How have ballistic and acoustic analyses for the JFK assassination been validated or challenged by experts?
This fact-check may be outdated. Consider refreshing it to get the most current information.
Executive summary
The acoustic evidence from a Dallas police Dictabelt was central to the 1979 House Select Committee on Assassinations (HSCA) finding that “scientific acoustical evidence establishes a high probability that two gunmen fired” — based on BBN and Weiss & Aschkenasy analyses that identified gunshot-like impulses including one echo-matching a grassy knoll test shot [1] [2] [3]. Subsequent re-analyses split the expert community: National Academy of Sciences and later peer-reviewed work concluded the putative gunshot impulses were recorded about one minute after the shooting and thus not contemporaneous [4], while defenders of the original findings — including Donald B. Thomas and W&A — continue to dispute that timing and statistical critiques [5] [2].
1. The original acoustic claim: a stuck microphone “caught” extra shots
In 1978 the HSCA commissioned Bolt, Beranek & Newman (BBN) and then Weiss & Aschkenasy to study Dallas police radio recordings; BBN’s echo-correlation work and W&A’s modeling identified impulsive sounds with Dealey Plaza gunfire waveforms and concluded there was a high probability of at least one shot from the grassy knoll in addition to shots from the Texas School Book Depository — a finding the HSCA cited directly [1] [3] [6].
2. How the acousticians linked impulses to locations
BBN’s method matched impulse/echo patterns from the Dictabelt to test shots fired in Dealey Plaza and used timing and echo geometry to place a microphone and rifles relative to the motorcade; W&A reported a ~95% probability for a grassy knoll shot based on their acoustic model [7] [2] [6]. The Dictabelt evidence depended on an interpretation that a motorcycle officer’s stuck-open microphone had recorded Dealey Plaza sound at the moment of the assassination [8] [7].
3. The National Academy of Sciences rebuttal: timing matters
A National Research Council / Committee on Ballistic Acoustics review — and a follow-up peer-reviewed reanalysis in Science & Justice — identified serious errors in the Thomas rebuttal and reaffirmed that the alleged “shot” sounds on Channel 1 were recorded roughly one minute after the assassination, not contemporaneously with emergency radio traffic, undermining the HSCA’s assertion that those impulses documented an extra shooter [4] [9].
4. Continued challenges: statistics, artifacts and alternative readings
Statistical critics argued the HSCA and some acoustic teams made invalid assumptions about alarm independence and probability models (chi-square issues and chance matches), and other investigators found the impulses were not unusually different from background noises or could come from recording artifacts such as groove repeats, heterodynes, or playback issues [9] [10] [11]. A private 2013/2014 re-study by Sonalysts, commissioned by Larry Sabato, concluded the stuck microphone could not have recorded assassination sounds — a clear rebuke of the HSCA acoustic case [12] [6].
5. Counter-rebuttals and unresolved expert disagreement
Donald B. Thomas and other acoustics proponents have published peer-reviewed work and books challenging the NAS and Sonalysts conclusions, asserting synchronization errors in the NRC review and defending the original echo-correlation identifications; those publications renewed debate and prompted further peer scrutiny [5] [13]. Likewise, some later expert panels in 2005 reexamined earlier analyses and reported errors in Thomas’ work, illustrating that acoustical interpretation remains contested among qualified specialists [14] [4].
6. Ballistics validation: physical evidence and modern techniques
Separate from acoustics, ballistic and wound‑ballistic analyses have been repeatedly evaluated. The Warren Commission and later experts performed trajectory, gun and cartridge identification and wound ballistics tests supporting shots from the Texas School Book Depository; modern tool‑mark and 3D scanning efforts (NIST, Haag, Leica teams) have produced high‑resolution digital replicas and computational reconstructions that test single‑bullet and cranial‑shot mechanics with contemporary methods [15] [16] [17]. Those ballistic studies generally support the feasibility of shots from the depository but do not settle acoustical claims of a second shooter [16] [18].
7. What the evidence actually supports and what it does not
Available sources show the HSCA leaned heavily on acoustic analyses to infer a “high probability” of a second shooter [3], but subsequent NAS and independent re‑analyses concluded the specific Dictabelt impulses were probably recorded after the assassination and therefore do not provide persuasive contemporaneous confirmation of an extra gunman [4] [12]. Sources do not provide a single, universally accepted resolution; expert opinion remains divided and many critiques focus on timing, statistical assumptions and recording artifacts rather than on the raw waveform matches alone [9] [10].
Limitations: this account uses only the supplied sources. For remaining open questions — e.g., whether newly released 2025 records change acoustic synchronizations — available sources do not mention definitive new acoustic confirmations [19].