Environmental Science Wildlife 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 – he created first filing – 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.