Chapter 14

Fingerprints

Background Info. Bertillon’s system of anthropometry was

the 1st criminal identification method

It was used for 20 years, but the Will West situation proved it to be inaccurate

Chinese used fingerprints to sign documents 3,000 years ago!!

Important People

Henry Fauld (1880) Said that skin

ridge patterns could be used to identify criminals

He was ignored

Francis Galton (1892) Published Finger

Prints (1st book on the topic)

3 Patterns:

Loops Whorls Arches

Sir Edward Henry (1897)

Developed the classification system used today

The 3 Principles of Fingerprints

1. A fingerprint is an individual characteristic no two have identical ridge characteristics

**Ridge Characteristics (minutiae)**

Endings

Enclosures

Bifurcations (branching)

2. Fingerprints remain unchanged during a lifetime

Dermal papillae determine the form & pattern

Develop in the fetus & never change except to grow

Gangster

used acid to destroy his prints

unsuccessful

**John Dillinger**

3. Fingerprints have ridge patterns that are classified by:

Loops 60-65%

Whorls 30-35%

Arches 5%

Types of Ridge Patterns

1. Loops Ridge patterns that enter &

exit on the same side of the finger

A. Ulnar Loop loop comes from the little finger

B. Radial Loop comes from the thumb

2. Whorls Ridge patterns that are

somewhat circular in nature

A. Plain Whorls must have one ridge that makes a complete

circuit

spiral, oval, or circular

B. Central Pocket Loop same as above

C. Double Loop 2 loops in one print

D. Accidental contains 2 or more patterns

or a pattern not covered

3. Arches Ridge patterns that enter

on one side of the finger and exit

on the other

A. Plain Arch ridges rise in the center in a wave-like pattern

B. Tented Arch sharp rise

Primary Classification Based on Sir Henry’s original system

Look for the presence or absence of a WHORL

Each whorl gets a number value and then a ratio is set up

The Ratio

R. Index + R. Ring + L. Thumb + L. Middle + L. Little

R. Thumb R.Middle R. Little L. Index L. Ring

Number Values 1st Pair = 16 2nd Pair = 8 3rd Pair = 4 4th Pair = 2 5th Pair = 1 Arch/Loop = 0

*Now add 1 to both numerator & denominator = primary classification*

Detecting FingerprintsA. Latent Prints invisible

left by sweat & oils

B. Visible Prints left when fingers touch a colored substance blood, ink, paint

C. Plastic Prints impressions left on soft material

putty, wax, soap, dust

Developing Latent Fingerprints

A. On Non-absorbent and Hard Surfaces

Glass, mirrors, tile, plastic, etc.

1. Powders adhere to sweat & oil

2. Super Glue Fuming fumes stick to print & turn it

white

3. Reflected Ultraviolet Imaging System

RUVIS

Locates prints without powders or chemicals

B. On Porous and Soft Substances Paper, cardboard, cloth, etc.

1. Iodine Fuming sublimation of iodine (solid

gas)

produces fumes that react with print

short lived

2. Ninhydrin

reacts with amino acids in sweat

turns purple/blue

develops prints up to 15 years old

3. Physical Developer

last resort b/c it washes away proteins

silver nitrate based

develops prints on articles that were wet at one time

Preservation of Prints Photograph the print

Transport small objects with prints to crime lab protect with cellophane

Lift print with tape if on large or immovable objects

Digital Imaging Using computer software to enhance

a print

Adjusts color, brightness, & size

Compares 2 prints side-by-side & looks for common features