Dictabelt evidence relating to the assassination of John F. Kennedy
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The Dictabelt evidence relating to the assassination of John F. Kennedy comes from a Dictabelt recording from a police officer's motorcycle that was escorting Kennedy’s motorcade. John F. Kennedy, 35th (1961–1963) President of the United States was assassinated in Dallas, Texas on November 22, 1963. Many aspects of his assassination have been investigated and the less well-known dictabelt recording has been gaining prominence amongst conspiracy theorists.
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[edit] House Select Committee on Assassinations
In December 1978, the House Select Committee on Assassinations had prepared a draft of its final report which concluded that Oswald had acted alone. However, after hearing testimony regarding the dictabelt recording, they quickly changed their findings and concluded a second gunman had fired a fourth shot at Kennedy (it was claimed that a fourth shot could be heard on the Dictabelt). G. Robert Blakey, chief consul of the HSCA, later said, "If the acoustics come out that we made a mistake somewhere, I think that would end it." Despite serious criticism of the scientific evidence and the HSCA's conclusions, speculation regarding the Dictabelt and the possibility of a second gunman has persisted.
The Dictabelt does not contain audible gunshots, but investigators compared "impulse patterns" on the dictabelt to the recordings of the firing of another Carcano rifle in Dealey Plaza. Based on this, Bolt, Beranek and Newman concluded that there was a 50% chance of a fourth shot originating from the knoll. Mark Weiss and Ernest Aschkenasy of Queens College concluded the probability was 95%.
The HSCA concluded the recording originated from the motorcycle of H.B. McLain, who testified before the committee that his microphone was often stuck in the open position. However, McLain did not hear the actual recording until after his testimony, and upon hearing it he adamantly denied the recording originated from his motorcycle. He said that the other sounds on the tape do not match his movements. Sirens are not heard on the tape until over two minutes after the shooting; however, McLain accompanied the motorcade to Parkland Hospital immediately after JFK was shot, with sirens blaring the entire time.
Other audio discrepancies also exist. Crowd noise is not heard on the Dictabelt recording, despite the sounds generated from the many onlookers in Dealey Plaza. The toll of a bell is heard on the recording, leading some to suggest that it is the replica of Liberty Bell at the Trade Mart (JFK's intended destination) and that the recording is from a motorcycle at that location and not Dealey Plaza.
[edit] Criticism
The adult magazine Gallery published a plastic record of the Dictabelt recording in its July 1979 issue. Ohio rock drummer Steve Barber listened to that recording repeatedly and heard the words "Hold everything secure" at the point where the House Select Committee on Assassinations had concluded the assassination shots were recorded. However, those words were spoken by Sheriff Bill Decker about a minute after the assassination, so the shots could not be when the HSCA claimed.
After the FBI disputed the validity of the acoustic evidence, the Justice Department paid for the National Academy of Sciences to review it. A panel of scientists headed by Dr. Norman Ramsey issued a report in 1982 which agreed with Barber and determined that there was no compelling evidence for gunshots on the recording and that the HSCA's suspect signals were recorded about a minute after the shooting happened.
[edit] Donald Thomas rebuttal
An analysis published in the March 2001 issue of Science & Justice by Dr. Donald Thomas uses a different Dallas policeman radio transmission synchronization to put forth the claim that the National Academy of Sciences panel was in error. Thomas's conclusion, very similar to the HSCA conclusion, is that the gunshots impulses are real to a 96.3% certainty. Thomas presented additional details and support in the November 2001 [1] and September [2] and November [3] 2002 issues.
[edit] Further analysis
In 2003, an independent researcher named Michael O'Dell reported that both the National Academy and Dr. Thomas had used incorrect timelines that, when corrected, showed the impulses happened too late to be the real shots even with Thomas's alternative synchronization. In addition, he showed that, due to a mathematical misunderstanding and the presence of a known impulse pattern in the background noise, there never was a 95% or higher probability of a shot from the grassy knoll.
A November 2003 analysis paid for by the cable television channel Court TV responded that the gunshot sounds did not match test gunshot recordings fired on Dealey Plaza any better than random noise. In December 2003, Thomas responded by pointing out what he claimed were errors in the November 2003 Court TV analysis.
[edit] Digital restoration
In 2003, ABC News aired the results of their investigation on a program called Peter Jennings Reporting: The Kennedy Assassination-Beyond Conspiracy. Based on computer diagrams and recreations done by Dale K. Myers, it concluded that the sound recordings on the Dictabelt could not have come from Dealey Plaza and that the Police Officer H.B. McLain was correct in his assertions that he had not yet entered Dealey Plaza at the time of the assassination.
In the March, 2005 issue of Reader's Digest [4], it was reported that Carl Haber and Vitaliy Fadeyev were assigned with the task of digitally restoring Dictabelt 10 by Leslie Waffen from the National Archives. Their method consisted of using sensors to map the microscopic contours of the tracks of old sound recordings without having to play the originals. Dictabelt 10 was worn from countless playings and cracked due to improper storage. It is hoped that a digitalized version will provide more clarity and thus make the evidence easier to work with.
[edit] References
- Stokes, Louis (Chairman, House Select Committee on Assassinations). (29 March 1979). Report of the Select Committee on Assassinations of the U.S. House of Representatives.
- Ramsey, Norman F. (Chairman, Committee on Ballistic Acoustics, National Academy of Sciences). (1982). Report of the Committee on Ballistic Acoustics.
- Posner, Gerald (1993). Case Closed. Random House. ISBN 0-679-41825-3. (pp. 238-242, unraveling of acoustic evidence in JFK conspiracy finding)
- Thomas, Donald B. (14 June 2000). Echo correlation analysis and the acoustic evidence in the Kennedy assassination revisited. Science & Justice 2001 41, 21-32.
- Thomas, Donald B. (17 November 2001). The acoustical evidence in the Kennedy assassination.
- Thomas, Donald B. (September 2002). Emendations.
- Thomas, Donald B. (23 November 2002). Crosstalk: Synchronization of Putative Gunshots with Events in Dealey Plaza.
- O'Dell, Michael. (2003). The acoustic evidence in the Kennedy assassination.
- Berkovitz, Robert. (19 November 2003). Searching For Historic Noise: A Study of a Sound Recording Made on the Day of the Assassination of President John F. Kennedy.
- Thomas, Donald B. (December, 2003). Impulsive Behavior: The CourtTV - Sensimetrics Acoustical Evidence Study.
- National Research Council, Washington, DC 1982 Report of the Committee on Ballistic Acoustics
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