What did the House Select Committee on Assassinations actually conclude about a second shooter and why is it disputed?

1. What the HSCA actually concluded about a second shooter

After reviewing witnesses, films and new scientific studies, the HSCA concluded Oswald fired three shots and that “the fourth shot came from a second assassin located on the grassy knoll, but missed,” leading the committee to state that Kennedy was “probably assassinated as a result of a conspiracy” ^{[1] [2]}. The HSCA’s reversal from an Oswald‑alone draft to a probable conspiracy hinged on a Bolt, Beranek and Newman (BBN) acoustic analysis of a motorcycle police radio dictabelt that the HSCA interpreted as containing four impulses consistent with four gunshots ^{[3] [2]}.

2. Why the acoustic finding was decisive—and fragile

The dictabelt was the HSCA’s sole scientific support for a second shooter; without it the committee’s physical‑evidence chapters pointed to Oswald as the shooter of the fatal wounds ^{[3] [1]}. The BBN study’s claim of four shots was treated as powerful because it appeared to align with witnesses and the Zapruder film’s perceived anomalies, but the dictabelt’s provenance, synchronization to the motorcade timeline, and statistical interpretation were contested from the start—a weakness the HSCA acknowledged by limiting its conspiracy conclusion to “probable” rather than definitive ^{[3] [1]}.

3. Immediate and later technical pushback

Almost immediately critics and dissenters inside the HSCA pushed back: four of twelve committee members formally dissented from the conspiracy finding based on the acoustic evidence and a fifth said further study was necessary ^[3]. Subsequent reviews by the FBI’s Technical Services Division and the NAS Committee on Ballistic Acoustics concluded that “reliable acoustic data do not support a conclusion that there was a second gunman,” undermining the BBN result and prompting the Justice Department to state it found no persuasive evidence of a conspiracy ^{[2] [4] [5]}.

4. Political dynamics, internal squabbling and credibility questions

The HSCA’s work was politically charged and internally fractious; later assessments and the Assassination Records Review Board reported that staff quarrels, leadership decisions and allegedly suppressed or marginalized investigative threads left parts of the record controversial and produced lingering doubts about how fully alternative leads were pursued ^{[2] [1]}. Critics argue the committee’s eagerness to answer public skepticism may have amplified the dictabelt finding, while defenders say the committee responsibly flagged unresolved issues—both views are traceable in the committee record ^{[6] [7]}.

5. What remains uncontested and why the dispute endures

Uncontested in official HSCA documentation is that Oswald fired shots from the Texas School Book Depository; contested is whether acoustic evidence proves a second shooter and whether any identified conspiracy actors existed—HSCA explicitly could not identify other gunmen or the extent of any conspiracy ^{[1] [8]}. Because the conspiracy claim turns on a single, technically complex dataset later judged unreliable by respected scientific reviewers, the committee’s “probable” language created a headline result that many experts judge overreaching while many in the public and some investigators view it as validation of long‑held suspicions—hence the enduring dispute ^{[2] [9]}.