Gaeton Fonzi: Journalist who investigated the assassination of John F Kennedy

Silvia Odio, a key Kennedy witness, ignored and discredited, told Fonzi: 'We lost. We all lost'

On 29 March 1979, nearly 25 years after the Warren Report was released, the House of Representatives Select Committee on Assassinations (HSCA) issued its own report, concluding that President John Kennedy was "probably" assassinated by Lee Harvey Oswald as part of a conspiracy. The committee's chief counsel, G Robert Blakey, immediately announced, contrary to the report's own equivocations, that "the mob did it". By accepting much of the flawed evidence of the Warren Report, and failing to reach any conclusions of its own, the HSCA report perpetuated the controversy that would not be addressed officially again until the public outcry arising from the Oliver Stone movie JFK prompted the release of thousands of previously classifed files.

Gaeton Fonzi was a reporter hired as an investigator for HSCA, working primarily on connections between Cuban exile groups – and through them, American intelligence agencies – and the assassination. In 1993, in the wake of Stone's film and Gerald Posner's revisionist defence of the Warren Report, he published The Last Investigation, which combined trenchant analysis of the assassination itself with a revealing inside portrait of the machinations and politics behind the HSCA, which led to the failings of its report. It remains one of the very best works on the assassination, notable particularly for its restraint in making no assumptions and drawing no conclusions not backed by evidence. Its quality reflects Fonzi's undoubted skill as a journalist.

Fonzi's path to conspiracy theories grew from his background as an investigative reporter in Philadelphia, where he was born in 1935. He grew up in West New York, New Jersey, but returned to Philadelphia to study journalism and edit the daily paper at the University of Pennsylvania, where he met his future wife Marie. After graduating he worked on the Delaware County Daily and served in the army before joining Philadelphia Magazine in 1959 as a reporter, and later editor.

His most important work was a series, written with Greg Walter, exposing the Philadelphia Inquirer reporter Harry Karafin, who extorted money from businessmen by threatening to write negative stories, claiming to be the "hatchet man" of the Inquirer's powerful owner, Walter Annenberg. Annenberg's use of the paper's power to advance Republican candidates was detailed in Fonzi's 1970 biography, Annenberg, by which time he had sold the Inquirer and been appointed by Richard Nixon as US Ambassador to Great Britain.

When the Warren Report was released, Fonzi originally accepted its conclusions. When the Warren Committee counsel, Arlen Specter, returned to Philadelphia to run for district attorney, he was a natural subject for interview. But Fonzi came across an article by another Philadelphia lawyer, Vincent Salandria, who was among the first critics of the Warren Report, and in particular the "single-bullet" or "magic bullet" theory advanced by Specter. Fonzi studied the case, and, shocked by Specter's inability to defend his findings convincingly, became a sceptic, calling the Warren Report "a deliberate lie" in another Philadelphia Magazine piece.

In 1972 he moved to Miami, where he edited Miami and Gold Coast magazines. In the wake of scandals surrounding the intelligence community, in 1975 the US Senate created what came to be known as the Church Committee, and the Pennsylvania senator Richard Schweiker asked Fonzi to join as an investigator. It was a natural move, two years later, to HSCA, where he was hired by the committee's original counsel, another Philadelphia lawyer, Richard Sprague. As The Last Investigation details, Sprague's refusal to defer to the intelligence community, the CIA in particular, brought him into conflict with his committee heads, and he eventually resigned, to be replaced by G Robert Blakey.

The contacts between Oswald, purportedly a Castro supporter, and the violently anti-Castro Cuban exile community headquartered in Miami, became a natural point of Fonzi's investigations. His crucial discovery was the testimony of Antonio Veciana, leader of the exile group Alpha 66.

Veciana's CIA contact was a man he knew as "Maurice Bishop", and in 1963, Veciana arrived in Dallas for a meeting with "Bishop", to find him conferring with a man he later identified as Oswald. Fonzi was able to show that "Bishop" was in reality David Atlee Phillips, who had also been the CIA's station chief in Mexico City when Oswald was purportedly filmed and recorded at the Soviet consulate there. Veciana would later survive an assassination attempt on him just at the time the HSCA report was released, but the question of why the supposedly communist Oswald would be meeting with a senior CIA agent was never answered by HSCA.

Fonzi's digging into the connections between Cuban exiles and their CIA handlers, as well as mob figures sometimes employed by the CIA, established a prima facie case for conspiracy, and with increasing likelihood, the reality that Oswald was indeed what he said he was, "a patsy". Frustrated by Blakey's failure to pursue these avenues, Fonzi wrote a scathing article for Philadelphia Magazine in 1980, which formed the basis of his book, and became a leading figure in the assassination research community.

He continued to write, for outlets as varied as the New York Times and Penthouse, and served as a lecturer at a number of universities. His work was honoured by more than a dozen awards, including the William Allen White, for investigative journalism, and the Mary Ferrell-JFK Lancer Pioneer award. He died at home, of complications from Parkinson's disease. At the end of The Last Investigation, he quotes Silvia Odio, a key witness ignored and discredited by two government investigations. "We lost," she told him. "We all lost."

Gaeton Fonzi, author and journalist: born Philadelphia 10 October 1935; married Marie (four children); died Satellite Beach, Florida 30 August 2012.