Forensic Lab Investigations
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Transcript of Forensic Lab Investigations
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Forensic Lab Forensic Lab InvestigationsInvestigations
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FingerprintingFingerprinting
Been used for identification since the Been used for identification since the early 1900searly 1900s
FBI Identification division began, in FBI Identification division began, in 1924, with 810,188 fingerprint files1924, with 810,188 fingerprint files
Currently, more than 250 million Currently, more than 250 million fingerprint recordsfingerprint records
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BackgroundBackground
Skin on palms, fingers, and feet have Skin on palms, fingers, and feet have tiny surface ridgestiny surface ridges
Gives traction for walking and Gives traction for walking and graspinggrasping
Pattern is unique to each personPattern is unique to each person
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Why do we leave prints?Why do we leave prints?
Skin surface covered with oils, sweat, Skin surface covered with oils, sweat, and amino acids which transfer to an and amino acids which transfer to an object when touchedobject when touched
Foreign substances (oil, blood, dirt, Foreign substances (oil, blood, dirt, ink, etc.)ink, etc.) Exact impression of surface ridge is left Exact impression of surface ridge is left
behindbehind
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Can your fingerprints change?Can your fingerprints change?
No, fingerprints will always remain No, fingerprints will always remain the same.the same.
They may scar or have cracks.They may scar or have cracks. Can be masked with super glue or Can be masked with super glue or
burnt off, but they will returnburnt off, but they will return
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Matching PrintsMatching Prints
There are no set matches of points There are no set matches of points that must be provided for courtthat must be provided for court
The more you have the more The more you have the more convincing your evidenceconvincing your evidence
Must show how the points matchMust show how the points match
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Types of PrintsTypes of Prints
Fingerprint ImpressionFingerprint Impression Arch, whorl, loopArch, whorl, loop Categories:Categories:
Loop, double loop, central pocket loop, Loop, double loop, central pocket loop, tented arch, plain arch, plain whorl, tented arch, plain arch, plain whorl, accidentalaccidental
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In a In a whorl patternwhorl pattern, the ridges are usually circular, the ridges are usually circular In a In a loop patternloop pattern, the ridges enter from either , the ridges enter from either
side, re-curve and pass out or tend to pass out side, re-curve and pass out or tend to pass out the same side they enteredthe same side they entered
In an In an arch patternarch pattern, the ridges enter from one side, , the ridges enter from one side, make a rise in the center and exit generally on make a rise in the center and exit generally on the opposite sidethe opposite side
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Tented ArchTented Arch
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Can you identify these prints?Can you identify these prints?
A
B
C
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Minutiae (Galton) PointsMinutiae (Galton) Points
Ridge characteristics that go into a Ridge characteristics that go into a little more detail than the arch, loop, little more detail than the arch, loop, and whorl classificationand whorl classification
Used for more precise identificationUsed for more precise identification
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Types of PointsTypes of Points
Basic and
composite ridge characteristics
(minutiae)
Minutiae
Example
Minutiae
Example
ridge ending
bridge
bifurcation
double bifurcation
dot
trifurcation
island (short ridge)
opposed bifurcations
lake (enclosure)
ridge crossing
hook (spur)
opposed bifurcation/ridge ending
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Using Minutiae PoinntsUsing Minutiae Poinnts
Compare prints of Compare prints of the same finger the same finger and classificationand classification
One print may One print may have as many as have as many as 100 minutiae 100 minutiae pointspoints
No two fingers No two fingers have the same have the same patternpattern
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http://shs.westport.k12.ct.us/http://shs.westport.k12.ct.us/forensics/04-fingerprints/forensics/04-fingerprints/handout.htm handout.htm
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Latent PrintsLatent Prints
Fingerprints found on a Fingerprints found on a surface that aren’t visible to surface that aren’t visible to the naked eye.the naked eye.
Flashlight, UV light, or laser Flashlight, UV light, or laser used to find printsused to find prints
Dusting procedure is most Dusting procedure is most effective if prints are oily effective if prints are oily (50% of the time)(50% of the time)
Must be done carefully to not Must be done carefully to not destroy the printsdestroy the prints
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http://criminaljustice.state.ny.us/http://criminaljustice.state.ny.us/ojis/history/fp_sys.htm ojis/history/fp_sys.htm
http://en.wikipedia.org/wiki/http://en.wikipedia.org/wiki/Henry_Classification_System Henry_Classification_System
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