Examination of Firearms Review: 2007 to 2010 - Interpol

shooting incident reconstruction. Using a similar strategy in the particular case of
a victim shot in the head, the examination of hairs using SEM/EDX can give
information about the firing distance since at close distance GSR particles were
found in the inner surfaces of the cuticle (133).
Lead Check® swabs – a commercial test based on the sodium rhodizonate test
and developed at first for in field detection of high concentrations of lead in paint
and building materials – have been tested for crime scene application (134). The
swabs were applied on different materials (for effectiveness) and with different
metals (for selectiveness). It was shown that the test performed equally well,
compared to the traditional sodium rhodizonate test. In the same manner two
other commercial tests for lead and copper have been tested: Plumbtesmo® test
(designed for lead deposits in motor vehicles tailpipes) and Cuprotesmo® test
(designed for detection of copper on surfaces) (135). It was shown that i) the
Plumbtesmo® test performed as well as or even better than the sodium
rhodizonate test, and ii) the Cupresmo® test and dithiooxamide had comparable
performances. The facility of use makes these tests well adapted for in field
analysis.
The examination of histological sections can also give an idea about the firing
distance: In reference (136), the histological sections were stained using sodium
rhodizonate in order to count and measure the GSR particles in the epidermal
and subepidermal layers. A relation between firing distance and the size of
particles could be pointed out.
Some procedures using the sodium rhodizonate test recommend the application
of a 15% acetic solution onto a piece of filter paper that is then pressed against
the area of interest (transfer method). The transport of an acetic solution can be
problematic (e.g. travel by air) when the tests have to be performed in the field.
Lau (137) suggest the replacement of 15% acetic acid by commercial vinegar
available from any supermarket. However if lead around the bullet hole is
correctly detected using this reagent, the lead cloud (for distance determination)
around the hole may not be detected.
The Griess test is a colour test sensitive to nitrites. It is routinely used in many
forensic laboratories but is not as developed as the sodium rhodizonate test
since it suffers from some limitations. Lau (138) tested different formulations and
replaced successfully the desensitized photographic paper usually used for
transfer medium by blotter paper.
Colour tests usually necessitate transfer techniques rather than direct pattern
development since the contrast could not be high enough for dark fabrics.
Consequently the lack of precision of the colour tests can be due to the loss of
GSR during the transfer, causing an overestimation of the distance of firing when
comparing with test firings. In order to minimize this issue, De Forest et al. (139)
propose a direct detection of GSR based on the property of lead (and antimony)
33