fingerprinting forensics 352. fundamental principles of fingerprints a fingerprint is an individual...
TRANSCRIPT
Fundamental Principles of Fingerprints
• A fingerprint is an individual characteristic.
• A fingerprint remains unchanged during an individual’s lifetime.
• Fingerprints have general characteristic ridge patterns that permit them to be systematically classified.
Anatomy of Fingerprints
• Will two people ever have the same fingerprints?– No two people have the same ridge
characteristics…even identical twins!!!• Where can ridges be found?
– Ridges can be found on you palms, feet, and lips.
Anatomy of Fingerprints
• Skin is composed of an epidermal outer layer and a dermal inner layer.
• In between the epidermis and the dermis, finger-like papillae press into the epidermis causing friction ridges.
Anatomy of Fingerprints
• When the ridges press against objects, they leave an impression.
• The impression consists of natural secretions of the sweat glands.
• The secretions are a combination of water, oils, salt, and dirt.
Fingerprint Basics
• The core is the center of a fingerprint.• A delta is triangular area found on a
fingerprint.
Categories of Fingerprints• A loop must have one or more
ridges entering and exiting from the same side. Loops must have one delta.
• Subcategories
– Radial : opens toward the thumb
– Ulnar : opens toward the “pinky” (little finger)
• Which type of loop is this, if it is on the right hand? Left hand?
1. Loop (65%)
Categories of Fingerprints• Whorls have at least two deltas
and a core. • Subcategories
– Plain: at least one ridge makes a complete circuit
– Central pocket: no recurving ridge is touched in the pattern
– Double loop: made of two loops
– Accidental: a pattern not covered by other categories
2. Whorl (30%)
Categories of Fingerprints
2. Whorl (cont.)Distinguish between Plain and Central Pocket Loop• Draw in the pattern, which is a line between the
two deltas.
If the pattern line loops and touches the line twice - Plain
If the pattern line loops and does not touch the line - Central Pocket Loop
Categories of Fingerprints
3. Arch (5%) • Arches have ridges that enter on one side of the finger and cross to the other side while rising upward in the middle.
• They do NOT have deltas or cores.
Subcategories
Plain
Tented
Ridge Characteristics
• Fingerprint analysis is done by careful study of ridge characteristics also called minutiae.