After the war Garrison attended Tulare Law School in New Orleans. He then joined the Federal Bureau of Investigation (FBI) and served as a special agent in Seattle and Tacoma. In 1954 Garrison returned to New Orleans where he became assistant district attorney.
In 1961, Garrison was elected as the city's district attorney. He developed a good reputation and in his first two years he never lost a case. According to Joan Mellen, the author of A Farewell to Justice (2005): "He hired the first woman assistant attorney in New Orleans history, Louise Korns, who had been first in her class at Tulane, and entrusted most of the research to her... Garrison's was the first office to employ full-time police investigators, among them Louis Ivon... Garrison dressed nattily in three-piece suits and he was not corrupt, rejecting the Napoleonic premise that political office was a form of private property."
Three days after the assassination of John F. Kennedy, Garrison brought in David Ferrie for questioning. He had been informed by Jack Martin, a part-time private investigator, that Ferrie had known Lee Harvey Oswald and might have been involved in the assassination. Ferrie told Garrison that on the day of the assassination he had driven to Houston in order to go ice-skating. Garrison thought he was lying and handed him over to the Federal Bureau of Investigation. However, after a brief interview he was released.
In 1965 Garrison was told by Hale Bloggs, a Congressman from Louisiana and a former member of the Warren Commission, that he had serious doubts that Oswald was a lone-gunman. This encouraged Garrison to read the Warren Report and books on the assassination by Mark Lane, Edward Jay Epstein and Harold Weisberg.
Garrison recruited Tom Bethell to investigate the case. He interviewed Vince Salandria who claimed that the conspirators were the CIA and military leaders who wanted to stop President Kennedy's effort to end the Cold War. He also contacted Sylvia Meagher and Mary Ferrell.
In November 1966 Garrison told a journalist, David Chandler, that he had important information on the case. Chandler told Richard Billings and in January 1967, the Life Magazine reporter arranged a meeting with Garrison. Billings told Garrison that the top management at Life had concluded that Kennedy's assassination had been a conspiracy and that "his investigation was moving in the right direction". Billings suggested that he worked closely with Garrison. According to Garrison "The magazine would be able to provide me with technical assistance, and we could develop a mutual exchange of information".
Garrison agreed to this deal and Richard Billings was introduced to staff member, Tom Bethell. In his diary Bethal reported: "In general, I feel that Billings and I share a similar position about the Warren Report. He does not believe that there was a conspiracy on the part of the government, the Warren Commission or the FBI to conceal the truth, but that a probability exists that they simply did not uncover the whole truth."
Garrison also recruited Bernardo de Torres, who had good connections with anti-Castro figures. William Turner, the author of Rearview Mirror: Looking Back at the FBI, the CIA and Other Tails (2001) has argued: "A veteran of the Bay of Pigs, De Torres showed up on Garrison's doorstep early in the probe, saying he was a private detective from Miami who wanted to help, and dropping the name of Miami DA Richard Gerstein, a friend of Garrison's, as an opener. In retrospect, Garrison remembered that every lead De Torres developed ended up in a box canyon." One of the jobs Garrison gave him was to find Eladio del Valle.
Garrison became suspicious of his motives and on 7th January, 1967, he ordered his staff "under no circumstances" to offer any information to De Torres. Four days later he wrote at the top of one of De Torres' memos: "His reliability is not established." Garrison was right to be suspicious as he later discovered he was working for the CIA. According to Gaeton Fonzi, de Torres's CIA handler was Paul Bethel. Another researcher, Larry Hancock, has argued that "It certainly appears that De Torres’ role in the Garrison investigation is suspicious, and it supports Otero’s remarks to HSCA investigators that De Torres had ‘penetrated’ Garrison’s investigation. It also shows that De Torres had an agenda of his own in addition to getting intelligence about Garrison’s investigation and investigators. That agenda involved once again shifting attention to Fidel Castro and a Cuban hit team rather than the activities of the Cuban exiles."
Garrison eventually became convinced that a group of right-wing activists, including Guy Banister, David Ferrie, Carlos Bringuier, Eladio del Valle and Clay Shaw were involved in a conspiracy with the Central Intelligence Agency (CIA) to kill John F. Kennedy. Garrison claimed this was in retaliation for his attempts to obtain a peace settlement in both Cuba and Vietnam.
On 17th February, 1967, The New Orleans States-Item reported that Garrison was investigating the assassination of Kennedy. It also said that one of the suspects was David Ferrie. Five days later Ferrie's body was found in his New Orleans apartment. Although two suicide notes were found, the coroner did not immediately classify the death as a suicide, noting there were indications Ferrie may have suffered a brain hemorrhage.
Garrison immediately announced that Ferrie had been a part of the Kennedy conspiracy. "The apparent suicide of David Ferrie ends the life of a man who in my judgment was one of history's most important individuals. Evidence developed by our office had long since confirmed that he was involved in events culminating in the assassination of President Kennedy... We have not mentioned his name publicly up to this point. The unique nature of this case now leaves me no other course of action." Garrison added that he was making preparations to arrest Ferrie when they heard of his death. "Apparently, we waited too long."
Another suspect, Eladio del Valle, was found dead in a Miami parking lot twelve hours after Ferrie's was discovered in New Orleans. Police reported that de Valle had been tortured, shot in the heart at point-blank range, and his skull split open with an axe. His murder has never been solved. Diego Gonzales Tendera, a close friend, later claimed de Valle was murdered because of his involvement in the assassination of President John F. Kennedy. A senior member of the Cuban Secret Service, Fabian Escalante, agreed: "In 1962 Eladio Del Valle tried to infiltrate Cuba with a commando group of 22 men but their boat had an English key - a little island. In the middle of 1962. Of course, we knew this. I tell you about this, because one of our agents who was one of the people helping to bring this group to Cuba, was a man of very little education. They talked English on many occasions on this little island with Eladio Del Valle told this person, on many occasions, that Kennedy must be killed to solve the Cuban problem. After that we had another piece of information on Eladio Del Valle. This was offered to us by Tony Cuesta. He told us that Eladio Del Valle was one of the people involved in the assassination plot against Kennedy."
A week after the death of David Ferrie Garrison announced the arrest of Clay Shaw. He was 54 years old and a retired businessman. John J. McCloy, a former member of the Warren Commission, was asked by a journalist what he thought about the Garrison investigation. He replied that the Warren Commission had always known that new evidence in the case might turn up. "We did not say that Oswald acted alone. We said we could find no credible evidence that he acted with anyone else."
Ramsay Clark, the new Attorney General stated that the FBI had already investigated and cleared Shaw "in November and December of 1963" of "any part in the assassination". As Garrison pointed out: "However, the statement that Shaw, whose name appears nowhere in the 26 volumes of the Warren Commission, had been investigated by the federal government was intriguing. If Shaw had no connection to the assassination, I wondered, why had he been investigated?" Within a few days of this statement Clark had to admit that he had published inaccurate information and that no investigation of Shaw had taken place.
As part of Garrison's attempt to prove the existence of a conspiracy, he subpoenaed the Zapruder Film from Time-Life Corporation. The company refused and they fought this subpoena all the way to the Supreme Court, which finally ruled that the corporation had to hand over the film. As Jim Marrs has pointed out: "Time-Life grudgingly turned over to Garrison a somewhat blurry copy of the film - but that was enough. Soon, thanks to the copying efforts of Garrison's staff, bootleg Zapruder films were in the hands of several assassination researchers."
In May, 1967 Hugh Aynesworth published a critical article of Garrison in Newsweek: "Garrison's tactics have been even more questionable than his case. I have evidence that one of the strapping D.A.'s investigators offered an unwilling "witness" $3,000 and a job with an airline - if only he would "fill in the facts" of the alleged meeting to plot the death of the President. I also know that when the D.A.'s office learned that this entire bribery attempt had been tape-recorded, two of Garrison's men returned to the "witness" and, he says, threatened him with physical harm."
Garrison later responded to Aynesworth's claims: "As for the $3,000 bribe, by the time I came across Aynesworth's revelation, the witness our office had supposedly offered it to, Alvin Babeouf, had admitted to us that it never happened. Aynesworth, of course, never explained what he did with the "evidence" allegedly in his possession. And the so-called bribery tape recording had not, in fact, ever existed."
In September, 1967, Richard Billings told Garrison that Life Magazine was no longer willing to work with him in the investigation. Billings claimed that this was because he had come to the conclusion that he had links to organized crime. Soon afterwards, Life began a smear campaign against Garrison. It was reported that Garrison had been given money by an unnamed "New Orleans mobster".
In Shaw's trial Perry Russo claimed that in September, 1963, he overheard Clay Shaw and David Ferrie discussing the proposed assassination of John F. Kennedy. It was suggested that the crime could be blamed on Fidel Castro. Russo's testimony was discredited by the revelation that he underwent hypnosis and had been administered sodium pentathol, or "truth serum," at the request of the prosecution. It claimed that Russo only came up with a link between Shaw, Ferrie and Oswald after these treatments. Shaw was eventually found not guilty of conspiring to assassinate Kennedy.
In 1973 Garrison lost the office to Harry Connick. After leaving his post as district attorney Garrison wrote a book about his investigations of the Kennedy assassination, On the Trail of the Assassins (1988). Carl Oglesby summarized Garrison's theory as follows:
(a) Rabidly anti-Communist elements of the C.I.A.'s operations division, often moving through extra-governmental channels, were deeply involved at the top of the assassination planning and management process and appear to have been the makers of the decision to kill the President.
(b) The conspiracy was politically motivated. Its purpose was to stop J.F.K.'s movement toward détente in the Cold War, and it succeeded in doing that. It must therefore be regarded as a palace coup d'etat.
(c) Oswald was an innocent man craftily set up to take the blame. As he put it, "I'm a patsy."
Several researchers were highly critical of the methods that Garrison used in his investigation. Sylvia Meagher wrote: "As the Garrison investigation continued to unfold, I had increasingly serious misgivings about the validity of his evidence, and the scrupulousness of his methods." Anthony Summers was surprised that Oliver Stone decided to base his film JFK on Garrison's work: "From a vast array of scholarship, he picked a book by Jim Garrison, former District Attorney of New Orleans, as his main source work. Garrison, many will recall, is a strange figure - considered crazy by some, and crooked by others."
Jim Garrison died on 21st October, 1992.