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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
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