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.

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

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

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

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

R. IndexR. RingL. ThumbL. MiddleL. Little R. ThumbR. MiddleR. LittleL. IndexL. Ring

Right Index Right Ri ng Left Thumb Left Middle Left Little Added Automatically FINAL GROUP = Right Thumb Right Middle Right Little Left Index Left Ring Added Automatically FINAL GROUP

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.

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.

“ 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