Garrison remains a controversial figure. Opinions differ as to whether he uncovered a conspiracy behind the John F. Kennedy assassination but was blocked from successful prosecution by a federal government cover up, whether he bungled his chance to uncover a conspiracy, or whether the entire case was an unproductive waste of resources.
Once in office, Garrison cracked down on prostitution and the abuses of Bourbon Street bars and strip joints. He indicted Dowling and one of his assistants with criminal malfeasance, but the charges were dismissed for lack of evidence. Garrison did not appeal. Garrison received national attention for a series of vice raids in the French Quarter, staged sometimes on a nightly basis. Newspaper headlines in 1962 praised Garrison's efforts, Quarter Crime Emergency Declared by Police, DA. — Garrison Back, Vows Vice Drive to Continue — 14 Arrested, 12 more nabbed in Vice Raids. Garrison's critics often point out that many of the arrests made by his office did not result in convictions, implying that he was in the habit of making arrests without evidence. However, assistant DA William Alford has said that charges would more often than not be reduced or dropped if a relative of someone charged gained Garrison’s ear. He had, said Alford, “a heart of gold.”
After a conflict with local criminal judges over his budget, he accused them of racketeering and conspiring against him. The eight judges charged him with misdemeanor criminal defamation, and Garrison was convicted in January 1963. (In 1965 the U.S. Supreme Court overturned the conviction and struck down the state statute as unconstitutional.) At the same time, Garrison indicted Judge Bernard Cocke with criminal malfeasance and, in two trials prosecuted by Garrison himself, Cocke was acquitted.
Garrison charged nine policemen with brutality, but dropped the charges two weeks later. At a press conference he accused the state parole board of accepting bribes, but could obtain no indictments. He accused the state legislature of the same, but held no investigation. He was unanimously censured by the legislature.
In 1965, running for reelection against Judge Malcolm O'Hara, Garrison won with 60 percent of the vote.
New Orleans D.A. Jim Garrison began an investigation into the assassination of President Kennedy in the fall of 1966, after receiving several tips from Jack Martin that a man named David Ferrie may have been involved in the assassination. The end result of Garrison's investigation was the arrest and trial of New Orleans businessman Clay Shaw. Garrison's key witness against Clay Shaw was Perry Russo, a twenty-five year old insurance salesman from Baton Rouge, Louisiana. During the trial, Russo testified that he had attended an "assassination party" at David Ferrie's apartment, where Shaw, Ferrie, and Lee Harvey Oswald had discussed killing President Kennedy.
Russo’s version of events has been questioned by some historians and researchers, such as Patricia Lambert, once it became known that part of his testimony was induced by hypnotism, and by the drug Sodium Pentothal (sometimes called "truth serum"). Indeed, the early version of Russo's testimony, as told in the DA memo, before he was subjected to Sodium Pentothal and hypnosis, fails to mention an "assassination party" and says that Russo met Clay Shaw on two occasions, neither of which occurred at the "party. However in Jim Garrison's book On the Trial of the Assassins, he says Russo has already told of the party at David Ferrie's before any "truth serum" was admitted. The jury didn't see enough evidence to convict Shaw. A verdict of not guilty was given.
In 1978, the House Select Committee on Assassinations found that Lee Harvey Oswald's stint in the New Orleans Civil Air Patrol fit the timeline of David Ferrie's Civil Air Patrol service. Committee investigators also found six witnesses whose statements led them to believe that Oswald had been present at Civil Air Patrol meetings headed by David Ferrie.
In 1993, the PBS television program Frontline obtained a group photograph, taken eight years before the assassination, that showed Oswald and Ferrie at a cookout with other Civil Air Patrol cadets. However, as Frontline executive producer Michael Sullivan said, "one should be cautious in ascribing its meaning. The photograph does give much support to the eyewitnesses who say they saw Ferrie and Oswald together in the C.A.P., and it makes Ferrie's denials that he ever knew Oswald less credible. But it does not prove that the two men were with each other in 1963, nor that they were involved in a conspiracy to kill the president." However, Ferrie flat out denied ever knowing Oswald or Shaw, despite several witnesses who claimed to see the three of them in much of 1963.
HSCA Chief Council G. Robert Blakey wrote, in his book The Plot to Kill the President, that the Committee "...was inclined to believe that Oswald was in Clinton [Louisiana] in late August, early September 1963, and that he was in the company of David Ferrie, if not Clay Shaw" and that numerous witnesses in Clinton, Louisiana "...established an association of undetermined nature between Ferrie, Shaw and Oswald less than three months before the assassination."
In a 1992 interview, Edward Haggerty, who was the judge at the Clay Shaw trail, stated: "I believe he [Shaw] was lying to the jury. Of course, the jury probably believed him. But I think Shaw put a good con job on the jury.
In 1973, Garrison was tried for accepting bribes to protect illegal pinball machine operations. His own chief investigator testified that Garrison had received approximately $3,000 every two months for nine years from the dealers. Garrison's defense was that the U.S. government sought to destroy him because of his efforts to implicate the CIA in the Kennedy assassination. The jury agreed. In 1973, Garrison was defeated for reelection as district attorney by Harry Connick, Sr.. In 1978, he was elected as a state Circuit Court of Appeals judge and served in this capacity until his death.
After the Shaw trial, Garrison wrote three books on the Kennedy assassination, A Heritage of Stone (1970), The Star Spangled Contract, and the best-seller, On The Trail of The Assassins (1988).
The 1991 Oliver Stone film JFK was largely based on Garrison's book On The Trail of The Assassins as well as Jim Marrs' Crossfire: The Plot That Killed Kennedy. Kevin Costner played a fictionalized version of Garrison in the movie. Garrison himself had a small on-screen role in the film as United States Supreme Court Chief Justice Earl Warren.
Garrison was also the subject of the song "Keep A Workin' Big Jim" by Johnny Rebel.
Despite being the only district attorney to bring a suspect to trial for conspiring to murder President Kennedy, Garrison was later viewed as an embarrassment by a few conspiracy researchers. However, several researchers have defended Garrison including Jim DiEugenio, William Davy, and Joan Mellen.
According to a number of critics, Garrison was cruel and mistreated witnesses in his attempt to prove an assassination conspiracy. Witnesses, including Perry Raymond Russo later claimed to have been bribed and threatened with perjury and contempt of court charges by Garrison in order to make his case against Shaw. However, in seeming contradiction to this, Perry Russo, in an interview with public radio station reporters Will Robinson and Marilyn Colman, had this to say: "...[NBC News reporter] Walter Sheridan tells me and threatens me that he's gonna take Garrison out and take me with him.
The Garrison investigation had largely faded into obscurity, until Oliver Stone's film was released in 1991, which depicted Garrison as a hero.