Examination of Firearms Review: 2007 to 2010 - Interpol

In (31) Sakarya et al. discuss the use of photometric stereo for reconstruction of
3D cartridge case surfaces. In this paper the 3D information is obtained from
multiple 2D images which are acquired using a specially designed set-up. The
authors further describe the radiometrical calibration, photometric stereo, and
surface fitting methods used for translating the 2D information into a 3D surface.
The resulting method is low cost (as compared to e.g. laser interferometry or
profilometry) and not time-consuming. Unfortunately, no comparison of the
accuracy of this method, nor its relevance for performing real-life visual or
automated matching in case work or database searching is included.
Recent advances in 3D tomography techniques have resulted in multiple authors
examining the use of these methods for studying incidents in which ballistic
projectiles were involved. In (32) the use of cone-beam computed tomography
(CBCT) is compared to multi-slice computed tomography MSCT/MDCT. The
authors conclude that CBCT can be an important diagnostic tool for the
evaluation of gunshot injuries, especially for detecting structural hard-tissue
damage around or nearby projectiles, and for determining the precise location of
a projectile in a body. Thali et al. (33) applied 3D MSCT in a case concerning an
illegal lynx shooting and argue that it is a suitable and promising new technique
for veterinary pathology. Puentes et al. (34) used 3D MSCT in a non-fatal case
where a man was shot in a multiple aggressor situation. They used this method
to accurately determine the bullet’s trajectory. In (35) a CT scanner is used to
analyze the cavities and the fragmentation and dispersal pattern of the projectiles
that occurred after discharging a firearm in commercially purchased ballistic
glycerine soap blocks. The authors argue that this method offers a fast and
accurate analysis that also avoids issues such as e.g., the possible drying or
shape alteration of a block that can occur when using a traditional examination
process.
De Smet et al. (36) discuss the use of both traditional optical and 3D measuring
techniques to investigate if the initial seating depth of the primer has an impact
on the variability of the marks found on the breech face.
They conclude that for the circumstances under which they tested (i) no clear
impact on the primer striation patterns could be found, but that (ii) differences in
the firing pin impressions could be noted. In this work 3D measuring did not yield
important additional information for arriving at these conclusions.
Song and Vorburger continue their earlier work on topography measurement
techniques. In (37) they propose a new “profile difference” parameter for
measurement and comparison of 2D and 3D surface topologies. They also
studied the topography decays and the impact of the electro-forming technique
used by the National Institute of Standards (NIST) to produce their standard
reference material (38). They conclude that for the 256 casings under
consideration it can be expected that they are replicated with a proposed
CCFmax correlation rate of higher than 95%.
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