Secrets of a Homicide: Summary of Conclusions

3. A trajectory analysis of JFK's inshoot/outshoot head
wounds shows an inconsistency with the HSCA
trajectory conclusions.


The Zapruder film shows JFK receiving his head wound at frame 313. Using medical data from the House Select Committee on Assassination's (HSCA) Forensic Pathology Panel and Zapruder frame 312 (JFK's last known position before impact), a trajectory was plotted to determine the source of the shot.

The HSCA Forensic Pathology Panel located the entrance wound on the back of the head about 3.9 inches above the external occipital protuberance, and 0.7 inches to the right of the midline. An exit wound was located near the right temple 4.3 inches in front of, and 0.4 inches below the entrance wound, about 2.2 inches right of the midline. These points were located on a computer model representing JFK's skull. The two points were connected with a straight line and projected rearward 200 feet to represent the trajectory of a missile passing through these two points. The trajectory track was then applied to the recreation at the equivalent of Zapruder frame 312.
JFK entrance/exit wounds - rear/side view

JFK inshoot/outshoot wound trajectory The results show a trajectory track (blue line) that intersects the western face of the Dal-Tex Building, 33.5 feet north of the south face, and 124.6 feet above the roofline. This finding is at odds with the HSCA Photographic Panel which calculated a trajectory that intersected the Texas School Book Depository at a point 11 feet west of the southeast corner of the building and 15 feet above the sixth floor window sill. (6HSCA41) The discrepancy is due to a calibration photograph used by the HSCA to position JFK's head at Zapruder frame 312. A comparison of this photo with Z312 and the corresponding computer frame reveals apparent rotational differences.

During HSCA testimony, it was noted that JFK's head had a "much more severe pitch" in Z312 than seen in the calibration photo. Thomas Canning, a NASA staff engineer, explained that the "interpretation of [JFK's] features is certainly one of the major sources of potential error," which was calculated to be about 2 degrees at Z312. (2HSCA193)
Computer recreation (left), Z312 (center), HSCA calibration photo (right)

Canning, however, did not specifically address the issue of the apparent pitch differences between Z312 and the calibration photograph.

Canning's study found JFK was "turned partially away from Zapruder - approximately 25 degrees past the 90 degree, or profile, direction. His head was tilted away from Zapruder by about 15 degrees, and he appeared to be nodding forward by about 11 degrees (clockwise, as viewed by Zapruder)." (6HSCA38)

By contrast, the computer recreation found the orientation of JFK's head at Zapruder frame 312 to be turned away from Zapruder by 25.7 degrees, tilted to the left 18.1 degrees, and nodding forward 27.1 degrees - relative to Zapruder's view.

The computer calculations, which contain a 2 degree margin of error, are comparable with the HSCA findings - with the exception of the pitch (forward nodding) of JFK's head. The computer recreation shows the angle to be about 16 degrees steeper than Canning calculated. Using Canning's figures to position JFK's head in the computer recreation reveals an obvious misalignment with the Zapruder film. For this reason, the computer recreation is believed to represent a closer match to the actual orientation of JFK's head, than the position proposed by the HSCA Photographic Panel.

Since (a) the position of JFK's head used in the computer recreation closely matches Zapruder frame 312 (within a 2 degree margin of error), and (b) a trajectory line based on the HSCA's outshoot wound tracks to an impossible firing source located 124 feet above the roofline of the Dal-Tex Building, it is concluded that the outshoot wound used by the HSCA to calculate a trajectory path was not the result of a straight line trajectory (i.e., the bullet was deflected after making contact with the skull).

The HSCA Forensic Pathology Panel did note evidence of a deflection: "The small missile fragment present at the margin of the entrance wound was probably a portion of the missile jacket and indicates that the skull might have slightly deflected the course of the missile and its fragments through the head." (7HSCA176)

Although they believed the bullet that struck the president's head exited as one piece, the HSCA Forensic Panel conceded that evidence of an additional exit defect might exist on one of the bone fragments missing from the president's skull: "Within one or several of these fragments, there might be an additional exit defect if the principal missile had divided into two major fragments within the skull, although in the experience of the members, the estimated size of the principal exit defect is consistent with the size of a single exiting missile representing the mass of the two major fragments recovered outside the body." (7HSCA128)

These two fragments were found in the presidential limousine - a nose portion of a bullet found on the right side of the front seat, and a base portion of a bullet found on the floor next to the right front seat. Whether the bullet striking the president's head broke in two before exiting or upon impact with the interior of the limousine is therefore a matter of conjecture.

Since the exit wound may have been one of several, and because of the existence of evidence suggesting deflection, a straight-line trajectory is impossible to establish with any degree of reliability. Although it can be concluded that the head shot was fired from the rear, the massive defect in the right front skull precludes the use of a trajectory cone to narrow the field of sources, since the size of the error cone would encompass nearly the entire area behind the limousine.

JFK Hypothetical trajectory - side/top view Considering that this computer study shows that at least one shot was fired from the Texas School Book Depository (see conclusion #2), a hypothetical trajectory was plotted between the sniper's nest window and the entrance wound on the back of the president's head to test whether such a shot fit the pattern of evidence.

The hypothetical trajectory path (red line) was extended forward without deflection and compared with the path plotted by the HSCA (blue line) to determine the amount of deflection necessary to match the known medical and physical evidence.

The following results were obtained:

A bullet fired from the sixth floor sniper's nest window, entering the skull at the point designated by the HSCA and exiting without deflection would exit within the large defect area described in the autopsy report.

A bullet would have to deflect 20 degrees downward, and 4 degrees right to exit at the HSCA's outshoot point.

A 16 degree deflection upward would cause the bullet to intersect the windshield in front of the driver, where a crack in the windshield was discovered.

JFK Hypothetical trajectory - side/top view
In conclusion, a headshot trajectory cannot be calculated from the available evidence, due to (a) the possibility that the bullet fragmented, creating more than one exit wound, and (b) the likelihood that the course of the bullet changed after striking the skull. A hypothetical trajectory plotted from the Texas School Book Depository sniper's nest window - a known firing source - to the entrance wound on the back of the president's head shows a number of angles that correspond favorably with damage to the interior of the limousine. However, the theoretical nature of this trajectory prevents any firm conclusion from being drawn from the computer recreation alone.

It should be noted, however, that firearms evidence conclusively established that bullet fragments recovered from the President's brain and bullet fragments recovered from the floor of the limousine came from the same bullet - a bullet fired from the Mannlicher-Carcano rifle found on the sixth floor of the Texas School Book Depository.

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Secrets of a Homicide: JFK Assassination © 1995-2008 Dale K. Myers. All Rights Reserved.
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