If you’ve spent any time in the darker corners of the internet—or watched a grainy, fifth-generation VHS copy of the Zapruder film back in the 90s—you’ve probably heard it. The whisper that’s so wild it almost feels like a dare. Some people honestly believe the man behind the wheel of the presidential limousine, Secret Service agent William Greer, was the one who pulled the trigger.
It sounds like a plot from a low-budget thriller. A man tasked with protecting the President of the United States suddenly turns around and executes him in broad daylight.
Most people who stumble onto this theory feel a weird mix of shock and "wait, let me look at that again." But when you actually dig into the mechanics of the day, the ballistics, and the history of how this rumor started, the whole thing falls apart faster than a cheap suit. Let's get into what really happened with the theory that did the driver kill JFK.
Where the "driver did it" theory actually came from
Conspiracies don't just pop out of thin air. They usually start with a visual "glitch." In this case, the glitch is a specific moment in the Zapruder film.
Around frame 313—the moment of the fatal head shot—William Greer, the driver, reacts. He turns his head back to see what’s going on. In low-quality, blurry copies of the film, there’s a flash of light. To a casual or perhaps overly suspicious observer, it looks like he’s holding a nickel-plated revolver.
It’s an optical illusion. Plain and simple.
What you're actually seeing is the sun reflecting off the top of Secret Service agent Roy Kellerman’s head, or sometimes the sun reflecting off the chrome trim of the car. Kellerman was sitting in the front passenger seat. He had a very distinct, slicked-back hairstyle that, when hit by the harsh Texas sun, creates a bright white glare on grainy 8mm film.
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Basically, people were looking at a blurry smudge and seeing a gun.
The William Greer theory explained (simply)
Milton William Cooper, a former radio personality and author of Behold a Pale Horse, was one of the loudest voices pushing this. He didn't just stop at a gun, though. He claimed Greer used a "gas pressure device" developed by aliens. Yeah. It got that weird.
Cooper's argument hinged on the idea that the Zapruder film had been edited to hide the driver’s arm movement. He told his followers that if you looked at "the real film," you’d see Greer reach across his body and fire.
But here’s the problem with that logic.
There were dozens of witnesses standing feet away from the car. Mary Moorman was taking a photo just yards away. Jean Hill was right there. Not a single person—not one—reported seeing the driver turn around with a weapon. They saw him turn to look, sure. But they didn't see him shoot.
If Greer had pulled a gun, the people standing on the grass would have been staring right down the barrel.
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Why the ballistics prove it's impossible
If you're asking did the driver kill JFK, you have to look at the wounds. The medical evidence from both the Warren Commission and the later House Select Committee on Assassinations (HSCA) is pretty clear about the direction of the shots.
- Entry and Exit: The fatal wound to Kennedy's head involved an entry in the rear and an exit in the front/side.
- The Angle: If Greer had shot Kennedy from the driver’s seat, the bullet would have entered the front of Kennedy’s head and traveled toward the back of the car.
- Physics: The massive "blowout" wound was on the right side and front of Kennedy's skull.
If the driver were the shooter, he would have had to perform a physical miracle. He'd have to turn 180 degrees, aim a weapon over his right shoulder while the car was moving, and hit a target behind him in a way that made the bullet look like it came from the rear. It’s physically nonsensical.
Also, we have to talk about the "jet effect." One reason people think a shot came from the front is because Kennedy’s head moves "back and to the left" in the Zapruder film. This was a huge point in Oliver Stone’s movie JFK. However, forensic experts like Larry Sturdivant have explained that this is a common reaction to a high-velocity impact from the rear. The brain matter exiting the front creates a recoil effect, pushing the head backward.
The real tragedy of William Greer
The irony of the "driver did it" theory is that William Greer did feel immense guilt. But it wasn't because he killed the President. It was because he didn't accelerate fast enough.
Greer was a 54-year-old agent from Ireland who had been with the Service for decades. He was a "company man." On that day in Dallas, when the first shot rang out, he didn't immediately floor it. He slowed down. He even momentarily tapped the brakes to look back and see what the noise was.
In the Secret Service, that’s the ultimate sin. You’re supposed to "get off the X"—the kill zone—immediately.
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Jackie Kennedy was famously bitter toward Greer for years. She reportedly told friends that the driver should have done more. Greer himself was haunted by it until his death in 1985. His son, Richard Greer, later spoke about how the accusations of being a murderer devastated his father.
"He had a lot of guilt about what happened," his son once mentioned, but the idea that he was a conspirator was something the family found offensive and absurd.
What we know for sure
So, did the driver kill JFK? No.
There is zero physical evidence, zero witness testimony, and zero forensic logic to support it. It’s a theory born of bad film quality and a desire to find a "hidden" truth in a story that is already incredibly complicated.
The real story of the JFK assassination is messy enough without adding alien gas guns or secret service traitors. You’ve got Lee Harvey Oswald, the Grassy Knoll theories, the CIA’s shady history, and the mob’s beef with RFK. Those are the areas where real historians and researchers spend their time because there's actually something to debate there.
The driver theory is mostly a relic of pre-digital age "research" where people saw what they wanted to see in the shadows of a grainy film.
Actionable steps for the curious
If you want to really understand why this theory is debunked, don't just take a blogger's word for it. You can actually do the legwork yourself:
- Watch the high-definition Zapruder scans: Look for the 1998 MPI Home Video release or the more recent digital restorations. In high-def, the "gun" clearly becomes a reflection of sunlight on Roy Kellerman's hair.
- Read the Warren Commission Testimony: Check out Volume II, page 112. That’s William Greer’s actual testimony. You can read his own words about why he turned around and what he was thinking in those seconds.
- Check out the 3D Forensic Reconstructions: Modern forensic teams have used LIDAR and 3D modeling to recreate Dealey Plaza. These models show that a shot from the driver’s position is blocked by the seats and the other passengers.
The mystery of Dallas will likely never be "solved" to everyone’s satisfaction. But we can at least cross the driver off the list. He was just a man who had a very bad day at work—and spent the rest of his life wishing he’d driven a little bit faster.