No, I don't require them to be perfect, Leslie, but I think Garrison made a fatal mistake charging Shaw with being part of the plot to kill JFK. No one made him do that. I'm sure he would have preferred Dave Ferrie or Guy Banister, but they were dead. He should have just continued his investigation and not made any charges he couldn't prove. He also made a lot of reckless and unfounded statements in early press interviews.
Feb 24 1967: Garrison announced to the press, "I have positively solved the assassination of President John F. Kennedy. My staff and I solved the case weeks ago. I wouldn't say this if I didn't have evidence beyond the shadow of a doubt. We know the key individuals, the cities involved and how it was done. There were several plots, but that's more than I wanted to say. Ferrie might not be the last suicide in the case. The only way they are going to get away from us is to kill themselves....The key to the whole case is through the looking glass. Black is white and white is black. I don't want to be cryptic, but that's the way it is....There will be arrests, charges and convictions. This is no Mickey Mouse investigation."
Maybe this was just an enormous bluff designed to rattle the entire government. But it looks reckless to me. He veered back and forth between making very perceptive and smart comments, and then making wild charges that he couldn't support.
May 21 1967 In an interview on WWL-TV, New Orleans, Garrison claimed that the CIA knew the names of the other assassins, but "we can't find out [their names] with the CIA keeping its vaults locked...If the director of the CIA and the top officials of the CIA were in the jurisdiction of Louisiana, I would charge them without hesitation." That day he also stated that the CIA knew "the name of every man involved and the name of the individuals who pulled the triggers" (NY Times 5/23)
May 28 1967 On "Issues and Answers," (ABC-TV) Garrison said,
"Of course the Central Intelligence Agency had no role in the planning or intending the assassination of President Kennedy. I think that would be a ridiculous position for anyone to take." 
Sep 24 1967 Garrison charged that RFK was "without any question of a doubt...interferring with the investigation of the murder of his brother" and was making "a real effort to stop it." ("Page One," WABC-TV, New York)
Jan 26 1968 Paul Rothermel, a former FBI agent hired by H.L. Hunt as an investigator, wrote a memo to Hunt: "The source of the information reports that Garrison is convinced that the assassination was carried out by Gen. Edwin Walker with the financial support and backing of Herman and George Brown of Houston and H.L. Hunt of Dallas. He said that Garrison is a heavy drinker and lives extravagantly...We have extended our cooperation to Garrison in his probe hoping to help guide his investigation. I think everyone would like the assassination solved, and certainly there is no member of the Hunt family or organization who has the least thing to hide. In spite of the above, there have been persistent stories to the effect that Garrison either suspects or is antagonistic toward the Hunts. We have no proof that this is the case. It is reported that Garrison is a most vindictive left winger, that he is bisexual and a clever blackmailer. Garrison understands public opinion, and can without introducing evidence of proof, harass, intimidate, and smear whomever he wishes."