Gaeton Fonzi was born in Philadelphia on 10th October, 1935. He attended public schools in West New York, New Jersey, and graduated as an honors journalism major from the University of Pennsylvania in 1957. He served as a commissioned officer in the US Army Infantry and in a Civil Affairs reserve unit. He worked briefly as a general assignment reporter with the Delaware County Daily Times and as an associate editor with the Chilton Company.
In 1959 Fonzi joined Philadelphia Magazine where he later was named Senior Editor. Herbert Lipson, the son of the owner of the magazine, claims that: "In those days, we wanted to cure all the ills of the world and it could take him years... to gather enough to finally publish an investigation." This included the exposure of Harry J. Karafin, a reporter for the Knight-Ridder chain of newspapers. According to According to Walter F. Naedele of the Philadelphia Inquirer, Fonzi "authored a lengthy piece accusing Harry J. Karafin of having extorted money from his subjects in exchange for not publishing stories about their misdeeds.... It was a piece that led to Mr. Karafin's indictment and imprisonment."
It has been argued that Fonzi was "the first to turn regional magazines into investigative instruments". He was also interested in national stories. Fonzi became a harsh critic of the Warren Report. In an article for Philadelphia Magazine he wrote, "The Warren Report is a deliberate lie. The Warren Commission's own evidence proves there was a conspiracy to murder President Kennedy."
In 1972 he became editor of Miami Magazine and senior editor of its sister publication, Gold Coast . Fonzi won the magazine's first national journalism award and wrote more than 100 major feature articles, including two book-length specials. Bernard McCormick, a fellow reporter on the magazine, commented that Fonzi's "gentle, slow talking, sometimes inaudible manner belied his aggressive journalistic style". McCormick claimed Fonzi "joked that his mumbling, halting interview technique worked to his advantage when subjects couldn't stand his pace and blurted out information." During this period he also published Annenberg: A Biography of Power.
In 1975 Senator Richard Schweiker, a member of the Senate Select Committee on Intelligence, asked him to join his staff investigating the assassination of President John F. Kennedy. Two years later Fonzi was invited to join the House Select Committee on Assassinations as a staff investigator. As a special team director, he wrote and edited a major appendix, Volume X, of the Committee's Final Report. His book-length feature article for Washingtonian magazine, detailing the political limitations of the Committee's investigation, received national coverage and resulted in a record readership issue for the publication.
In 1993 he published The Last Investigation, a book detailing his research into the assassination. It is considered by many critics as among the best books on the JFK assassination and is currently recognized as an authority on those aspects of the assassination involving anti-Castro Cubans and the intelligence agencies. As Paul Vitello pointed out in the The New York Times: "He (Fonzi) chronicled the near-blanket refusal of government intelligence agencies, especially the C.I.A., to provide the committee with documents it requested. And he accused committee leaders of folding under pressure - from Congressional budget hawks, political advisers and the intelligence agencies themselves - just as promising new leads were emerging."
In the book Fonzi criticized G. Robert Blakey, the chief counsel and staff director of the House Select Committee on Assassinations for being overly deferential to the CIA. Blakey now accepts that Fonzi was probably right about this. Blakey was shocked in 2003 when declassified CIA documents revealed the full identity of the retired agent who had acted as the committee’s liaison to the agency, George Joannides, who had also overseen a group of anti-Castro Cuban exiles in Dallas in the months before the assassination, when Lee Harvey Oswald was in contact with them. Blakey issued a statement where he said: "I am no longer confident that the Central Intelligence Agency co-operated with the committee.... I was not told of Joannides' background with the DRE, a focal point of the investigation. Had I known who he was, he would have been a witness who would have been interrogated under oath by the staff or by the committee. He would never have been acceptable as a point of contact with us to retrieve documents. In fact, I have now learned, as I note above, that Joannides was the point of contact between the Agency and DRE during the period Oswald was in contact with DRE. That the Agency would put a 'material witness' in as a 'filter' between the committee and its quests for documents was a flat out breach of the understanding the committee had with the Agency that it would co-operate with the investigation."
Throughout his career, Fonzi has written for New York Times Magazine, Esquire, Penthouse, Avenue Magazine, the New York Daily New and the Chicago Tribune. Fonzi has won numerous awards including the Philadelphia Business Club Award, the Philadelphia Bar Association Award, two local Sigma Delta Chi Awards, a National Sigma Delta Chi Award, Four Florida Magazine Association Awards, a City Regional Magazine Association Award, a Florida Atlantic University Enterprise Reporting Special Award, a Washington Monthly Award. Fonzi was a finalist in Columbia's National Magazine Awards and has received the William Allen White Investigative Journalism Award from the University of Kansas. He has been a guest lecturer at the University of Pennsylvania, University of Michigan, and Stetson University.
Gaeton Fonzi, an avid runner and sailor, he lived in Florida with Marie, his wife of 55 years. They had four children, eight grandchildren, and two great-grandchildren. He was also a member of the South Florida Researchers' Group.