Forensic Lab Investigations

Forensic Lab Forensic Lab InvestigationsInvestigations

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

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

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

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

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

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

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

Tented ArchTented Arch

Can you identify these prints?Can you identify these prints?

A

B

C

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

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

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

http://shs.westport.k12.ct.us/http://shs.westport.k12.ct.us/forensics/04-fingerprints/forensics/04-fingerprints/handout.htm handout.htm

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

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