Fingerprint Classification

Classifying Prints Why classify prints? To add order to chaos – like a library organizing books by author or subject matter. Fingerprints are only useful if they can be searched quickly for a match. How are prints classified (grouped)? By arches, loops, whorls – each person has a different number of these types of patterns Everyone has these, but HOW people have them is unique

Arches Ridgelines that rise in the center to create a wave- like pattern Types: Plain, Tented 5% of all pattern types

Loops One or more ridges that double back on themselves. Types: Radial, Ulnar – Categorized by how they flow – Radial: Flow down, toward the radius (thumb side) – Left Loop – Ulnar: Flow toward the ulna (little finger) – Right Loop 60% of pattern types

Loops (Right Loop – coming from the right)(Left Loop – coming from the left)

Whorls “Whirlpools” of ridgelines Types: – Plain: concentric circles (“bulls eye”) – Central pocket: Loop with whorl at the end – Double: two loops that collide – S shape pattern – Accidental: whorls that are different from each other and are irregular 35% of pattern types

Whorls

Individual Ridge Characteristics

Henry Classification System Sir Edward Henry (British police) Prints are assigned a score based on where whorls show up within a ten-finger set of prints. Total score is used to narrow down matches into all sets with same scores (1,024 different groups). Totals Right Index 16 Right Ring 8 Left Thumb 4 Left Middle 2 Left Little 1 Right Thumb 16 Right Middle 8 Right Little 4 Left Index 2 Left Ring 1

AFIS Automated Fingerprint Identification System Scanning and digital encoding of fingerprints Searches 500,000 prints per second! Once a match is found, an agent hand-checks the file(s) Problem: Many AFIS systems exist are not compatible

Types of fingerprints Patent Plastic Latent

Powdering Prints

Chemistry with Prints Cyanoacrylate Vapor Iodine Fuming Ninhydrin Silver nitrate

Digital Fingerprinting