Secrets of a Homicide: Acoustics

A New Way of Looking at the Acoustic Evidence

The conclusions of the HSCA acoustic experts hinge on a very basic assumption – a police motorcycle, with an open microphone, was transmitting the sound of the shots from four very specific locations at the time of the assassination. Those locations were predicted based on the close correlation of sound-impulses detected in the original 1963 police recordings, which acoustic experts believed were gunshot echo patterns, and actual gunshot echo patterns recorded during test firings conducted in Dealey Plaza in 1978.

It cannot be over emphasized that there are no audible gunshot sounds on the Dallas police recordings – a major flaw in the HSCA’s acoustic theory according to Dallas police radio dispatch supervisor James C. Bowles, who wrote in his critical 1979 report that police shootings have been recorded in other instances and the gunshots are easily heard.

In order for the acoustic analysis to be correct and valid, a police motorcycle must actually exist at the four specific locations and times predicted by the acoustic analysis. Consequently, the assumed position of the motorcycle is at the heart of the acoustic analysis. All of the conclusions about the timing and source of the shots, as set forth by Bolt, Beranek and Newman, Inc. (BBN); Mark Weiss and Ernest Aschkenasy of Queens College (WA); and later by Donald B. Thomas, particularly, that one shot was fired from the grassy knoll and therefore there was a conspiracy to assassinate President Kennedy, stem from that assumption. If there is no motorcycle at the location and times predicted by their analysis, their conclusions are, by default, invalid.

In an effort to resolve the continuing debate over the validity of the acoustic evidence in the Kennedy assassination in a manner that would be obvious even to those who can’t fathom the CBA report or other continuing acoustic studies, a re-examination of the photographic evidence was undertaken to determine whether or not H.B. McLain’s motorcycle (or any police motorcycle for that matter) was in the position predicted by the HSCA acoustic experts.

The study involved using a computer model of Dealey Plaza to geometrically synchronize nine amateur films that captured portions of the motorcade’s journey through the plaza.

The result, which was presented to ABC News in 2003 and is detailed here for the first time, is a definitive, reconstructed photographic record that reveals the precise location of the pertinent motorcade vehicles at the time of the shooting. This conclusive record demonstrates that no police motorcycles – including, Officer H.B. McLain’s – were near the area designated by the HSCA’s acoustic experts, and consequently, the committee’s acoustic evidence of a conspiracy in the Kennedy assassination is invalid.

A Photographic Approach

Nine amateur 8mm films documenting the presidential motorcade’s journey through Dealey Plaza were chosen for the photographic analysis portion of this project. They are the films of:

  1. Robert Hughes
  2. Marie Muchmore
  3. Elsie Dorman
  4. Orville Nix
  5. Tina Towner
  6. F.M. Mark Bell
  7. John Martin, Jr.
  8. Charles Bronson
  9. Abraham Zapruder

The most famous of these is Abraham Zapruder, who is the only photographer to capture the entire shooting sequence.

The nine other amateur photographers, each armed with an 8mm film camera, captured portions of the 32-second period proceeding the shooting, the shooting itself, and some of the events that followed. Many of the sequences overlap and all are very brief - less than five seconds in length.

Because these multiple, fragmentary amateur films collectively capture a single event, it is possible to synchronize all of these films together to reconstruct a continuous record of the original event.

Two films in particular are of prime importance with regard to the acoustic question - the Hughes film and the Zapruder film.

The Hughes film depicts motorcycle officer H.B. McLain, who the HSCA claimed was the motorcycle officer with the open microphone. The Zapruder film documents the shooting sequence.

By determining the relationship between these two films, it is possible to establish McLain’s position during the shooting sequence, and therefore, determine whether McLain was, as the HSCA claimed, near the corner of Elm and Houston Streets at the time of the first shot, or whether any other motorcycles were there; and hence, establish the validity of the acoustic evidence.

Synchronization Issues

Unlike professional motion picture cameras, the amateur 8mm cameras used to record the Kennedy motorcade were not electronically synchronized nor were they motor-driven. Each of the nine amateur cameras in this study was spring wound resulting in frame rates that could vary by 3% depending on how tightly the operator had wound the spring before filming, how long the camera was in continuous operation, and several other factors, all of which contributed to the camera’s functionality. Consequently, the film footage these cameras produced will never exactly match each other frame-for-frame.

Even when two spring wound cameras are running simultaneously, one camera will always be exposing frames a millisecond before or after its counterpart. For purposes of this analysis, those variable milliseconds will make little or no difference.

In synchronizing the amateur films for this project, an error ratio of plus-or-minus (+/-) one frame (approximately one tenth of a second) was deemed acceptable, and therefore considered synchronous.

In order to achieve synchronicity between amateur cameras running at variable frame rates it was necessary to first determine each camera’s average operational frame rate.

Establishing a Clock

Of all the amateur films of the Kennedy assassination, the film made by Abraham Zapruder has received the most scrutiny. In 1964, the FBI laboratory conducted a detailed examination of Zapruder’s 8mm camera, a Bell & Howell Zoomatic Director Series, Model 414PD. [Exhibit 1]

The FBI determined through testing that Zapruder’s camera ran for 60 seconds when fully wound and that the “normal run speed” was an average of 18.3 frames-per-second (fps). The FBI tests showed that this average speed varied by approximately 3%, or about 1 frame. [101]

The FBI also examined the amateur cameras used by Orville O. Nix, Sr., and Mrs. Marie Muchmore. In early 1964, the FBI reported that the Keystone Auto-Zoom Model K-810 8mm movie camera owned by Orville Nix and the Keystone K-7 zoom lens 8mm movie camera used by Marie Muchmore both had an average running speed of 18.5 frames/second. [102]

While the FBI did examine the film made by Robert Hughes, they did not conduct any tests on the Hughes camera to determine its average running speed, nor were any other amateur film cameras studied to determine their running speed.

Because of the unique tests conducted on Zapruder’s 8mm Bell & Howell camera, and the fact that the Zapruder film is the only film to show the entire shooting sequence, the Zapruder film was chosen as the primary clock for this project.

The running speeds of all other amateur cameras in this study are therefore considered relative to Zapruder’s average camera speed of 18.3 frames-per-second.

Film Preparation

Each of the nine amateur films used in this analysis was prepared from original sources. [103]

The original 8mm film footage produced by the nine photographers had been transferred to professional video tape by various sources. The speed at which the original films were transferred to video tape was established by “eyeballing” the film footage to see “what looked most natural.” This subjective approach resulted in two potential problems.

First, the transfer rates that were ultimately used had no relationship to the actual speed of the recording camera. These transfer rates varied between 16 and 20.2 frames-per-second (fps). Second, the conversion of film rates of 16 - 20 fps to a standard NTSC video rate of 29.97 fps resulted in redundant (i.e., multiple copies of a single frame) and blended frames (i.e., two adjacent film frames blended to produce a third “non-existent” frame). Redundant and blended frames are artifacts of all film to video transfers and are not peculiar to amateur films of the Kennedy assassination.

Before beginning an analysis of these films for this project, new digital masters with a 1:1 relationship with their original film counterparts were created for all nine amateur films under discussion. This was accomplished by transferring the video tape masters to computer hard drives, converting the video sequences to numbered frame sequences, eliminating all redundant and blended frames, and renumbering the sequences. [Exhibit 2]

The renumbering process followed the numbering standard used by the Warren Commission to identify individual frames of the Zapruder film (i.e., the first frame depicting scenes shot in Dealey Plaza was number 001.) All of the frame numbers referred to in this document, except where otherwise noted, reflect this renumbering process.

Determining Frame Rates

In order to establish synchronicity between all of the amateur films in this project, it was necessary to determine the average frame rate of each untested amateur camera relative to the known average frame rate of Zapruder’s camera. This average should fall within the normal run-time range (16-24 fps) that amateur cameras of the era were capable of operating at.

Two methods were used to determine those average frame rates:

  1. Visual reference
  2. Computer assisted geometric reference

The method of visual reference was as simple as comparing each frame of one amateur film with the frames of a second amateur film and looking for instances where the same action was depicted in both. Enlargements, stabilized sequences, and mosaic enhancements were created in software programs like Abode Photoshop for analysis. Since several of the films under study (particularly Hughes, Dorman, and Towner) were created during the same time period, there were numerous points of reference which became the basis for achieving synchronization.

These visual reference points were aided and supported by geometric reference points established using a computer model of Dealey Plaza created for this project with NewTek’s
LightWave 3D. [Exhibit 3]

The model was based on survey maps prepared for the City of Dallas and the 1978 House Select Committee on Assassinations. More than 500 personal photographs and measurements, gathered during multiple trips to Dallas, Texas, were utilized in the construction and placement of all fixed structures — including the Records, Criminal Court, and Dal-Tex Buildings. The model of the Texas School Book Depository was created from blueprints prepared for the 1978 restoration project. A multitude of contemporary photographs and films were studied in order to ensure that the model matched Dealey Plaza circa 1963. Contours of the surrounding earthscape were plotted using a grid of markers, which were physically placed in Dealey Plaza and photographed from multiple angles. These photographs were then imported into software which extracted three-dimensional data from the images to create a dimensional model of the landscape.

The position of each of the amateur photographers on November 22, 1963, was determined by placing a virtual camera into the computer model and matching the virtual camera’s view of the computer model of Dealey Plaza with the actual view of Dealey Plaza as captured on film. [See, Triangulation, for a complete description.)

Once the photographers positions had been established, lines-of-sight were plotted between each virtual camera and fixed points in the computer model (i.e., corners of buildings, curb lines, window frames, etc.). These lines-of-sight became the basis for establishing geometric relationships between the individual photographers and their surroundings. By comparing the visual record (as captured on film) with the geometric relationship between the photographers and their surroundings, it was possible to establish:

  1. Numerous synchronization points between each of the amateur films, and
  2. The average frame rate of each camera, relative to Zapruder’s camera.

The resulting synchronization of these amateur films establishes a single, continuous timeline which reveals the precise speed, path and position of each of the pertinent motorcade vehicles at the time the assassination shots were fired, including Officer H.B. McLain’s motorcycle.



  1. The FBI lab reported on December 20, 1963, that the “normal run speed” of Zapruder’s camera was 18.3 frames per second (fps). At the end of January 1964, the Commission requested that the FBI check the variation in the speed of the camera when the spring was fully wound and when it had run down. Subsequent tests (at ten second intervals) showed that during the first ten seconds the camera ran at an average speed of 18.0 to 18.1 fps, increased to 18.3 to 18.5 fps during the next 20 seconds, decreased to 18.1 fps for ten seconds, and finished the final 20 seconds at a speed of 17.6 to 17.9 fps. Since the Zapruder film was exposed during the first half of the camera’s run, the FBI ignored the test figures recorded during the final 20 seconds. The remaining figures showed an average speed of 18.3 fps. [RETURN]
  2. Trask, Richard B., Pictures of the Pain, Yeoman Press, 1994, pp.190, 201, 206 [RETURN]
  3. With the exception of the F.M. “Mark” Bell, and John Martin, Jr., films, which used the best available sources. [RETURN]

Secrets of a Homicide: JFK Assassination © 1995-2011 Dale K. Myers. All Rights Reserved.
Published by Oak Cliff Press, Inc., P.O. Box 608, Milford, MI 48381-0608