We all know the scene in Oliver Stone's film JFK in which Guy Banister (Ed Asner) pistol-whips Jack Martin (Jack Lemon). Later on, Jack Martin goes on to tell Garrison the real reason it happened - he had witnessed a lot of strange things in the office. Here is the scene:

And, Jim Garrison, in his book On The Trail of the Assassins, tells the story of Jack Martin coming to his office, on the Monday after the assassination: (page 31)

"Well, when we came back to the office, Banister started bitching about one thing and then another. He was in a mean mood. Then all of a sudden, he accused me of going through his private files. No I never went through his private stuff ever - absolutely never. And that really ticked me off."

He hesitated for a long moment.

"Go on, Jack," I said gently.

"I guess I blew up," he continued, his face flushed with memories of injustice. "That's when I told him he'd better not talk to me like that. I told him I remembered the people I had seen around the office that summer. And that's when he hit me. Fast as a flash - pulled out that big Magnum and slammed me on the side of the head with it."

Of course, there is no internal Garrison memo about this conversation. The police report says something different. And here it is:

The police report only mentions unauthorized long distance telephone calls. Note that Delphine Roberts is listed as a witness. Why didn't they ask Delphine Roberts about this incident when she was interviewed? Perhaps because it really was a dispute about telephone charges.

Now, Garrison does claim that he mentioned the police report to Martin, who then asks "does a simple argument over phone bills sound like a believable explanation to you." And, of course, it doesn't. But, as David Reitzes argues, Banister had a history of such outbursts:

As the District Attorney himself told Life editor Richard Billings in December 1966, Banister was both a "violent man" and a "heavy drinker." According to Garrison's 1966 description, Banister was "probably insane before he died," an assessment borne out by others who knew him. Despite his former standing in the law enforcement community, Garrison advised Billings, Banister "went all the way down before he died" only a few months after the events of November 22nd.

Guy Banister's behavior was noted to be violent and erratic on numerous occasions during the late 1950s and early 1960s. In fact, in 1957 he lost his job as Assistant Superintendent of the New Orleans Police Department when, while drinking, he pulled a gun on a waiter in a French Quarter bar; and on March 31, 1964, he was arrested on a charge of aggravated assault after allegedly brandishing a pistol at three youths on a city bus

Reitzes quotes from Aaron Kohn's deposition before the HSCA on November 7, 1978. Here are the two pages from that deposition that talks about Guy Banister:

And there is some corroboration for the police report explanation of the pistol-whipping incident. Here is what Jack Martin told Harold Weisberg (these are notes of a conversation Washington Post reporter George Lardner had with Weisberg);

And Joseph Newbrough, a part-time detective for Banister, told the HSCA that Martin told him the argument was over long distance calls. Here is an excerpt from that report dated April 10, 1978. (HSCA Outside Contact Report of Joseph Newbrough, RIF# 180-10072-10214, courtesy of Jerry Shinley)

And, David Ferrie told the FBI about Martin's long distance phone calls. Might he have told Banister about them?

Francis Martello, the Lieutenant who wrote up the incident report, was interviewed by the HSCA on August 18, 1977: (HSCA Outside Contact report of Francis Martello, RIF# 180-10080-10206, courtesy of Jerry Shinley)

Jack Martin, a known fabricator, started embellishing the incident in an affidavit he wrote with David Lewis (another Garrison witness who had little credibility) on February 20, 1968:

Martin says that he went into Banister's private office and told him that he had "compiled, and kept records of all events we had either been involved in, exposed to, or heard about, bar nothing." Well, what ever happened to those records? Banister then gets mad about being double-crossed about a client - and that client was George Lincoln Rockwell. Martin then admits that is true.

Martin then says that "there had been no secret as far as anyone was concerned in regard to the fact that Banister, David William Ferrie, and Lee Harvey Oswald may have known, or been acquainted with one another." It's a strange statement - may have known? Did he not see them in the office?

Martin then basically accuses Banister of being involved in the JFK assassination, "We reminded him of this, together with the fact that he often mentioned, "Someday, somebody is going to poke a rifle out a window," when speaking of unpopular politicians at times."

Banister gets upset and talks about fighting, and Martin then says "Our reply was that we would most likely remain silent regarding him (Banister), but not Ferrie under any condition." Hold it, what happened to Oswald?

After the pistol-whipping, Martin runs off to the bar and says there are two witnesses, and perhaps "more witness may be available to this statement."

In the police report, Martin goes to the hospital, and then goes home and calls the police. No mention of going back to the bar.

Here is what Jack Martin told the HSCA on December 5, 1977 (RIF# 180-10080-10-208):

And, here is what Delphine Roberts told the HSCA about the pistol-whipping incident:

Roberts then thinks that Martin wanted the Oswald file, which contained "news clippings."

Cleary the pistol-whipping incident happened. It probably was about long-distance telephone calls. Jack Martin couldn't help himself - once Banister died, he was free to embellish all he wanted.

Update:

Here is an excerpt from a document from the Harold Weisberg Archive. He has a collection of notes from Hoke May - a reporter for the New Orleans States-Item. I can't tell if this is written by Weisberg from talking to May or by Hoke himself.

I have no idea if this is true, but if true, it would explain why everybody gave different reasons for the pistol-whipping.