Dactyloscopy the study of fingerprints Fingerprints are useful

Dactyloscopy …the study of fingerprints

Fingerprints are useful because… • they’re unique • they’re consistent over a person’s lifetime • we have a systematic classification scheme Why do we even have these ridge patterns? • provide a better grip? (friction ridges) • make perspiration easier on a hairless surface? • improve our sense of touch? Apes and monkeys also have them on fingers and toes

Can also be found on your palms, feet, and lips They are NOT genetically controlled…even identical twins have different fingerprints! Sweat pores along ridges release perspiration made up of 99% water. After evaporation, the remaining residue consists of salts, organic compounds, and body oils.

3 Basic Patterns: 1. Loop; at least one ridge enters and leaves from the same side a. Radial loop opens to radius bone (thumb side) b. Ulnar loop opens to ulna bone (pinky side) Contain a core and a delta

3 Basic Patterns: 2. Whorl; at least two deltas and a core 4 types: a. Plain whorl b. Central pocket c. Double d. Accidental

3 Basic Patterns: 3. Arch; ridges enter on one side and exit on the other (usually no delta or core) Types; a. Plain b. Tented

60% Ulnar loop Plain arch 20% Plain whorl Other whorls 10% Other whorls Ulnar loop 5% Radial loop Tented arch 4% Plain arch Radial loop 1% Tented arch Plain whorl

Henry Classification System Looking for whorls!!! R. Index R. Ring L. Thumb L. Middle L. Little ------ ------ R. Thumb R. Middle R. Little L. Index L. Ring 16 8 4 2 1

Right Index Right Ring + ------ + Right Thumb Left Thumb + ------ + Right Middle Left Middle + ------ + Right Little Left Little + ------ + Left Index Added Automatically Left Ring 1 ------ + FINAL GROUP = ------ 1 Added Automatically FINAL GROUP

Ridge Classification Individual ridge characteristics are called minutiae. No legal requirements in the US regarding the number of points that must match before deciding that a fingerprint belongs to a certain individual. Criminal courts generally accept 8 -12 points of similarity.

Types of Fingerprints Plastic; indented or molded prints made by pressing a finger into a plastic-like material

Visible; from a finger that has touched colored material such as blood, ink, paint, mud, dust, etc.

Latent prints; made by the deposit of perspiration or body oils. These prints are invisible to the naked eye until “developed” by some chemical or physical means.

Visualizing Latent Prints “Dusting” for prints; • Use fine powder that adheres to body oils and perspiration • Use a powder that contrasts with the surface (ex. Use white powder on a dark surface and black powder on a light surface) • Brush away excess powder that does not adhere to the print • “Lift” the print with clear, sticky tape • Works best on hard, non-absorbent surfaces

DUSTING FOR PRINTS VIDEO Developing prints with superglue video