Upon returning again to civilian life, Garrison worked in several different trial lawyer positions before being appointed as an assistant district attorney in New Orleans. He served in that role from 1955 to early 1958, In the runoff election, Garrison scored an upset win by 6,000 votes. Handicapped by a lack of major political backing, he had saved his meager campaign funds for an effective TV advertising blitz against Dowling in the final weeks. 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. Critical of the state legislature, Garrison was unanimously censured by it for "deliberately maligning all of the members". In 1965, running for reelection against Judge Malcolm O'Hara, Garrison won with 60 percent of the vote.
Kennedy assassination investigation As New Orleans D.A., in late 1966, Garrison began an investigation into the
assassination of President John F. Kennedy, after receiving several tips from
Jack Martin that a man named
David Ferrie may have been involved in the assassination. The result of Garrison's investigation was the
arrest and trial of New Orleans businessman
Clay Shaw in 1969, with Shaw being unanimously acquitted less than one hour after the case went to the jury. Garrison was able to
subpoena the
Zapruder film from
Life magazine. Thus, members of the American public – i.e., the jurors of the case – were shown the movie for the first time. Until the trial, the film rarely had been seen, and copies were made by assassination investigator Steve Jaffe, who was working with Garrison's office. In 2015, Garrison's lead investigator's daughter released his copy of the film, along with a number of his personal papers from the investigation. Garrison's key witness against Shaw was
Perry Russo, a 25-year-old insurance salesman from
Baton Rouge, Louisiana. At the trial, Russo testified that he had attended a party at anti-Castro activist
David Ferrie's apartment. At the party, Russo said that
Lee Harvey Oswald (whom Russo said was introduced to him as "Leon Oswald"), David Ferrie, and "
Clem Bertrand" (whom Russo identified in the courtroom as
Clay Shaw) had discussed killing President Kennedy. The conversation included plans for the "triangulation of crossfire" and alibis for the participants. An early version of Russo's testimony (as told in Assistant D.A. Andrew Sciambra's memo, before Russo was subjected to sodium pentothal and hypnosis) fails to mention an "assassination party" and says that Russo met Shaw on two occasions, neither of which occurred at the party. However, in his book
On the Trail of the Assassins, Garrison says that Russo had already discussed the party at Ferrie's apartment before any "truth serum" was administered. Scambria said that the party information was simply accidentally left off the notes of his encounter with Russo. Throughout his life, Russo reiterated the same account of being present for a party at Ferrie's house along with Mr. Bertrand, where the subject of Kennedy's potential assassination had come up. Garrison defended his conduct regarding witness testimony, stating: Before we introduced the testimony of our witnesses, we made them undergo independent verifying tests, including polygraph examination, truth serum and hypnosis. We thought this would be hailed as an unprecedented step in jurisprudence; instead, the press turned around and hinted that we had drugged our witnesses or given them posthypnotic suggestions to testify falsely. In May 1967 Garrison appeared on
ABC's
Issues and Answers program to discuss his investigation. Later in July Garrison was granted 30 minutes by
NBC to respond to their program criticizing his investigation. He used his time to dismiss the
Warren Report as a "fairy tale" and charged that "President Kennedy was assassinated by men who sought to obtain a radical change in our foreign policy, particularly in regard to Cuba". In January 1968, Garrison subpoenaed
Kerry Wendell Thornley – an acquaintance of Oswald's from their days in the military – to appear before a grand jury, questioning him about his relationship with Oswald and his knowledge of other figures that Garrison believed were connected to the assassination. Thornley sought a cancellation of this subpoena on which he had to appear before the Circuit Court. Theorizing that a plot to kill the president was masterminded out of New Orleans in conjunction with the
CIA, with cooperation from the Dallas police department and city government, Garrison allegedly tasked his former chief investigator, Pershing Gervais, to look into the possibility that General Cabell had stayed in the city's Fontainebleau Motel at the time of the assassination. The very same reasonings as to why he thought that President Kennedy was killed were espoused by Garrison in filmed television appearances that he would make leading up to his death, the year after Stone's release of his cinematic film
JFK, largely based on Garrison's pioneering role in the lone prosecution in the case of
President Kennedy's assassination. == Later career and death ==