William Greer was born in County Tyrone, Ireland, in 1910. His family emigrated to the United States. Greer worked as a farm labourer before moving to Boston where he became a chauffeur. After the bombing of Pearl Harbor Greer joined the US Navy. He was assigned to the presidential yacht in May 1944.
At the end of the Second World War Greer joined the U.S. Secret Service. He joined the staff of the White House in November, 1950. Over the next thirteen years he worked as a chauffeur for Harry S. Truman, Dwight Eisenhower, and John F. Kennedy.
On the 22nd November, 1963, Greer was assigned to drive the presidential car in the motorcade through Dallas. Several witnesses said that Greer stopped the car after the first shot was fired. This included Jean Hill, who was the closest witness to the car when Kennedy was hot: According to Hill "the motorcade came to almost a halt at the time the shots rang out". James Chaney (one of the four Presidential motorcyclists) - stated that the limousine "after the shooting, from the time the first shot rang out, the car stopped completely, pulled to the left and stopped." Mary Woodward, a journalist with the Dallas Morning News wrote: "Instead of speeding up the car, the car came to a halt... after the first shot".
Kenneth O'Donnell (special assistant to Kennedy), who was riding in the motorcade, later wrote: "If the Secret Service men in the front had reacted quicker to the first two shots at the President's car, if the driver had stepped on the gas before instead of after the fatal third shot was fired, would President Kennedy be alive today? He added "Greer had been remorseful all day, feeling that he could have saved President Kennedy's life by swerving the car or speeding suddenly after the first shots."
William Manchester claims that Greer told Jackie Kennedy at Parkland Hospital: "Oh, Mrs. Kennedy, oh my God, oh my God. I didn't mean to do it, I didn't hear, I should have swerved the car, I couldn't help it. Oh, Mrs. Kennedy, as soon as I saw it I swerved. If only I'd seen it in time!"
Senator Ralph Yarborough, who was riding with Lyndon B. Johnson, was highly critical of the actions of Greer: "When the noise of the shot was heard, the motorcade slowed to what seemed to me a complete stop... After the third shot was fired, but only after the third shot was fired, the cavalcade speeded up, gained speed rapidly, and roared away to the Parkland Hospital... The cars all stopped... 'I don't want to hurt anyone's feelings but for the protection of future Presidents, they (the Secret Service) should be trained to take off when a shot is fired."
It has been estimated that 59 witnesses and the Zapruder Film indicated that Greer stopped after the first shot was fired. However, when interviewed by the Warren Commission, Greer claimed: "I heard this noise. And I thought that is what it was. And then I heard it again. And I glanced over my shoulder. And I saw Governor Connally like he was starting to fall. Then I realized there was something wrong. I tramped on the accelerator, and at the same time Mr. Kellerman said to me, "Get out of here fast." And I cannot remember even the other shots or noises that was. I cannot quite remember any more. I did not see anything happen behind me any more, because I was occupied with getting away."
Greer also testified that he heard three shots and they all came from behind him. His testimony on Kennedy's head wound did suggest that a conspiracy had taken place. He claimed that when he got to Parkland Hospital he noticed Kennedy's "head was all shot, this whole part was all a matter of blood... it looked like that (his head) was all blown off." This contradicts the pictures of Kennedy's head that were published sometime after his death.
There is evidence that Greer also believed that John F. Kennedy had been a victim of a conspiracy. The daughter of Roy Kellerman, the Secret Agent in Kennedy's car, told Harold Weisberg in the 1970's that "I hope the day will come when these men (Kellerman and Greer) will be able to say what they've told their families".
William Greer died on 23rd February, 1985. His son, Richard Greer, was interviewed in 1991. When asked, "What did your father think of JFK," Richard did not respond the first time. When asked a second time, he responded: "Well, we're Methodists... and JFK was Catholic..."