The Third Shooter

[Anthony Mugan]

Hello

I was wondering if I could begin a thread to discuss some preliminary thoughts around the implications of the acoustic evidence for the possible location of a third shooter in Dealey Plaza?  I did originally plan to write a paper on this but in practice I'd need to learn how to be a cartographer to get all the diagrams in to do it to the standard I'd like, which in reality just won't happen so, after mentioning this briefly elsewhere (on Larry Hancock’s blog, as a comment) I’m taking advice to present it here for scrutiny and for others to take it forward or falsify it.

 

The Third Shooter: A Preliminary Discussion:

 

Introduction:

When reading Dr Donald Thomas' 'Hear no Evil'¹ it struck me it might be possible to extract a little more information from the second of the five shots recorded on the acoustic evidence (in this discussion my starting point is the model of the physical events presented by Thomas - so that is itself a key set of assumptions).

 

In Thomas' model shot 4 correlates to the fatal headshot at Z312-3. It is reasonable to assume three shots were fired from the 'sniper's nest' in the TSBD from the number of cartridge cases recovered at the scene and the strong statistical correlation in the HSCA test shots of a number of the shots to that test location. The time gaps between shots create a problem, however, in that shot 2 is 1.65 seconds after shot 1 and shot 3 follows on 1.1 seconds later. These intervals are too close together for all three to have come from the same bolt action rifle in an aimed manner. Rather illogically, the HSCA discounted shot 3 as a false positive and in the process introduced problems with their proposed timings in relation to the Zapruder film, as they were trying to fit the data to a conclusion that the fatal headshot came from behind. More logically,  the data implies (together with the correlation to that location in the acoustic model)  that the shots from the SE corner window of the 6^th floor ( the ‘snipers nest) were shots 1, 3 and 5 with shot 3 impacting on JFK and the Governor around Z224. That leaves shot 2 which is too close in time to shots 1 and 3 to have come from the same bolt action rifle. That shot statistically correlated to the test location used in the TSBD (although this does not rule out an actual point of origin in the general vicinity) and, for reasons discussed below, the Grassy Knoll can be ruled out as the point of origin for that shot. In other words, there was a third shooter.

 

What struck me is that the HSCA acoustic analysis² notes that there is no shockwave recorded on this shot and that is consistent (assuming the modelling of the location of Officer McClain's bike is approximately correct) with a shot from the TSBD. That is correct even after adjusting the location of McClain's bike to the better correlation with the Zapruder film developed by Thomas¹, who notes that the absence of a shockwave rules out a location for this shot on the Grassy Knoll, which is also correct. My suggestion is that we can go slightly further in drawing information about the possible locations for this third shooter from the absence of a shockwave.

 

Background on the significance of the absence of a shockwave:

 

Rifle bullets are typically supersonic. Their acoustic signature therefore contains two components.

1. The muzzle blast extends out in all directions from the muzzle of the rifle at the speed of sound.

2. A shockwave is generated by the bullet and forms an expanding cone, the apex of which is at the bullet and the sides of which expand out at the speed of sound.

 

The inner angle of the shockwave cone is related to the velocity of the bullet with faster velocities having a smaller internal angle given by the formula

θ_m = arcisne (1 / M)

where θ_m is the inner angle and M is the Mach number and equal to V/c where V is the velocity of the bullet and c is the speed of sound. As the velocity of the bullet will vary over time the shape of the cone will in reality be somewhat curved.

 

I am not having much success at embedding images into this but I have attached (I hope!) a Word version of this with relevant diagrams and a straightforward overview and relevant schematics can be found at Maher (2006)³

 

The shockwave expands out in a direction perpendicular to the shockwave. This creates a zone of shockwave shadow which expands out from the muzzle at the same angle as the inner angle. A good illustration of this point can be found in the HSCA discussion of the acoustic evidence²

 

To give an example, imagine a shot fired horizontally and straight out from a window (i.e. in a direction perpendicular to the wall). If the inner angle for the particular bullet is 30^o there will be a zone that extends out from the muzzle at an angle of 30^o in all directions. Locations within this shadow zone will not experience the shockwave but will hear the muzzle blast. Locations further away from the wall will experience both the shockwave and the muzzle blast.

 

An important factor is the orientation of the shot. If the weapon is angled down at (say) 30^o the shockwave will be felt at a point at the base of the wall directly below the window (in our example where the inner angle is also 30^o). Similarly, the angle of orientation of the rifle horizontally will also influence the locations that lie in the shadow zone.

 

Table 1 summarises some examples of inner angles for different bullet velocities using the speed of sound relevant for Dealey Plaza at the time of the assassination (1123 feet per second). In practice lower bullet velocities (larger internal angles) lead to a larger shadow area which in turn allows for a greater range of possible locations.

 

Table 1: Table of shockwave inner angles for a range of bullet velocities where c = 1123ft/sec.

bullet velocity (ft/sec)	M	inner angle (degrees)
2000	1.7809	34.2
2100	1.8700	32.3
2200	1.9590	30.7
2300	2.0481	29.2
2400	2.1371	27.9
2500	2.2262	26.7
2600	2.3152	25.6
2700	2.4043	24.6
2800	2.4933	23.6
2900	2.5824	22.8
3000	2.6714	22.0

 

 

Application to the second shot at approximately Z204:

This is the point in this discussion where I would really need cartographic skills to illustrate the point properly. I will however try to summarise the main points and ask readers to challenge or develop the analysis as appropriate.

 

If you construct the relevant angles from any location in the building on the east side of Houston (DalTex, Dallas County Records, Court House) and apply a wide range of possible bullet velocities (lower velocities equate to a larger internal angle for the shockwave) I would suggest that the shot could not have come from any of those buildings. This result came as a surprise to this writer as, prior to undertaking this analysis I had thought the most likely location for the third shooter was in one of those building (and had personally been inclined to the DalTex).

Any location in the TSBD would be consistent with the absence of a shockwave, however. Practical considerations come into play in that the shot is exceptionally unlikely to have come from an open area which suggests (but does not formally prove) that there may well have been an additional shooter in the TSBD. Some additional considerations include:

• Target visibility around Z204 suggests a location some distance away from the 'sniper's nest’ itself (the tree blocking the line of sight at this time).

• The roof doesn't seem to be a practical location (see the testimony around Roy Truly and Officer Baker heading up there and mentioning that the wall was sufficiently high to need to step up on cracks in the brickwork to look over the top).

• The Seventh floor doesn't seem to have had an open window at the critical moment.

• Lower floors tended to have more people on them.

 

Preliminary conclusion:

Overall, therefore, my provisional proposal is that the most likely scenario was an additional shooter located in the TSBD and probably further west on the 6th floor. There is some limited witness evidence consistent with this possibility (the man in the brown coat) but numerous problems - not least the absence of a second weapon recovered from the TSBD.

 

I would be very grateful for any constructive challenge to this hypothesis or suggestions as to how to improve it further. I am also happy for anyone to take the basic idea and develop it up themselves if they have the relevant skills.

 

References:

 

1. Thomas, D. B., 2011, ‘Hear no Evil’, Mary Ferrell Foundation Press.

2. House Select Committee on Assassinations Report, 1979, Volume VIII, ‘Analysis of Recorded Sounds Related to the Assassination of President John F Kennedy’, https://www.history-matters.com/archive/jfk/hsca/reportvols/vol8/pdf/HSCA_Vol8_AS_2_BBN.pdf

3. Maher, R.C., 2006, Summary of gunshot acoustics, Montana State University. http://www.montana.edu/rmaher/publications/maher_aac_0406.pdf

The third shooter note for education forum.docx

[Steve Thomas]

3 hours ago, Anthony Mugan said:

 

Background on the significance of the absence of a shockwave:

The inner angle of the shockwave cone is related to the velocity of the bullet with faster velocities

 

Table 1 summarises some examples of inner angles for different bullet velocities using the speed of sound relevant for Dealey Plaza at the time of the assassination

Anthony,

 

Congratulations on your first post. It was cogent, articulate and respectful.

Thank you.

 

I am algebraically challenged, but I did have one question. Wouldn't different guns with different shot loads also have a bearing on shot velocities?

 

Steve Thomas

[Anthony Mugan]

Hello

There will be many different factors that influence bullet velocities. The key thing here is that for a given velocity there is then a corresponding internal angle to the shockwave (for a given speed of sound). That then determines the area of shadow.

What was interesting is that for even very low velocities (for rifle ammunition) the absence of a shockwave rules out the buildings on Houston. It is the lower velocities / larger internal angles that define the limiting conditions as that gives the most scope for including as many locations as possible in a particular shockwave shadow.

 

Thanks

 

Anthony

[Larry Hancock]

An interesting point of corroboration for that scenaio ( one I pointed out to Anthony on my blog) is the photo of the south side of Elm street where a bullet track was reported in the grass and where a crime scene inquiry was conducted (but never documented).  This is the area where the fellow is photographed picking something out of the grass and putting it into his pocket. 

In an associated photo, the two men - who have examined something in the grass - are pointing back and looking to what can only be presumed to be their idea of where the bullet came from and they are most definitely pointing at the opposite end of the TSBD than the purported snipers nest.

[Anthony Mugan]

Larry

An interesting thought...I’ll have look at the line of sight angles from different z frames time points around that.

thanks