Fingerprints

Fingerprints as a Forensic Tool

• Fingerprints as a means of identification has been around as long as 3000 years ago

• Used forensically since start of 20th century

• Every single individual has a unique and unchangeable fingerprint

• AFIS or IAFIS• Integrated automated

fingerprint identification system has revolutionized fingerprint technology as a forensic tool

• Fingers, palms, and soles of feet have friction ridges formed in womb

• Sweat and oils are deposited on surfaces the fingers touch.

Fingerprints

1. Have subject relaxed and comfortable

2. Be sure subject’s hands are clean and dry

3. Grasp the individual's right hand at the base of the thumb with your right hand. Cup your hand over the individual's fingers, tucking under those fingers not being printed

Guide the finger being printed with your left hand.

4. Roll the finger on the inking pad so that the entire fingerprint pattern area is evenly covered with ink.

Taking Fingerprints

5. In taking the rolled impression, the side of the bulb of the finger is placed upon the paper fingerprint card and the finger is rolled to the other side until it faces the opposite direction. Care should be exercised so the bulb of each finger is rolled evenly from tip to below the first joint.

• Fingerprint Rolling Technique

Generally, the weight of the finger is all the pressure needed to clearly record the fingerprint.

Notes: On Fingerprint collection• Roll toward center of

body• Do not let go of an

individual once fingerprinting has started on a particular hand

• Special situations: http://www.fbi.gov/hq/cjisd/takingfps.html

• After rolled fingerprints are obtained, get plain impressions at the bottomof the card. Simultaneouslypress the individual's four fingers keeping the fingers together, on the surface of the fingerprint card at a forty-five degree angle in order to capture all four fingers in the allotted space Print both thumbs simultaneously in the plain impression thumb blocks (to ensure that they are in the proper spaces).

Quality

• Make sure all prints have been taken and they are in the correct order

• Verify that the finger has been fully rolled– If the fingerprint impression

is a loop, are the delta and core present?- If the fingerprint impression is a whorl, are all deltas present?

Quality

• Are the fingerprint impressions uniform in tone and not too dark or light?

Classification of Fingerprints

• Ridge patterns: arches (left), loops (center), and whorls (right)

• 60-65% population has loops• 30-35% population has whorls• 5% population has arches

Loops

• All loops must have one delta

• Radial loops open toward thumb

• Ulnar loops open toward pinky

• Where is the delta here?

Whorls

• Must have a minimum of two deltas

• Four sub-categories of whorls

• Where are the deltas here?

Arches

• Do not have deltas• Ridge enters on one side of fingerprint and exits

on other side• Tented arch has sharp upthrust instead of

smooth

Arch Tented arch

Minutia

• This is what individualizes a fingerprint

• See handout• 8 points of minutia

standard for positive identification

• Some states as little as 5 others as many as 12

Identifying your Fingerprint Type

• Blow balloon up to stretch it• Let air out• Blow balloon up to about 1 inch, DO NOT TIE IT

OFF• Ink fingerprint• Roll finger on balloon• Blow balloon up to about 3-4 inches DO NOT

TIE UNTIL YOU ARE SATISFIED YOU HAVE A DECENT PRINT

• Identify general classification and minutiae with marker