Chapter 14 Fingerprints

Background Info. Bertillon’s system of anthropometry was the 1 st 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 (1 st 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 1 st Pair = 16 2 nd Pair = 8 3 rd Pair = 4 4 th Pair = 2 5 th Pair = 1 Arch/Loop = 0 *Now add 1 to both numerator & denominator = primary classification*

Detecting Fingerprints A. 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