Environmental ScienceWildlife Forensics

Identifying Fingerprints

Why are fingerprints important evidence?

• Each person on the planet has a unique set of prints– Even identical twins have different patterns

• A fingerprint can prove:– A certain person was at the scene of a crime– They touched something that was used in a crime

History of fingerprinting

• Juan Vucetich: first used fingerprinting in criminal investigations– Anthropologist and police official in Argentina– 1891- he created first filing– 1892- made first positive ID of criminal• The murder of two children and stabbing of a mother• Mother survived, but latent print showed she was guilty

• Dr. Henry DeForrest: pioneered use of fingerprinting in U.S.– Civil service exam in New York– NY state prison system

What is a Fingerprint?

• Fingertips have small ridges and grooves that create a unique pattern– Their purpose is to create friction– These ridges form early in fetal development– Never change

• Skin is made of two layers– Outer epidermis

• Worn off and replaced throughout life

– Inner dermis• Holds oil and sweat glands to keep skin moist

– Oil transfers when you touch an object

Fingerprint Patterns• 3 Groups– Arches, Loops,

Whorls• Each group has a

different number of deltas

• Place where ridges converge from three sides to form a triangle

• Arches have none, Loops have one, and whorls have two

Arches• Simplest patterns and have no deltas• Plain Arch

– Moves across finger with no center point (core) or intersecting ridges

• Tented Arch– The center core looks like a pole holding up a tent– NOT a delta

Loops• The most common print pattern• Ridges enter/exit from same side• One delta• If you know which hand the print is from, you

can determine radial or ulnar loop

Whorls

• 4 different types:– Plain whorl: looks like a

ripple effect in water– Central pocket whorl:

smaller center circles, outer ridges move to one side (loop-like)

– Double loop whorl: Two separate loops wrapped together

– Accidental whorl: very uncommon, combination of different loop and whorl patterns

• The center of a whorl looks like a circle• Have two or more deltas

Fingerprint Evidence• 3 Types of fingerprint evidence– Describe the surface the print was made on and how

the print was made– 1) Latent print: mark left on a surface from the finger’s

natural oil• Not clearly visible until another material reacts with oils• Most common method is dusting

– 2) Visible print: made when fingertip is covered with some substance and leaves a mark • Can be seen without help from other materials

– 3) Plastic impression: 3-D print made when finger is pressed into soft material that holds its shape• Clay, putty, grease, wet paint, wax, etc.