Examination of Firearms Review: 2007 to 2010 - Interpol

visible contrast (this principle is highly similar to vacuum metal deposition). Chemical
information was obtained through the MALDI-ToF-MS equipment. For this study,
highly sebum-rich fingermarks from one donor were used by pressing the fingertip for
ten seconds on a substrate. Contaminated fingermarks were also obtained by putting
the fingertip in contact with drug powder for 20 seconds before pressing it on a
substrate. Finally, experiments were conducted on superimposed fingermarks by
artificially enriching each fingermark with a specific lipid (i.e., stearic acid for the first
one and oleic acid for the second one). Unfortunately, these protocols are far from
being realistic and degrade therefore the quality of the observations made.
3 Miscellaneous
Survival and transfer of bacteria has been tested on three biometric readers
(Recognition Systems HandKey III, Crossmatch Verifier 300 LC and TechSphere VP-
II S). Two strains of bacteria were tested independently of each other: Escherichia
coli and Staphylococcus aureus. For the survivability test, a known concentration of
bacteria was applied to the devices (after sterilization) and recovered by a single
touch with a finger covered with a sterile finger cot after 5, 20, 40 and 60 minutes.
For the transferability test, the device was touched 50 times with a finger, and
contamination of the device occurred prior to touch number 11. The survivability
study shows that at five minutes past contamination, 15% of the Staphilococcus
aureus remain on the fingerprint reader (and 20% and 40 % for the vein and hand
geometry readers, respectively); after 20 minutes, the survival rate was almost zero.
For Escherichia coli, the percent survival after five minutes is 28% for the fingerprint
reader (it is 40 and 50% for the hand geometry and vein readers, respectively).
Again, after 20 minutes, the survival rate approaches zero. The number of cells
transferred decreases over successive touches; most of the bacteria are transferred
within the first ten touches (371)
The relationship between oiliness, humidity, elasticity of the skin and image quality
has been investigated using 190 individuals, 6 impressions per individuals and 9
fingerprint sensors (4 capacitance, 4 optical and 1 thermal). The skin moisture,
oiliness and elasticity were measured with a Triplesense device. While differences
appear between the different sensor technologies, the relationship between skin
moisture, oiliness and elasticity and image quality is not linear (372).
The important factors in fingerprint scanners with respect to image quality (quality
being defined with respect to the accuracy of automated fingerprint recognition) have
been investigated. The main quality parameters defined by the FBI are used, and
images are acquired and then degraded with respect to each of these parameters.
No significant drop in performance (with respect to the ideal case) was observed
when all parameters were set to the IAFIS IQS minimum requirements (but
acquisition area is not defined); The PIV IQS requirement for the acquisition area
allows a drop in performance when the minimal requirement is used. The three most
critical parameters are acquisition area, output resolution, and geometric accuracy.
When these three parameters were degraded simultaneously, the drop in
performance was larger than the sum of the individual performance drops. (373)
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