It has been 55 years since US President John F Kennedy was assassinated. Countless conspiracy theories have, since then, surfaced in attempt to explain how the events really went down.
The most famous of these is the ‘grassy knoll’ theory.
Despite the arrest of Lee Harvey Oswald and subsequent analyses that showed JFK’s wounds lined up with the type of rifle Oswald owned, skeptics have proposed there was a second gunman standing on a hill to the front of the motorcade.
However, a new study could finally help put the debate to rest.
According to new calculations based on the video recordings of the assassination, the mysterious movement of the president’s head after being shot – a crucial detail in the grassy knoll theory – was the result of a recoil effect.
The videos further show that the fatal bullet impact was immediately followed by a forward head snap, adding further proof that JFK was shot from behind, as the official autopsy indicated.
According to the study’s author Dr. Nicholas Nalli, this initial forward movement can be seen in the famous footage captured by civilian Abraham Zapruder, who filmed the doomed Dallas motorcade on November 22, 1963 using an 8-mm home video camera, and inadvertently recorded the assassination.
The widespread grassy knoll theory centers around a number of ‘oddities’ in the initial findings, which showed that the president made a ‘back and to the left’ movement just after being shot.
According to proponents of the second gunman explanation, this suggests JFK was shot from the front by a person standing on a small hill on the northwest side of Dealey Plaza, otherwise known as the grassy knoll.
The new study published to the journal Heliyon, Nalli uses one-dimensional gunshot wound dynamics models to investigate these previously ‘glossed over’ events in greater detail.
The force calculations include known information from the crime scene, including bullet mass, speed, and diameter, as well as the camera shutter frequency and autopsy measurements and according to Nalli, the footage of the event supports the conclusion that Kennedy was shot from behind.
According to the analysis, the bullet deformed after colliding with the skull, transferring most of its kinetic energy to the head.
Some of this energy would have driven an impulse force immediately after, propelling the target forward about 2 inches (5 centimeters) over the course of one shutter cycle.
The rest of the kinetic energy would have gone into the soft tissue, Nalli writes.
A second backward acceleration seen in the President’s upper body after the shooting was likely a nervous system reaction to the ‘massive brain injury.’