JFK Witness Testimony on Hearing a Double Bang: A Math Analysis
Feb. 8, 2014
Updated: May 21, 2014
In the article The Guns of Dealey Plaza by John S. Craig, the author lists 22 individuals who testified they heard a “double bang”: the final two of three shots occurred nearly simultaneously.
If Oswald was the only shooter there would have been at least 2.3 seconds between shots, assuming he used the telescopic sight found on the Mannlicher Carcano.
If we assume a 0.50 probability ( a fair assumption) that a given witness was correct in hearing two shots fired nearly simultaneously, then the probability of the witness being mistaken is also 0.50. The probability that ALL 22 witnesses listed below were mistaken is P= 0.5^22 = 0.000000238 or 1 in 4 million.That is also the probability that Oswald fired the shots, since the Carcano, a bolt-action rifle, was incapable of being fired at “double-bang” speed.
Assume p= 0.5 is the probability that a given witness was correct in hearing shots or seeing smoke from the grassy knoll and 1-p = 0.5 the probability the witness is mistaken).
Andrew Mason determined that at least 44 witnesses heard a double bang. The probability all 44 would be mistaken is P=.5^44 = 5.7E-14 (1 in 17 trillion). http://www.dufourlaw.com/JFK/shot_pattern_excerpt.PDF
Let N = the number of witnesses who claimed shots came from the grassy knoll.
The Double Bang
John Craig wrote:
The Warren Commission’s official conclusion concerning the “Number of Shots” states that all the shots were fired from the sixth-floor window at the southeast corner of the Texas School Book Depository Building.  The Commission stated that a consensus among witnesses at the scene was that three shots were fired, though some heard two shots and others heard four and perhaps as many as five or six shots. 
Numerous descriptions of the last two shots by so many witnesses leaves doubt as to whether Oswald was physically capable of firing both of the shots that so many characterized as being shot almost simultaneously, if not “automatically.”
It was the Commission’s belief that (a) one shot passed through the President’s neck and caused all of Governor Connally’s wounds, (b) a subsequent shot hit the President’s head, (c) no other shot struck any part of the automobile, and (d) three shots were fired with one missing, though which one missed is unknown.  “Two bullets probably caused all the wounds suffered by President Kennedy and Governor Connally. Since the preponderance of the evidence indicated that three shots were fired, the Commission concluded that one shot probably missed the Presidential limousine and its occupants, and that the three shots were fired in a time period ranging from approximately 4.8 to in excess of seven seconds.” 
FBI tests for the Warren Commission found that a 6.5 Mannlicher Carcano, bolt-action rifle, Model 91/38 required a minimum of 2.3 seconds to fire two shots.  The HSCA made tests in which the telescopic sight was removed to see how fast the rifle could be fired without aiming. Its tests resulted in firings of 1.65, 1.75, and just over two seconds.  The only way that the rifle could be fired this quickly was to simply maneuver the bolt action as fast as possible and shoot. The tests were not done with Oswald’s Mannlicher Carcano. Whether Oswald’s rifle was in a condition where it could be tested is questionable since “the pressure to open the bolt was so great that we tended to move the rifle off the target,” according to one of the Warren Commission testers. 
If Oswald were the only shooter there would have to be at least 2.3 seconds between shots, assuming he used the telescopic sight found on the Mannlicher Carcano. The three shots that the Warren Commission claimed were fired from Oswald’s rifle could not have been shot faster than 6.9 seconds, including the minimum of 2.3 seconds to set for the first shot. Secret Service Agent Roy Kellerman described the shots as a “flurry.” Two of the shots were often described by witnesses as so closely spaced that they seemed “simultaneous” and had “practically no time element between them.” Additionally, there is a substantial amount of testimony, presented in this article, that describes the later shots as sounding different from the first shot. Governor Connally’s initial reaction to the gunfire was “that there were either two or three people involved or more in this or someone was shooting with an automatic rifle.” 
A double sound, or bang, is described by three Secret Service agents. Two of these agents sat within feet of Kennedy as occupants of the limousine. A double shot was reported by one of the witnesses standing on the overpass.
1. Special Agent William Greer, the limousine driver, testified that “the last two shots seemed to be just simultaneously, one behind the other.” .
2. Secret Service Roy Kellerman sat next to Greer and was intimately familiar with the sound of weapons. Kellerman testified: ” Let me give you an illustration … You have heard the sound barrier, of a plane breaking the sound barrier, bang, bang? That is it. It was like a doublebang — bang, bang.” 
3. Special Agent George Hickey (in reference to the second and third shots). “At the moment he was almost sitting erect I heard two reports, which I thought were shots and that appeared to me completely different in sound than the first report and were in such rapid succession that there seemed to be practically no time element between them.” 
4. Special Agent Clint Hill told the Commission that the second noise he heard was different from the first shot ” … like the sound of shooting a revolver into something hard… almost a double sound.” 
5. S.M. Holland carefully watched the motorcade from the railroad overpass. He heard four shots with the third and fourth sounding like a “double shot.” He thought some of the shots came from behind the fence on the grassy knoll.
6. Deputy Sheriff Roger Craig: “The first shot … sort of like it reverberated … well, it was quite a pause between there [the first and second shots] … It could have been a little longer [than two or three seconds]… ” Between the second and third shots there was “no more than two seconds. It was–they were real rapid.” 
6. Joe R. Molina, witness “… Of course, the first shot was fired then there was an interval between the first and second, longer than the second and third.” 
7. DPD Seymour Weitzman. “First one, then the second two seemed to be simultaneously.” 
8. Ladybird Johnson. ” … suddenly there was a sharp loud report–a shot. It seemed to me to come from the right, above my shoulder, from a building. Then a moment and then two more shots in rapid succession.” 
9. Secret Service Special Agent Forrest V. Sorrels. “There was to me about twice as much time between the first and second shots as there was between the second and third shots.” 
10. Congressman Ralph W. Yarborough. “… by my estimate–to me there seemed to be a longer time between the first and second shots, a much shorter time between the second and third shots…
11. Dallas Mayor Earle Cabell. “There was a longer pause between the first and second shots than there was between the second and third shots. They were in rather rapid succession.” 
12. Secret Service Special Agent Sam A. Kinney. “I saw the President lean toward the left and appeared to have grabbed his chest with his right hand. There was a second of pause and then two more shots were heard … ” 
13. Special Agent William A. McIntyre. “The Presidential vehicle was approximately 200 feet from the underpass when the first shot was fired, followed in quick succession by two more.
14. Special Agent Warren W. Taylor. “In the instant that my left foot touched the ground, I heard two more bangs and realized that they must be gun shots.” 
15. Linda Willis. “Yes, I heard one. Then there was a little bit of time, and then there were two real fast bullets together. When the first one hit, well, the President turned from waving to the people, and he grabbed his throat, and he kind of slumped forward, and then I couldn’t tell where the second shot went.” 
16. Special Agent Rufus Youngblood. “There seemed to be a longer span of time between the first and the second shot than there was between the second and third shot.”  ” … from the beginning at the sound of the first shot to the second or third shot, happened with a few seconds.” 
17. Robert Jackson. “I would say to me it seemed like three or four seconds between the first and the second, and between the second and third, well, I guess two seconds, they were very close together … ” 
18. Arnold Rowland. “The actual time between the reports I would say now, after having had time to consider the six seconds between the first and second report and two between the second and third.” 
19. Luke Mooney. “… The second and third shot was pretty close together, but there was a short lapse there between the first and second shot.” 
20. Ms. Mitchell (Mary Ann Mitchell). “… there were three—the second and third being closer together than the first and second … ” 
21. Lee Bowers “I heard three shots. One, then a slight pause, then two very close together … also reverberation from the shots.” 
22. Jean Hill. “There were three shots — one right after the other, and a distinct pause, or just a moment’s pause, and I heard more … ” And concerning the shots that followed the first three Ms. Hill said they were “quicker — more automatic.”