Unit 3: Fingerprints (part 2)

A. Three basic patterns—loops, whorls, and arches

II. Classification of fingerprints:

Loop

Whorl Arch

1. Loop 

a. = one or more ridges entering from one side, curving, then going out from same side entered

 b. contains a delta and a core

 c. ~ 65% of all fingerprints have loops

d. Subcategories of loop 

i. Radial loop = opens toward the thumb, which is toward the radius

 ii. Ulnar loop = opens toward the little finger, which is toward the ulna

 (NOTE: need to know which hand print came from to determine radial or ulnar loop . . . ulnar loops are more common)

Ridges flow in the Ridges flow in the directiondirection of the thumb of the little finger

Radial Loop Ulnar Loop

Left Hand Right Hand

Fingerprint Techniques Manual, page 13--New Mexico Department of Health--http://dhi.health.state.nm.us/elibrary/cchspmanual/fingerprint_manual.pdf

2. Whorls

a. = contains at least two deltas and a core

b. ~ 20% of fingerprints are plain whorls, ~ 10% are composite or accidental whorls

 c. Subcategories of whorl

 i. plain whorl

 ii. central pocket loop whorl

iii. double loop whorl

iv. accidental whorl

WhorlsWhorls have at least one ridge that makes (or tends to make) a complete circuit. They also have at least two deltas. If a print has more than two deltas, it is most likely an accidental.

Draw a line between the two deltas in the plain and central pocket whorls. If some of the curved ridges touch the line, it is a plain whorl. If none of the center core touches the line, it is a central pocket whorl.

Plain Whorl

Central Pocket Whorl

This slide: http://sciencespot.net/Pages/classforsci.html#fiingerprint

3. Arches 

a. = all ridges enter on one side and exit on the other

 b. contain NO delta or core

 c. least common

 d. Subcategories of arch

 i. plain arch

 ii. tented arch

Fingerprint Techniques Manual, page 9--New Mexico Department of Health--http://dhi.health.state.nm.us/elibrary/cchspmanual/fingerprint_manual.pdf

Fingerprint Techniques Manual, page 8--New Mexico Department of Health--http://dhi.health.state.nm.us/elibrary/cchspmanual/fingerprint_manual.pdf

B. Ridge classification (Individualization) 1. Minutiae = fine structure of ridge characteristics include . . .

 ridge ending  bifurcation dot

 

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

core delta

island (enclosure)

short ridge

AFIS and IAFIS

The computer database uses minutiae to compare fingerprints and determine a

match.

Identify Minutiae

Circle using the Promethean pen

http://ridgesandfurrows.homestead.com/pictures.html

Just for Fun

Extra Resources http://dhi.health.state.nm.us/elibrary/cchspmanual/finger

print_manual.pdf

Quick Tips If a fingerprint has no deltas, it is an arch. If a fingerprint has one delta, it is a loop. If a fingerprint has two or more deltas, it is a whorl.

It’s time to take some prints!

Info on slide: http://sciencespot.net/Pages/classforsci.html#fiingerprint

Click image for FBI instructions on taking fingerprints

Image from: http://www.staffs.ac.uk/schools/sciences/forensic/policing_and_criminal_investigation/taking_prints.jpg