problem," says Michael O'Dell, one of the leading experts on the JFK acoustics evidence. "How can a 'shot' be fired from the grassy knoll at the same moment that police are responding to the call 'hold everything secure'? It can't."

O'Dell is an unobtrusively brilliant man who lives with his wife in Fresno, California. By day, he runs the technology department of an insurance company. O'Dell is not one of those people drawn to the assassination by interest in the Kennedys or true crime stories or political conspiracies or the Mafia or anything like that -- and that is a great strength of his work. He does not embody the paranoid style in American politics. He embodies the empirical style sorely lacking in most JFK coverage. His methods are detached, analytical, polite and methodical. His e-mail exchanges with Thomas are civil.

He plays the tape of the shots on his desktop computer. You cannot actually hear the shots amidst the drone of engines and snippets of conversation between various Dallas cops. The screen displays the wave forms of the shots that killed Kennedy. Or not. The scratchy sound of the tape, the spiky green lines, made me think of how narrowly scientific methods captured the reality of a president blasted in the head by a bullet and dying in his wife's arms.

O'Dell focuses on the phenomenon known as "cross talk." First, he explains how the Dallas Police Department (DPD) communications system worked. The DPD operated two radio channels. Channel I was for normal police radio traffic and Channel II was assigned for the use of the presidential motorcade. Each channel was recorded by a different device in the DPD radio room. Channel I was recorded on a Dictabelt and Channel II on a Gray Audograph machine. Both machines worked by engraving a track into a plastic medium. The Dictabelt used a rotating cylinder and the Audograph used a flat disk, similar to a phonograph record. The sounds on the two channels are not synchronized because Channel I was recorded constantly while Channel II was voice-activated.

"Crosstalk occurred when sounds from one channel were picked up by a microphone tuned to the other channel," he explained.

An accident of history created the whole controversy. A DPD motorcyclist somewhere in Dallas "had a defective microphone button that caused it to continuously transmit over a five-minute period during which the assassination took place." This accidental transmission began at 12:28 that day, about two minutes before the assassination.

"If this motorcycle had been part of the motorcade," as one dispatcher thought, "it might" -- emphasize might -- "have picked up sounds of the gunshots" and transmitted them to headquarters where they would have been recorded on Channel I. "If true, those sounds could be used to determine how many shots were fired, their timing, and using echo location methods, where the shots came from."...

Don Thomas is not shaken. He still believes in his 2001 article and its politically loaded conclusion: that Dictabelt #10 captures the sound of a muzzle blast of a gun fired at Kennedy's limousine from the grassy knoll.

"We don't know exactly how the 'hold everything secure' transmission was deposited on the Channel I," he explains. "But we do know there are of lot of skips and jumps caused by the stylus of the dictagraph bouncing out of the groove. You also have to remember the two channels are not synchronized: Channel I is recording constantly from the open microphone on the motorcycle while Channel II is voice activated." This makes determining the timing of all sounds on the recording difficult, if not impossible.

Thomas thinks his critics are straining. "Think about the reality of what they're saying," he says. "They say the grassy knoll shot identified on the recordings is found at the exact moment that Assistant Chief Decker is saying, 'Hold everything secure until we can get homicide investigators up there.' So that must not be the sound of a gunshot. Decker is telling his men, get your ass up on the knoll and see what happened. And these guys are citing that as proof there was no shot from the knoll."

Thomas admits he cannot say exactly how the "hold everything secure" came to be recorded almost simultaneously with the alleged gunshots, but he says Garwin's paper does not change his mind. James Barger, still one the nation's top acoustic scientists, stands by his original findings. "They're talking about corroborative evidence," he says of his critics. "I'm talking about core evidence. I'm trying to explain the five impulses that are on the Dictabelt. We've spent a lot of time debating the timing issues and we'll probably spend a lot more. What they're not talking about is the diabolical coincidence that those impulses matched Barger's recreation both in time and space."

Because the sound matches that Barger found in his Dealey Plaza sound experiment followed a certain pattern, there is an "order of the data" argument that Thomas believes is his trump card. Here's how he puts it in a recent online essay for www.maryferrell.org.