Dactyloscopist
Fingerprint expert
Evidence
• 3 different kinds of fingerprints
– Latent Prints
– Patent Prints
– Plastic Prints
Latent Prints
• A chance or accidental impression left by skin
on a surface
• Chemical, Electronic, and physical processing
techniques show visualization of the invisible
print
• Print comes comes from sweat, motor oil,
blood, paint, ink…
• Very valuable physical evidence
Latent Print
Patent Prints
• Friction ridge impressions of unknown origins
• Transfer from a foreign material on a finger
onto a surface
• Visible
• Photographed rather than lifted
• Ex: ink, dirt, blood…
Patent Prints
Plastic Prints
• Friction ridge impression from
– Finger
– Palm
– Toe
– Foot
Keeps the shape of the ridge detail
Ex: melted candle wax, thick grease
Visible and doesn’t need photography
Plastic Prints
Fingerprint Capture
• The machine mainly determines the difference
in the ridges and the valleys
• Two kinds of readers
– Solid-state fingerprint reader
– Optical fingerprint reader
Classifying fingerprints
• 4 different kinds of fingerprints:
– Arch
– Loop
– Whorl
– Tented Arch
Arch
Loop
Whorl
Tented Arch
Case Study: Conviction Through
Enhanced Fingerprint Identification
• In 1990 an unknown assailant sexually
molested and fatally stabbed a young woman.
The only evidence was a pillowcase, found
next to the victims body. It had several blood
stains, one stain showed some faint
fingerprint ridge detail.
Investigation
• Pillowcase to the departments forensic unit
for bloodstain pattern analysis
• Stains were consistent with a knife blade
• Fingerprint had enough ridge detail to go
further into the investigation
• Image enhancement developed likely suspects
and the the DNA proved the fingerprint match
was correct
Interview
• “What kind of educational background do you
have to have in order to work as a fingerprint
expert?”
• “It depends, there are different levels. There is on
the job training and job preparation training;
NCIC National Crime Index Certification and
International Association of Identification. The
person with the least amount of experience has
worked here for 7 years.”
• “What is a typical day like for you?”
• “It depends, I examine fingerprints of
individuals that are arrested and process their
identification to check their previous arrest
history. I also review the work of coworkers to
make sure they make proper identifications.”
• “Are you a forensic specialist all the time or
do you have a "day job"?”
• “There are different shifts. There is a late unit
and a temperate unit which is 24 hours. There
are three 8 hour shifts each day. There is a
shift from 4am to 3 pm.”
Resources
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http://images.google.com/imgres?imgurl=http://www.fdle.state.fl.us/CrimeLab/im
ages/fingerprint
http://www.wilsonnc.org/userimages/image/00000023_image002.jpg
http://en.wikipedia.org/wiki/Fingerprint#Patent_prints
http://static.howstuffworks.com/gif/safecracking-keypad.jpg
http://people.pwf.cam.ac.uk/jw566/research/photex/application/images/finger1.j
pg
http://www.crimeandclues.com/92dec001.htm