Examination of Firearms Review: 2007 to 2010 - Interpol

caution about the environmental sensitivity, namely fluctuating precision with
temperature, humidity, etc., of the GRIM. The authors correctly indicate that if all
fragments from a given case are analyzed on the same day users may be able to
avoid problems associated with extensive instrument drift.
Krieghoff (33) discussed his experiences with the new LUCIA RI: Refractive
Index Measurement System as compared to the GRIM system.
Zadora (34) describes the application of Bayesian nets to continuous data. A
Bayesian net is a graphical model used to show whether two sets of data, RI of
glass in this case, could share a similar source.
In Delft and St. Gallen, Zadora (35, 36) demonstrated software (calcuLatoR)
used to calculate a likelihood ratio using univariate (RI) data. While this offers
the glass analyst a simple solution to the difficulty of calculating a likelihood ratio,
analysts should not use this program without a thorough understanding of the
variables used and underlying assumptions of the method.
Zadora and Neocleous (37) compared various methods of databasing univariate
data for within-object variability and their effects on likelihood ratio determinations.
Most forensic laboratories use in-house databases to test within- and betweenobject
variability. These are generally constructed using a relatively small
sample set, usually from case work, to represent a larger object or objects.
While databases of this kind may not necessarily represent the exact population
of broken glass for a given case, the authors concluded that databases
generated in this fashion are appropriate to use for likelihood ratio calculations.
Dätwyler, Fehr and Ivo (38) used total reflection x-ray fluorescence (TXRF) for
elemental analysis of glass. While this technique allows for detection limits in the
parts per billion (ppb) range for many elements, the precision is strongly
dependent on appropriate sample preparation. Samples prepared in
suspensions varied less than powdered glass samples placed directly on a
sample holder.
Additionally, the EPG commenced publishing an annual newsletter. In the 2009
edition, Becker (39) edited and published “The forensic analysis of float-glass
characterization of glasses from international sources.” Originally presented by
Wilfried Stoecklein at the 1997 Trace Evidence Symposium in San Antonio,
Texas (USA), the proceedings from that conference, while often discussed, were
never published. The work carried out by the BKA in forensic glass analysis in
the 1990’s is reported therein.
2.2.6 NIJ Symposia
In August 2007, the US NIJ and the FBI Laboratory sponsored a symposium
entitled “Making the Case with Trace Evidence” in Clearwater, Florida (USA), an
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