The following, from AMERICAN GROTESQUE (pp. 163-164), marks what
had to have been the turning point for William Gurvich.  The
narrator is James Phelan, to whom Garrison had given the Sciambra
Memo and the transcript of the hypnosis session (apparently without
reading them).

When Phelan discovered that Garrison was actually willing to *use*
Russo's testimony, his first reaction was to go to Garrison,
apparently on the assumption that Garrison was acting in good
faith, and didn't realize the fraudulent nature of Russo's
testimony.

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     Then I attend the preliminary hearing and I sit there
and listen to Russo tell this marvelously detailed story
about the party [the "assassination party"] that he'd not
mentioned when he first appeared as a witness. The
following day I called Garrison at his home and told him
there was something deeply troubling me and he said, "Come
out here and tell me about it." I went out to his house and
he was there with his wife and children and shortly after
I got out there Bill Gurvich and his wife came out and I
told Garrison that--I said, "How come Perry Russo told two
different stories?  How come when he first appeared he did
not identify Shaw as Bertrand, he did not say Shaw knew
Oswald, and he said nothing at all about an assassination
plot at any party."  His mouth kind of dropped open and he
said, "He didn't?"  At that point I realized Garrison had
not read the memos he'd given me. He said, "Well, I'll have
to get Moo-Moo [Sciambra] out here and explain it."

     Sciambra comes out there.  They shoo the women out of
the room and sat down and Garrison said, "Okay, tell him
your problem." I did, and Sciambra came back at me real
hard and said, "Mister, you don't know what the shit you're
talking about!" I said, "Look, I've got some bad news for
you, Moo." I said, "I've read your memo, I've got a copy of
your memorandum, and I've read it six, seven, eight times.
I can almost recite it from memory and there ain't nothing
in there about the assassination plot. I'll tell you how
sure I am." I said, "I'll make a deal with you. If that
memo isn't the way I've described it, I'll resign from the
Saturday Evening Post tomorrow if it is the way I described
it, you resign from the D.A.'s office tomorrow.  We'll
shake hands and then read the memo and tomorrow one of us
is going to be out of work."  At that point he immediately
backed off, like that [Phelan snapped his fingers]. I said,
"Jim, get a copy of the memo" because I'd left mine in the
safe down at the hotel so Garrison is rummaging around in
the drawer alongside his desk trying to find the memo.

     Then Sciambra changed his story. Now he says, Well, he
wrote the memo in a big hurry and he said maybe he forgot
to put in about the assassination plot.  And I told him to
come down off the wall I said, "Come on, now, you found a
witness to the crime of the century and you come down and
write a 3,500-word memo and leave the crime out of it--put
in all this other chicken-shit stuff--but you leave the
crime out!" I said, "Nobody can be that stupid. . . .
Besides, this hypnosis transcript shows how the thing was
pulled out of him." So we ding-donged it back and forth and
Gurvich sat there and never said a word, over in the
corner. I said, "You know the thing that really hangs me up
is that you said Russo said he saw the man twice and named
the two times, once on the Nashville Wharf and once in a
car with David Ferrie.  So if he told you about the party
you not only had to forget to leave out about the party but
you also had to change the number of times to conform with
what you told here, and that won't work." Sciambra was
pretty hostile. We broke up and nobody was very friendly
with anybody else. I said, "I'll call a cab and go back."
And Gurvich says, "No, I'm going back to town, I'll drive
you back."

     I get in the car with Gurvich, who was his chief
investigator, and this thing made a terrible impact on him.
He said, "Man, you have just blown up the only witness
we've got." He said, "I'll never forget Sciambra sitting
there lying to you." He said, "This little son of a bitch,
this was his little magnum opus and he sits there telling
you he had a half-dozen other things to do.  This was the
one big thing that this little S.O.B. did and he sat there
saying, 'Maybe I forgot'" Gurvich said, "Man, he worked
that memo over and polished it and repolished it." Gurvich
was terribly upset.