The committee found that it could not exclude the possibility that individual members of the national syndicate of organized crime or anti-Castro Cubans were involved in a probable conspiracy to assassinate President Kennedy.

With the rapidly growing body of assassination conspiracy material, public trust in the findings of the Warren Commission report was declining.

[16] There was also significant public interest after a video segment of the Zapruder film was first shown on TV on March 6, 1975, during the ABC late-night television show Good Night America,[17] after being stored by Life magazine out of view for almost twelve years.

The footage showed the president's head recoiling violently backwards inside the presidential limousine during the fatal shooting as Lee Harvey Oswald was more than 80 yards behind.

In comparison to witness testimony and government documents, the committee felt that such investigations would particularly benefit from the scientific advances of the fifteen years since the Warren Commission.

(See single bullet theory)[20][21][22][23] Additionally, the location of the shooter (at the 6th floor Texas School Book Depository window) was determined using trajectory analysis.

Forensic anthropologists as well as photographic and radiographic experts, based on unique anatomical details, verified that JFK's autopsy photos and x-rays were only of the late president.

[19]: Vol VII, 41 The HSCA's Forensic Pathology Panel included Michael Baden, John I. Coe, Joseph H. Davis, George S. Loquvam, Charles S. Petty, Earl Rose, Werner Spitz, Cyril Wecht, and James T.

[24] With the benefit of authenticated photographs, x-rays and notes from the Kennedy autopsy, a nine-doctor panel of expert pathologists reviewed and corroborated the Warren Commission's medical findings.

Although the HSCA medical panel was critical of the thoroughness and methodology of the original autopsy,[25]: 382–386  they concurred, although Cyril Wecht dissented, with the Warren Commission's conclusion that two, and only two bullet wounds entered from above and behind (the direction of Oswald in the Book Depository).

During the parade in Houston, the HSCA noted that 33 motorcyclists – including 6 on the flanks of the same presidential limousine- were deployed throughout the journey, which was not the case in Dallas 24 hours later.

"[27] Although the HSCA had prepared a draft report confirming the Warren Commission's single shooter theory and finding no evidence of conspiracy, at the eleventh hour, the committee was swayed by a since-disputed acoustic analysis of a dictabelt police channel recording.

[11]: 495  This acoustic analysis of the dictabelt recording by the firm Bolt, Beranek and Newman Inc. concluded that four shots were fired at the president, thus causing the HSCA to reverse its earlier position and report "that Kennedy was probably assassinated as a result of a conspiracy.

[11]: 84 As recommended by the HSCA, the Justice Department reviewed those findings through the FBI's Technical Services Division and by contracting the National Academy of Sciences, which specially appointed the Committee on Ballistic Acoustics (CBA).

Although the HSCA publicly released its findings in 12 volumes and a single-volume summary report, the majority of primary documents were sealed for 50 years under congressional rules.

In 1992, Congress passed legislation to collect and open up all the evidence relating to Kennedy's death, and created the Assassination Records Review Board to further that goal.

[25]: Endnotes 149 The ARRB reported: "Because the HSCA investigation was marked by internal squabbling and disillusioned staffers, the committee's records were the subject of ongoing controversy.

Chief Counsel Blakey later stated that Joannides should have in fact been interviewed by the HCSA, rather than serving as a gatekeeper to the CIA's evidence and files regarding the assassination.

[46]According to a 2015 Politico report,[47] newly declassified documents show that CIA director John A. McCone hid evidence from the Warren Commission.