Inconsistent Metallurgical Claims
My old bandleader at MIT, John Corley, always used to
exhort us to get the beginning and endings of pieces right because he said,
"The audience will remember the first note and the last note, not the
stuff in between." So it can be with scientific articles
as well—most readers remember the first parts and the last parts more than the
boring details in the middle.
Normally, that doesn't present a problem, because the
beginnings, middles, and ends will be consistent with each other. But not
here—the beginning and the ending of this
article
present considerably stronger statements about metallurgy than the middle
does. Its followers, most of whom are not in a position to independently
evaluate the details, are choosing to remember the beginning and the ending, and
are not realizing how critically they differ from the truths in the middle.
It starts with the very first word of the
title—"Proper." This word strongly implies that the
article is contrasting itself with earlier work that is "improper." To
illustrate the pattern of stronger and weaker claims in the rest of the article,
I have segregated them by the order of their sections in the article. Although
it is a truism, it should not be forgotten that stronger and weaker claims for
the same thing cannot both be true. All numbered sentences below are verbatim from
the article.
Abstract
(1) Microsegregation of trace and minor elements during lead casting
and processing can account for the experimental variabilities measured in
various evidentiary and comparison samples by laboratory analysts. (Strong)
(2) Thus, elevated concentrations of antimony and copper at
crystallographic grain boundaries, the widely varying sizes of grains in MC
bullet lead, and the 5-60 mg bullet samples analyzed for assassination
intelligence effectively resulted in operational sampling error for the
analyses. (Strong)
(3) This deficiency was not considered in the original data
interpretation and resulted in an invalid conclusion in favor of the
single-bullet theory of the assassination. (Absolute statement)
Introduction
(1) However, VPG did not interpret his measurements with
knowledge of basic metallurgy of lead alloys, standard lead smelting, and bullet
manufacturing processes. His conclusions are unsupported from those vantage
points. (Strong)
(2) Finally, he was unaware that the small sample size he was
constrained to contributed to variability in his measurements because some of
the elements he quantified were not distributed uniformly within the samples as
this scale. (Strong)
Trace Analysis
(1) An investigator cannot interpret the compositional
analyses without regard to the realities of bullet production. (Strong)
(2) He or she must therefore have knowledge of, or at least
consider the metallurgy of, lead alloys, lead smelting practices, as well as
ammunition distribution practices. (Strong)
Essential Metallurgy
(1) The common occurrence of segregation (both
microsegregation and macrosegregation), as discussed below, explains VPG's
observations and the variability in his measured antimony and copper data.
(Absolute statement)
MC Grain Size
(1) Using Figs. 3 and 4 as visual aids, if the sample size of
a lead specimen approaches the grain size, and the antimony and copper trace
elements are segregated at the boundaries, then the variability of sample
compositions will increase. (Strong general prediction)
(2) For example, if all samples were large enough to contain
on the order of 50 or more grains, they will encompass a good average quantity
of both grain-boundary material and interior grain material and will be
reasonably representative of the true average composition of the alloy. (Strong
specific prediction. Note that the FBI used triplicate 60-g samples to construct
its huge database on bullets, and their variabilities were typically only 3%–5%.)
(3) However, if the samples are only the size of, e.g., one
to three grains, then each sample will likely contain different relative
proportions of grain-boundary and interior grain material. This situation can
result in increased compositional variability among ostensibly equivalent
samples. (Weaker prediction)
(4) The answer to questions of whether sample sizes were
appropriate in the JFK assassination investigation, and whether they could have
contributed to variability of the results, is then effectively reduced to that
of assessing grain sizes. (Weak/strong statement)
(5) Hence, some or all of the variability seen in VPG's
antimony and copper measurements could be attributed to small sample sizes.
(Weaker statement)
(6) Certainly, 5–10 mg
samples should be suspect with respect to being representative of the bulk
composition. (Very weak statement that also appeals to a mythical "bulk
composition" that is not supported by the actual data)
(7) The end-result of these metallurgical considerations is
that, from the antimony concentrations measured by VPG in the specimens from the
JFK assassination, there is no justification for concluding that two, and *only*
two, bullets were represented by the evidence. (Very strong statement that
derives from the weaker statements above)
Conclusions
(1) The large and variable grain sizes found in bullets from
WCC MC ammunition lots 6000 and 6003 show that the 1–50
mg specimen sizes that VPG was restricted to for the JFK analyses could have
contributed to, or been the sole source of, the variability found in the
antimony and copper data. (Weak again)
(2) Hence, the relatively small differences reported in
antimony composition alone in the JFK data are not adequate to differentiate
among the possibilities of a single or multiple bullets. (Strong)
(3) ... a conclusion of material evidence for only two
bullets in the questioned JFK assassination specimens has no forensic basis.
(Absolute statement)
Overall pattern
Which of the conflicting claims to hold the article to?
It seems to me that any argument that makes stronger and weaker
claims on the same subject should be held to the strongest of the claims.
The relevant claim in
this case is the absolute claim under Essential Metallurgy: "The common
occurrence of segregation … explains VPG's
observations and the variability in his measured antimony and copper data." This
amounts to saying that Guinn was just measuring crystalline effects in the MC lead,
and that this lead was no different from any other. There were no two groups,
only random variations in antimony from crystalline effects.