stripping away the blackouts of history
Unredacted Logo

Unredacted Episode 4: Interview with Don Thomas

Welcome to Unredacted, the MFF's interview show featuring authors and experts on the Kennedy assassination and related topics. Our fourth episode is an interview with Don Thomas, who reignited debate about the acoustics evidence in 2001, in a paper published in the journal Science and Justice. Since then, Dr. Thomas has done additional studies validating and extending the House Select Committee's work on this issue, presenting at conferences and engaging the critics of this analysis.

At issue is the meaning of impulses on a police dictabelt, recorded due to a stuck-open motorcycle microphone. The House Select Committee on Assassinations hired two groups of experts to analyze the dictabelt, and the result was at least four shots in Dealey Plaza, including one from the infamous "grassy knoll." This finding was largely responsible for the HSCA's conclusion that "President John F. Kennedy was probably assassinated as a result of a conspiracy."

The HSCA's acoustic analysis was soon rebutted, first in an FBI report and then in the report of the "Ramsey Panel," appointed by the National Academy of Sciences. The Ramsey Panel argued that the statistics had been miscalculated, so that the 95% probability threshold had not been reached, and also that crosstalk between the recording and a second police channel showed that the impulses were not coincident in time with the gunfire in Dealey Plaza.

Thomas' paper in Science and Justice found errors in the Ramsey Panel's statistics, and recalculated the statistical probability to a level over 96%. Further, Thomas rebuts the crosstalk timing issue as well as other arguments, such as the location of the police motorcycle at the crucial moments in question.

The interview is a general introduction to Thomas' work on the acoustics evidence, and discusses the sequence of the shots in Dealey Plaza as laid down on the police dictabelt.

Listen to the interview: (34 min)           Read Interview Transcript

Essays by Don Thomas

Echo correlation analysis and the acoustic evidence in the Kennedy assassination revisited by Don Thomas. This is the 2001 paper that revived debate about the acoustics.

Hear no Evil: The Acoustical Evidence in the Kennedy Assassination is a discussion of the acoustics evidence intended for a more general audience.

Crosstalk: Synchronization of Putative Gunshots with Events in Dealey Plaza is the text of a talk given by Don Thomas at the 2002 JFK Lancer November in Dallas conference.

Overview and History of the Acoustical Evidence in the Kennedy Assassination Case is a 3-part essay published by the MFF, in which Thomas describes the history and science of the acoustics, along with the challenges to it.

Other Essays on the Acoustics Evidence

The Acoustic Evidence in the Kennedy Assassination by Michael O'Dell. O'Dell is one of the prominent critics of the acoustic analysis done by the HSCA and Thomas.

Double Decker by Stephan Barber. Barber noticed the occurrence of crosstalk between two channels of the police recordings, and argues that the crosstalk proves that the impulses on the recording can't be Dealey Plaza gunfire.

Reports and Documents on the Acoustics

HSCA Report, Volume VIII. The first half of volume VIII of the HSCA's report contains the reports on the acoustics analyses.

Report of the Committee on Ballistics Acoustics. This report of the so-called "Ramsey Panel" was issued in 1982, a few years after the HSCA's report, and attempted to refute the HSCA's work.

HSCA Report, Volume V, p.499. Volume V contains hearings conducted by the HSCA on December 29, 1978, a few months after the September hearings. These special hearings were used to present the acoustics analysis.

Related Essays and Projects

Silencers, Sniper Rifles & the CIA by Carol Hewitt. While not about the HSCA's acoustics analysis work, this essay discusses the effect that silencers would have had on earwitness testimony about the shots in Dealey Plaza.

Dealey Plaza Witness Database

Stewart Galanor, author of Cover-Up, created the Dealey Plaza Witness Database, hosted on the History Matters website. This interactive tool presents 216 witnesses who were in Dealey Plaza. It shows the location of each person at the time of the shooting, summarizes their statements in the aftermath, and provides direct links to the reports containing those statements. This invaluable tool provides easy access to what "earwitnesses" said about the number and origin of shots.

Starting Points

Acoustics Evidence is a gateway to essays and other resources on the acoustics evidence.

Don Thomas Presentation on the Acoustics Evidence

These 3 video clips are taken from a presentation on the acoustics evidence given by Don Thomas in San Francisco in 2006.

play part 1 (running time: 17:36)
play part 2 (running time: 20:20)
play part 3 (running time: 12:17)

© Mary Ferrell Foundation. All Rights Reserved. |Site Map |MFF Policies |Contact Us