Examination of Firearms Review: 2007 to 2010 - Interpol

combination with a mechanical technique, such as lifting tape. Washing under water,
ultrasonic bath, or use of organic solvents (e.g., chloroform or xylene) are not
recommended since they induce damage to latent fingermarks. It should finally be
noted that the soot can make fingermarks already visible. A careful examination
should therefore precede any further treatment (soot removal or application of a
fingermark detection technique).
The possibility to recover fingermarks on paper exposed to elevated temperatures
was also conducted (300). Five donors deposited non-enriched fingermarks on white
paper. The marks were allowed to age from one hour to one month before being
heated to temperatures ranging from 50 °C to 200 °C, for 10 to 320 minutes. 200 °C
has been chosen as maximum temperature since paper auto-ignites at ca. 233 °C.
DFO, ninhydrin and physical developer were further applied when attempting to
detect latent fingermarks. The results showed that some fingermarks were readily
visible after the heating process, especially at 150°C and 200°C. Moreover, the
marks subjected to 150 °C were naturally fluorescent when excited at 473 to 548 nm
and observed using a 549 nm filter (no fluorescence was however observed for the
substrates exposed to 50, 100, and 200 °C). Successful results were obtained with
the chemical methods for exposure conditions up to 200 °C for ca. five or six hours.
DFO is the recommended technique for exposure temperatures below 100°C, and
physical developer above 100 °C. The substrate could also be processed with PD
subsequently to DFO. If the substrates have been wetted during the extinguishing of
the fire, PD is to be applied whatever the exposure temperature.
The natural fluorescence of fingermarks on paper exposed to elevated temperature
has been further studied by the same team (303). Three kinds of fingermarks (i.e.,
eccrine, sebaceous, and “natural”/ungroomed) on white and filter papers were
exposed to temperatures ranging from 110 °C to 190 °C, for 20 minutes. It was found
that eccrine sweat was most subjected to fluorescence between 130 to 180 °C, with
a maximum intensity obtained for the 160-180 °C range. It is hypothesized that
thermal degradation of some amino acids could be at the origin of the observed
luminescence. Sodium chloride and urea also fluoresced upon exposure to elevated
temperature. Optimal observation conditions were determined as being: excitation
source of 352 to 509 nm, combined with an observation filter of 510 nm.
Considering the effect of fire on fingermarks in blood, Moore et al. showed that some
of the commonly used protein stains (i.e., acid black 1, acid yellow 7, and acid violet
17) continue to be efficient in detecting marks in blood for exposure of the
fingermarks up to 200°C, while heme-specific reagents (such as LCV) stopped giving
positive results between 100 and 150°C (301 pp. 64-82, 2009] #577). Various
substrates were considered (e.g., paper, cotton fabric, ceramic tile, smooth
melamine, metal) and defibrinated horse blood was used to create depletion series of
blood fingermarks. Eighteen hours after deposition, the fingermarks were exposed to
100 to 300 °C in a laboratory oven, and to 400 to 600 °C in a high-temperature
furnace, for one to eight hours. Commonly used detection techniques were tested,
specific for blood or not (i.e., acid black 1, acid violet 17, acid yellow 7, DFO,
Leucocrystal violet - LCV, PD, VMD, cyanoacrylate with dye, solvent black 3, and
powder suspensions). The recommended techniques are acid black 1 and acid violet
17 for the processing of porous and non-porous surfaces, respectively. Interestingly,
above 200°C, it is still possible to detect some marks but it becomes impossible to
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