Examination of Firearms Review: 2007 to 2010 - Interpol

Columbaros et al. (85) use TOF-SIMS to evaluate the elemental variation across
and through a sheet of glass, particularly the non-float surface. TOF-SIMS offers
the potential for analyzing glass fragments as small as tens of microns across.
As with RI, there is measurable variation with TOF-SIMS analysis between the
surface and bulk. This supports the practice of avoiding surface fragments when
conducting RI analyses. Results show that evaluating the non-float surface is not
straightforward, and certainly not representative of the bulk. The authors
recommend that when techniques such as SIMS are used, which operate to
depths measured in nanometers, extra caution should be used to avoid type I
errors and suggest eroding the surface to expose the bulk.
Nakanishi et al. (86) explore the use of synchrotron radiation high-energy X-ray
fluorescence (SR-XRF) spectrometry for the nondestructive discrimination of
glass. SR-XRF offers the advantage of extremely low detection limits for some
elements, but those values had not yet been quantified. This study was
undertaken to discover the lower limits of detection for elements found to be
discriminating for glass. Detection at the pictogram (pg) level was possible for
Ba, Ce and Sm, and at the 10-pg level for Sr, Zr, Sn and Hf. The elements Ca,
Mn, Fe and Sn were not used as they had unacceptably high relative standard
deviations (greater than 10%). In general, however, satisfactory discrimination
was achieved and the technique was determined to be effective for a
nondestructive analysis of trace amounts of heavy elements contained in a
minute sample. Currently, this instrumentation is not readily available to forensic
laboratories.
A feasibility study by Bell, Nawrocki and Morris (87) uses cathodoluminescence
(CL) spectroscopy to discriminate between different glass sources. Using this
method in conjunction with RI analysis, all window and container glasses of the
sample set were differentiated as were six out of ten headlamps. Inter- and intrasample
variation of several NIST reference glass standards was determined.
The reference glasses were readily distinguishable by this method, but some
intra-sample variation was observed. Although non-destructive, fairly
inexpensive and easy to operate, CL is hampered by lack of standards and
databases, and relatively low spectral resolution. Also, the relatively limited
forensic applications of CL make it unlikely that CL will become standard in
forensic laboratories. This work was also presented by Barron and Bell (88) at
the 2008 AAFS meeting in Washington, D.C.
5. Transfer and Persistence
There were relatively few published studies on the transfer and persistence of
glass during the reporting period. Those that were published were targeted to a
particular environment in hopes of establishing relative populations for likelihood
ratio calculations. In general, these studies reaffirmed other recent studies
indicating that most of the clothing in the general population is free from glass
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