Acoustic Evidence

[Michael T. Griffith]

I recommend that everyone, especially newcomers to the acoustical evidence, read Jason Wakefield's March 2003 article "An In-Depth Study of the Acoustical Evidence in the JFK Assassination." Wakefield's article provides an excellent overview of the history of the acoustical evidence and where research on the dictabelt stood as of 2003.

In 2003, Linsker and his colleagues were still struggling to produce a response to Dr. Don Thomas's 2001 defense of the acoustical evidence in the forensic science journal Science & Justice. The Linsker group submitted a rebuttal to Thomas's article in March 2002 but quickly withdrew it. In reading the draft rebuttal, it is apparent why they withdrew it: it raised only minor points against Thomas's article. They spent three more years working on a response.

In this 2001 article, Dr. Thomas made a convincing case, based on the NRC/NAS panel's calculations for the timing of the transmissions on Channel 1 and Channel 2, that the Bellah "you want" transmission was a far more plausible timing indicator than the Decker "hold everything" transmission, which refuted the NRC/NAS panel's main argument against the acoustical evidence.

It is crucial to understand that the primary scientific argument that the NRC/NAS panel made against the acoustical evidence was that the Decker "hold everything" transmission was crosstalk and that this proved the impulse patterns on the dictabelt were recorded about one minute after the shooting. Until the panel finally looked into Steve Barber's information about the Decker transmission, they had done nothing but manage to reduce the probability of the timing-movement correlations from 99+% to 93% and to reduce the probability of the grassy knoll shot from 95+% to 77.7% (and only by introducing two severe errors into their calculations).

It is even more crucial to understand that the Decker crosstalk hoax was based on the demonstrably false assumption that Channel 2 stopped recording for about 60 seconds. You don't need to be a scientist to understand that if Channel 2 had stopped recording for 60 seconds, the police dispatcher's subsequent time notations would reflect such a pause, but this did not happen. There is no time missing between the 12:30 and 12:32 transmissions, and the 12:35 and 12:36 time notations occur exactly five and six minutes respectively after the 12:30 time notation, proving, at least on this planet, that Channel 2 could not have stopped recording for 60 seconds (nor for 35 seconds). Dr. Thomas:

The linear regression analysis of the dispatcher's time notations proves that the Audograph machine must have shut off for extended times prior to the assassination. But after 12:30, the approximate time of the shooting, the dispatcher's announced times and the actual elapsed time fall into very close agreement for the six minutes after the shooting. There did not seem to be any appreciable amount of time missing, and none between 12:30 and 12:32 when the relevant broadcasts were made and where a full minute of time is supposed to be missing according to the NRC Panel. That is, there is exactly 120 seconds of playback time between the dispatcher's time notations at 12:30 and 12:32. . . .

Note for example (Table 15) that the dispatcher's time notation for 12:32 occurs exactly two minutes after the notation at 12:30. The NRC panel's theory holds that the recorder stopped for a half minute during this interval. It is indeed possible that the real interval between the time notations was actually two and a half minutes apart and by coincidence the lost 31 seconds only makes it appear that no time was lost. But if this were the case, one would expect to see an offset in the time notations downstream. But there is not. The 12:35 and 12:36 time notations fall exactly five and six minutes respectively after the 12:30 time notation, suggesting that the recording is continuous. . . . (Hear No Evil, 2010, pp. 638-639)     

So let us return to the Linsker group and Dr. Thomas's 2001 article. As mentioned, using the NRC/NAS panel's own timing calculations, Dr. Thomas showed that the Bellah "you want" transmission, which the panel acknowledged was crosstalk, was a far more probable timing indicator than the Decker "hold everything" transmission.

In order to refute Dr. Thomas's argument, Linsker and his colleagues had to make a painful admission when they finally submitted their rebuttal in 2005: they had to admit that the NRC/NAS panel's timing calculations were badly off the mark because they had miscalculated the needle-skip adjustment as 60 seconds when in fact it was 35 seconds.

But this was the poster child for a "ruinous victory," i.e., a victory that does fatal damage to the victor. Why? Because, in proving the Bellah crosstalk was not the best time indicator, Linsker and his colleagues were forced to admit that the only way the Decker "hold everything" transmission could be crosstalk was if Channel 2 stopped recording for 35 seconds. This version of the recording-pause theory faced the same unanswerable objection that the NRC/NAS version of the theory faced: a substantial pause on Channel 2, whether 60 seconds, or 44 seconds, or 35 seconds, would cause the dispatcher's subsequent time notations to reflect such a pause, but they do not.

Again, as many scholars have noted, the 12:35 and 12:36 time notations occur exactly five and six minutes respectively after the 12:30 time notation, and there is no time missing between the 12:30 and 12:32 broadcasts. How could this be if Channel 2 stopped recording for 35 seconds? Linsker et al. offered no explanation for why the alleged 35-second pause does not show up in the dispatcher's subsequent time notations. This is one of the facts that caught Dr. David Kaiser's attention and caused him to reject the attacks on the acoustical evidence.

And, as discussed in previous replies, subsequent research by BBN scientists from 2015-2019 has proved that the Decker transmission is an overdub and that the Fisher "I'll check" transmission is crosstalk, which proves that the dictabelt's impulse patterns were recorded during the assassination. Dr. Josiah Thompson discusses this historic new research at length in his book Last Second in Dallas. BBN scientists Dr. James Barger and Dr. Richard Mullen each wrote an appendix for the book.