Examination of Firearms Review: 2007 to 2010 - Interpol

the contaminated fingertips on an aluminium-coated microscope slide. The imaging
was performed by comparing the spectra obtained from the scanned fingermarks
with the reference spectra of the targeted explosives, using Pearson's crosscorrelation.
In this preliminary study, it was possible to locate and identify explosives
from contaminated fingermarks. The consideration of realistic surfaces and the effect
of fingermark detection techniques (such as cyanoacrylate) on the subsequent
identification of explosives have to be investigated in further experiments.
Attenuated total reflection – Fourier transform infrared (ATR-FTIR) was used to
locate and identify explosive particles in latent fingermarks (321). Fingertips were first
contaminated with explosives (i.e., TNT, trinitrobenzene, or ammonium nitrate) by
touching a glass slide on which explosive powder was spread. Excessive powder
was brushed away, until no more powder was visible by the naked eye, and the
fingers were pressed on stainless steel (this substrate is transparent in the infrared
region) as well as on a more realistic substrate (i.e., metal lid from a jar). The
procedure consisted in locating (explosive) particles (as small as 20 µm) and
comparing their FTIR spectrum with an infrared spectral library. It should be noted
that sweat residue could interfere with the resulting FTIR spectrum. Similarly to this
work, the use of RDX-containing solution were used to contaminate fingertips before
they were pressed on aluminium coated slides, and further analyzed using ordinary
FTIR (322).
The use of a reflective ultraviolet imaging system (RUVIS) is reported to locate
fingermarks on post-blast material (324). The author stated that people generally look
for fingermarks on tape and batteries (used to set up the explosive device), but not
necessarily on the device itself, assuming that the heat of explosion had a strong
detrimental effect on fingermarks. In this experiment, explosive devices were
designed using C4, nitromethane and gasoline, a bag and plastic bottles. Following
the blast in open air, pieces of the explosive device were collected and observed
using a RUVIS. A single fingermark – further identified to the designer of the
explosive devices - was found on a non-porous surface (a remaining piece of a
plastic bottle). The advantage of RUVIS is that the resulting contrast is not dependent
on the colour of the substrate. Moreover, this technique can be used on-site if
explosive devices have to be destroyed in place, without a subsequent laboratory
examination capability (e.g., Irak).
2.2.15 Detection and lifting of fingermarks on skin
The detection of marks on skin has been investigated through different
environmental parameters (325) and by comparing several fingermark
detection techniques (237, 325). Swedish Black, Magnetic Jet Black
powder, or RTX spraying are recommended for use in this context (237).
The lifting of unprocessed marks from skin should be done by using
Transparent Instant lifter (237), whereas powdered marks should be lifted
by using silicone casting material (325) or white gelatin lifter (326).
Four fingerprint powders (i.e., Magnetic Jet Black, Magnetic Silver, Silver Special,
and Swedish Black) and two chemical methods (i.e., cyanoacrylate fuming and
ruthenium tetroxyde - RTX) were compared to assess their ability to detect
fingermarks on skin (237). The marks were either processed directly on skin, or lifted
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