Fingerprints

History of Fingerprints

• Johann Christoph Andreas Mayer – 1788 • First scientist to recognize fingerprints were

unique

• William Herschel – 1856 • Began the collecting of fingerprints

• Alphonse Bertillon – 1879 • Created a way to identify criminals

History of Fingerprints

• Sir Francis Galton – 1888 • Developed the classification system for

fingerprints that is still in use today

• Ivan (Juan) Vucetich – 1891 • Improved fingerprint collection by adding all 10

fingerprint impressions

• Devised a system that divided fingerprint records into groups based on their pattern

What Are Fingerprints

• Fingerprints form on the fetus at 10 weeks

• All fingers, toes, feet, and palms are covered in small ridges

• When these ridges press against things they leave a mark

Classification of Fingerprints

• Three classifications – Loops – 65% of population

– Whorls – 30%

– Arches – 5%

LOOP WHORL ARCH

Loops

• Core – center of a loop

• Delta – triangular region located near a loop

• Enter from either the right or left and exit from the same side they enter (radial loop opens toward the thumb side, ulnar loop opens toward the pinkie side)

Whorls

• Look like a bulls-eye with two deltas (triangles)

• Divisions of whorls • Plain whorl – 24%

• Central pocket loop whorl – 2%

• Double loop whorl – 4%

• Accidental whorl – 0.01%

Plain Whorl

• Has one or more ridges that make a complete spiral

• Has two deltas; line drawn between them cuts at least one ridge in the inner pattern is touched or cut by the line`

Central Pocket Whorl

• Has one or more ridges that make a complete circle

• Has two deltas, line drawn between them does not touch any ridge in the inner pattern

Double Loop Whorl

• Has two separate loop formations and two deltas

Accidental Whorl

• Has two or more deltas and is a combination of two of the other patterns (but not the plain arch)

Arches

• Two different types of arches

– Plain arch – 4%

– Tented arch – 1%

Plain Arch

• Shows ridges entering one side, rising in the center and flowing out the other side without making an angle

• Has no characteristics of the loop pattern

Tented Arches

• Forms an angle, or it may possess some characteristics of the loop pattern, such as a delta

Fingerprint Identification

• Minutiae – the combination of details in the shapes and positions of ridges in fingerprints that make each unique

– these are also called ridge characteristics

– There are about 150 different ridge characteristics on an average fingerprint

Minutiae

Minutiae

• Endings – point at which a ridge stops

• Bifurcation – point at which one ridge divides into two

• Dots – very small ridges

• Islands – bigger than dots, occupy a middle space between two ridges

• Spur – a notch protruding from a ridge

• Bridge – small ridge joining two adjacent ridges

Legal Match

• In order to make a legal match, there must be 10 to 16 identical minutiae points on two prints

Types of Fingerprints at Crime Scenes

• Patent fingerprints – visible prints – Left on a smooth surface when blood, ink, or other

liquid comes in contact with the hands and is transferred to that surface

• Plastic fingerprints – actual indentations left in some soft materials like clay or wax

• Latent fingerprints – hidden prints – Caused by the transfer of oils and other body

secretions onto a surface

– Made visible by dusting with powders or by a chemical reaction

Fingerprint Forensic FAQ

• Can fingerprints be altered? NO • How reliable is fingerprinting as a means of

identification? – Only as reliable as the people performing the

testing. • How are fingerprints analyzed?

– In 1999, the FBI developed the Automated Fingerprint Identification System (AFIS)…takes ~ two hours to find a match if the person is in AFIS (47 million people are listed in AFIS

FAQ Continued

• How are latent fingerprints collected? – Surfaces are dusted with a fine carbon

powder that makes the print visible

– Tape is then used to lift and preserve the fingerprint

– The tape is placed on an evidence card, the date, time, location and collector are logged

– The fingerprints are also photographed prior to being lifted