Examination of Firearms Review: 2007 to 2010 - Interpol

one day of immersion, PD failed in detecting identifiable marks (contrarily to ORO).
For natural marks, both techniques performed equally (in few cases, PD even
developed better marks than ORO). This could be explained by the fact that PD
targets more constituents than ORO (which only stains lipids). Finally, no difference
was observed between the three kinds of water that were used. Additionally, the role
played by the paper type is minor, at the exception of the card for which only natural
marks of low quality were obtained.
The efficiency of a commercially available PD processing kit (brand: Sirchie
Fingerprint Laboratories) and a “home-made” PD solution have been compared on
different porous substrates (236). It has been concluded that both the commercial
and the non-commercial solutions were competitive and acting equally in terms of
fingermark quality (contrast and clarity), the commercial formulation being somewhat
more sensitive when less secretions are to be detected. Nevertheless, a drawback of
the commercial solution could arise if one wants to enhance the results using
potassium iodide (KI) to darken the background (if it contains starch) while lightening
the marks. Indeed, such post-treatment must be photographed while the substrate is
submerged in the solution. Given that the tested commercial PD solution was
opaque, the resulting contrast was considerably reduced.
2.2.5 Dry micron-sized powders and powder suspensions
Some contributions were dedicated to the traditional, dry and micron-sized
powders. It is possible to cite the works performed on skin (237) and fruits
or vegetables (238), as well as the propositions of new powders based on
phosphorescent compounds (239), on banana peel activated carbon
(240), or on dye-doped silicate clay powder (241). Most of the publications
were dedicated to powder suspensions (SPRs), used to detect marks on
wetted non-porous substrates. Comparison studies were conducted
between commercially-available SPRs (242-245), as well as between SPR
and vacuum metal deposition (246). Original research led to the
proposition of a luminescent SPR (247), and the relation between the
smoothness of a surface and its processing using SPR has been
investigated (248). Finally, it was observed that wiping an SPR-processed
surface with a paper towel makes new marks appear (249).
Trapecar et al. illustrated the efficiency of some fingerprint powders (especially the
Swedish Black powder) to successfully detect fingermarks on skin (237) and fruits or
vegetables (238), compared to chemical techniques such as cyanoacrylate fuming
and ruthenium tetroxyde. For both studies, non-enriched fingermarks from several
donors were left by prolonged contact with the items (several seconds), and were
aged from 15 to 45 minutes for living bodies, from 15 to 180 minutes for dead bodies,
and from hours to two days for fruits and vegetables, before being processed.
Liu et al. proposed a new phosphorescent powder based on a europium-doped
strontium aluminate. This phosphorescent powder could be of a first interest in the
case of fluorescent or multicoloured substrates that generally lead to an unwanted
decrease of the resulting contrast when using traditional luminescent powders (239).
For this study, fresh and aged fingermarks (up to two-month-old marks) from different
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