Ken O'Donnell denied the allegations that he changed his testimony under pressure from anyone. He told the Chicago Tribune in an interview that they were "an absolute, outright lie." And Dave Powers, also quoted by O'Neill, denied the story as well.
I'll be lazy here and quote Wikipedia on this:
"In their memoir of Kennedy, Johnny, We Hardly Knew Ye, both O'Donnell and David Powers reported hearing only three shots and did not offer any speculation as to their origin.[12] According to a June 15, 1975 report in the Chicago Tribune, an unnamed "Central Intelligence Agency liaison man" told Congressmen that O'Donnell and David Powers had initially told assassination investigators that the shots that struck Kennedy came from a location other than the Texas School Book Depository, but that the two men were convinced, reportedly by FBI Director J. Edgar Hoover or his main aides, to alter their accounts to the Warren Commission to avoid the possibility of revealing the CIA's plots to kill Fidel Castro which might result in an international incident.[12] During a telephone interview, O'Donnell said he testified truthfully and called the allegations "an absolute, outright lie."[12]
In his 1987 autobiography Man of the House, former House Speaker Tip O'Neill wrote that he had dinner with O'Donnell and Powers in 1968, and that both men indicated that two shots were fired from behind the fence on the grassy knoll at Dealey Plaza.[13] According to O'Neill, he pointed out to O'Donnell that he gave different information to the Warren Commission, and O'Donnell replied: "I told the FBI what I had heard, but they said it couldn't have happened that way and that I must have been imagining things. So I testified the way they wanted me to. I just didn't want to stir up any more pain and trouble for the family."[13] However, Dave Powers denied such conversation and claim occurred and criticized his autobiography.[14]
Again, O'Neill's allegations were denied by both men.
See here: https://news.google.com/newspapers?id=lQhIAAAAIBAJ&sjid=TQANAAAAIBAJ&pg=1934%2C3948488&hl=en
This is another example of how Michael Griffith uncritically accepts information that supports his pre-determined conspiracy view. And it doesn't matter whether it contradicts other claims he believes. Remember again he believes in the acoustics evidence that concluded three shots were fired from the TSBD and another shot came from behind the fence. But he quotes allegations that O'Donnell said the shots came from in front of the limo. That is, of course, completely at odds with the acoustics analysis. But he doesn't care.
Uh-huh, to believe Powers, you'd have to believe that O'Neill must have inexplicably fabricated the conversation.
I don't buy Powers' denial. I can't imagine why someone like Tip O'Neill, a close friend of the Kennedys and a sober and serious elected official who was not a WC skeptic at the time, would have lied about this.
Did it ever occur to you that Powers didn't realize how much publicity O'Neill's account would generate and didn't want to spark controversy by acknowledging that he had in fact confirmed O'Neill's account at the dinner and later when O'Neill checked with him?
So do you think O'Neill also lied about contacting Powers to confirm his account before deciding to include the account in his memoir? Why would he have done such a thing?
I find it much more plausible to believe that Powers gave a false denial because he was surprised by the attention sparked by O'Neill's account and because he did not want to cause further controversy by acknowledging that O'Neill's account was correct.