STRANGE CLAIM: A second gunman on the grassy knoll
The FBI Laboratory's December 1980 review of the acoustic evidence concluded the analyses did not scientifically prove a second gunman fired from the grassy knoll — rendering the House committee's 'high probability of conspiracy' finding invalid.
The HSCA's 1979 'high probability of conspiracy' rested SOLELY on acoustic analysis of the Dallas police Dictabelt recording. The FBI Laboratory review (Dec 1980) found the analyses 'did not scientifically prove' a second gunman — the finding is invalid; later audio research confirmed the open-mike motorcycle wasn't in the motorcade during the shots.
Evidence status: Actively contradicted by primary sources.
AI DOCUMENT REVIEW
Generated from the primary source document. How we review.
AI review of "The Findings of the Federal Bureau of Investigation's Review of the Acoustical Reports Published by the House Select Committee on Assassinations" (FBI Lab, Dec 1980; PDF, 32 pages, ~11,200 words), read in full: - Finding 1 — verbatim: "The analyses of acoustical evidence by Bolt Beranek and Newman, Inc., Mark R. Weiss, and Ernest Aschkenasy did not scientifically prove that a gunshot was fired by a second gunman from the grassy knoll area of Dealey Plaza during the assassination of President Kennedy on November 22, 1963. Therefore, the House Select Committee on Assassination's finding that 'scientific acoustical evidence establishes a high probability that two gunmen fired at President John F. Kennedy' is invalid." - Finding 2: the analyses also "did not scientifically prove that the Dictabelt recording of Channel 1 of the Dallas Police Department radio system contains the sounds of gunshots or any other sounds originating in Dealey Plaza during the assassination." - Method critique: BBN's test firings (12 shots, August 20, 1978, at the Texas School Book Depository and grassy knoll, 36 microphones, 432 test patterns) produced patterns like "badly smudged 'fingerprints'" because the open police-radio microphone sat next to a loud motorcycle engine, and the radio's limiting circuitry distorted loud impulses — "eliminating impulse peaks, changing the position of peaks, and even producing new peaks where no impulse peaks previously existed." - The document addresses the acoustic analysis only — it does not rule on any other conspiracy evidence. Record summary verified accurate against the document.