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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