Examination of Firearms Review: 2007 to 2010 - Interpol

Li et al. also use the Fast Fourier Transform (FFT) for analyzing the line-scan
imaging technique of projectiles (48). In (49) the line-scan technique is compared
with laser depth proofing and photonic 3D topography.
Blechko and Darker et al. discuss the ability of lay and experienced operators,
and an automated vision method to detect an individual carrying a (concealed)
firearm in simulated CCTV footage (closed circuit television); see e.g. (50,51,52).
They conclude that although several issues remain to be investigated or
improved further: (i) a human observation inspired method would most likely be
the most successful automated method, (ii) a combined automated and human
approach may offer potential for realizing the given detection task in real-life, and
(iii), the decision making process whether a person is carrying a concealed
firearm appears to be linked to the emotional state of the observed person.
Chu et al. studied striation densities in images obtained for six lands of 48 bullets
fired from 12 gun barrels of six manufactures (53). They conclude that their
statistical results show a strong support for a relationship between identification
rate and striation density. The authors offer that their method can thus provide a
quantitative criterion to assess whether sufficient striae are present in order to
achieve reliable bullet identification.
ii. Equipment
Katterwe et al. introduce comparison scanning electron microscopy in forensic
science and demonstrate the applications for firearms (and tool mark) examiners
(54). The comparison VP-SEM (Variable Pressure – Scanning Electron
Microscopy) consists of two separate SEM that are linked so that an image of the
second can be displayed alongside an image of the first. Due to its high
resolution and depth of field, the system allows for detailed comparison of
specimens. Examples are manifold: cartridge cases and bullets but also cut
adhesive tapes and other applications. Samples can be either conductive or nonconductive.
As it comes to harmonising results from proficiency tests, it is important that all
participants are looking at the exact same samples. For this reason an advanced
casting technique was developed by Koch and Katterwe (55). In their article they
present the “3D-mass-produced casting procedure”, including the construction
and manufacturing of the used devices.
2.1.6 Court rulings
Particularly the firearms and tool marks examiners in the USA are regularly
challenged in court to defend the scientific principles of the discipline. The
Defense will often motion for a Frye or Daubert hearing to exclude the evidence.
The Scientific Working Group Firearms (SWGGUN) is keeping track of these
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