Forensic Lab
Investigations
Fingerprinting
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Been used for identification since the early
1900s
FBI Identification division began, in 1924,
with 810,188 fingerprint files
Currently, more than 250 million
fingerprint records
Background
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Skin on palms, fingers, and feet have tiny
surface ridges
Gives traction for walking and grasping
Pattern is unique to each person
Why do we leave prints?
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Skin surface covered with oils, sweat, and
amino acids which transfer to an object
when touched
Foreign substances (oil, blood, dirt, ink,
etc.)
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Exact impression of surface ridge is left
behind
Can your fingerprints change?
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No, fingerprints will always remain the
same.
They may scar or have cracks.
Can be masked with super glue or burnt
off, but they will return
Matching Prints
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There are no set matches of points that
must be provided for court
The more you have the more convincing
your evidence
Must show how the points match
Types of Prints
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Fingerprint Impression
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Arch, whorl, loop
Categories:
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Loop, double loop, central pocket loop, tented
arch, plain arch, plain whorl, accidental
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In a whorl pattern, the ridges are usually circular
In a loop pattern, the ridges enter from either side, recurve and pass out or tend to pass out the same side
they entered
In an arch pattern, the ridges enter from one side, make
a rise in the center and exit generally on the opposite
side
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Tented Arch
B
A
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Can you identify these prints?
C
Minutiae (Galton) Points
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Ridge characteristics that go into a little
more detail than the arch, loop, and whorl
classification
Used for more precise identification
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Types of Points
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Using Minutiae Poinnts
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Compare prints of
the same finger
and classification
One print may have
as many as 100
minutiae points
No two fingers
have the same
pattern
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http://shs.westport.k12.ct.us/forensics/04fingerprints/handout.htm
Latent Prints
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Fingerprints found on a surface
that aren’t visible to the naked
eye.
Flashlight, UV light, or laser used
to find prints
Dusting procedure is most
effective if prints are oily (50%
of the time)
Must be done carefully to not
destroy the prints
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http://criminaljustice.state.ny.us/ojis/histo
ry/fp_sys.htm
http://en.wikipedia.org/wiki/Henry_Classifi
cation_System