linked - Investigating the Terror

No database exists at the FBI that correlates specific VODs with particular
damage or with the many other variables identified by Williams. We
conclude that Williams in fact has no objective basis for estimating a
specific VOD from an inspection of the crime scene.
Accordingly, we conclude that Williams' specific VOD opinion of 14,000-
15,500 feet per second for the main charge at the World Trade Center
lacked an adequate scientific and empirical basis.
b. Identification of the Main Charge
Having testified that the VOD of the Trade Center explosive was 14,000 to
15,500 feet per second, Williams went on to testify about the type of
explosives that fit that range. We will first summarize that testimony and
then analyze it.
(1) Williams' Testimony
On direct examination, Williams testified as follows:
Q. Based on the damage and your estimated velocity of
detonation, did you form a conclusion as to what type of
explosive was used?
A. Yes. Immediately because of that type of damage without
doing any type or having any knowledge of chemical residue
analysis, the type of explosives that fit in that bracket are very
limited. . . .
So within that parameter of 14,000 to 15,500 feet per second
we're limited to the fertilizer-based explosive such as
ammonium nitrate, and also, certain dynamites, the ammoniumnitrate
type dynamites. Perhaps on one end of the spectrum or
the other end of the spectrum we may find something like water
gels, a slurry or an emulsion. Each of these kind of explosives
are commercially available and do specific damage, but their