James Phelan was one of the first journalists that Jim Garrison talked to about his investigation. They both flew to Las Vegas and Garrison spelled out his story. He gave Phelan two memos regarding Perry Russo, his star witness against Clay Shaw. Phelan noticed that the memo written by Assistant District Attorney Andrew Sciambra, based upon his initial interviews in Baton Rouge, did not contain the story of the party at David Ferrie's where the discussion of the assassination took place.
Phelan photocopied the memos and confronted Garrison back in New Orleans. Garrison called over Sciambra who explained that he 'forgot' to put in the party.
Here is a memo written by James Phelan on the discrepancies and contradictions in Perry Russo's story.
There you have it. Perry Russo was Garrison's star witness - and it was on the basis of his recovered memory that Clay Shaw was arrested on March 1, 1967.