Fingerprint Classification

Classifying PrintsWhy 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) - 1899• 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 Index16

Right Ring8

Left Thumb4

Left Middle2

Left Little1

Right Thumb16

Right Middle8

Right Little4

Left Index2

LeftRing1

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