Forensic study by Bergen County Academies High School

[Margo]

Possible Skin Fragment Evidence is Found in Incomplete Fingerprints
A. Villena,* A. Calabro,** D. Becker,** J.Morales***
* Bergen County Technical High School, Law and Justice Department, 504
Rt. 46 West, Teterboro,NJ 07608
** Bergen County Academies, Microscopy Laboratory, 200 Hackensack
Avenue, Hackensack, NJ 07601
*** City College of New York, Electron Microscopy Facility, 160
Convent Avenue, New York, NY10031
Latent fingerprints are chance or accidental impressions left by
friction of skin ridges on a given surface. Incomplete prints may be
in inadmissible as evidence, limiting their usefulness in forensic
science. We have conducted observations by scanning electron
microscopy to determine if skin fragments may be found in incomplete
fingerprints. Such skin fragments may be used as a source of DNA for
genetic identification.
Prior to making a fingerprint, hands were washed and dried off with a
paper towel. The substrate (aluminum or glass slide) was cleaned with
alcohol, dried with Kimwipes and dusted off with pressurized gas
(DustOff). The right thumb was then pressed against a 25 mm aluminum
SEM stub
or a glass slide. Prints made on aluminum pins were observed without
any coating at 2 kV in high vacuum mode. Prints made on glass slides
were carbon coated and observed in high vacuum mode at 30 kV. An FEI
Quanta 200 3D SEM was used to obtain secondary electron micrographs.
As a control, small pieces (1mm) of skin were mounted on SEM pins with
carbon tape and observed, uncoated at 30 kV.
Observations made of prints show the presence of oil droplets along
the skin ridge imprint (Fig.1AD) and the presence of particles (Fig.
1C-E) along the ridges. These particles (Fig. 1C-E) are similar in
morphology to control skin fragments (Fig. 1F and G). The flattened
morphology of the particles found in prints (Fig. 2C-E) is consistent
with the flattened morphology of squamous epithelial cells
known to be present on the skin surface (Fig. 1F-G). Although,
charging could have been eliminated by working in low vacuum mode, we
found that charging was helpful in making the particles or skin
fragments more identifiable. Some of the skin fragments found in
prints were as long as 67 um (Fig 2E). Similar results were obtained
from prints made on glass slides (results not shown).
Fingerprints have already been used as potential sources of DNA for
genetic identification (Balogh et al, 2003). The collection of
microscopic skin fragments from fingerprints followed by DNA
fingerprinting could help law enforcement and forensic scientists link
a particular suspect to a crime,
even if the print is incomplete and/or smudged.
Cited Reference:
M.K. Galogh, J. Burger, K.Bender, P.M. Schneider, K.W. Alt, 2003. STR
genotyping and mtDNA sequencing of latent fingerprint on paper.
Forensic Science International 136:188-195.
Microsc Microanal 15(Suppl 2), 2009
doi: 10.1017/S1431927609099401 Copyright 2009 Microscopy Society of
America 620

FIG. 1. Secondary electron micrographs of a fingerprint (A-E) and a
skin fragment (F-G). Panels A and B are low magnification images of a
partial fingerprint, notice the impressions made by skin ridges. At
higher magnifications fragments of skin may be observed along the
impressions made by skin ridges (C-E). All specimens were observed in
high vacuum mode without metal or carbon coating. Charging is a
desirable artifact in this case since it helps locate skin fragments
along the ridges.
Microsc Microanal 15(Suppl 2), 2009 621