Fingerprint Analysis: Minutiae, Classification, and Detection Methods

Ridge Characteristics (Minutiae)

Points where ridges end, split, or come together; the unique details of a fingerprint.

How many identical ridge characteristics can two people share?

Up to 8, but no two people have more than 8 in common.

When are fingerprints formed?

During fetal development when the dermal papillae form.

Why do fingerprints stay unchanged?

Because the dermal papillae structure never changes throughout life.

Where do oils in fingerprints come from?

Sweat glands + oils picked up by touching hairy parts of the body.

Patent Print

Visible print made by a substance like blood, paint, or ink.

Plastic Print

3D impression left in a soft material like wax or clay.

Latent Print

Invisible print made by sweat and oils; must be developed.

Minutiae

Ridge characteristics used to identify fingerprints (endings, bifurcations, etc).

Probability of two identical fingerprints

Extremely small; millions of prints classified, none identical.

AFIS

A computer system that scans, digitizes, and compares fingerprints at high speed.

Porous Surface Examples

Paper, cardboard, untreated wood.

Nonporous Surface Examples

Glass, metal, plastic.

Best method for prints on porous surfaces

Chemical methods (ninhydrin, iodine fuming).

Best method for prints on nonporous surfaces

Powder dusting or superglue fuming.

Dusting

Applying powder to reveal prints on nonporous surfaces.

Superglue Fuming

Vapor from cyanoacrylate forms a white print on nonporous surfaces.

Ninhydrin

Chemical used on porous surfaces; prints turn purple-blue.

Iodine Fuming

Vapor sticks to oils; prints appear brown but temporary.

RUVIS

Reflected UV Imaging System; detects latent prints using UV light.

Light Sources

UV or alternate light used to reveal or enhance fingerprints.

Three main fingerprint classes

Loops, whorls, arches.

Loop

Ridge enters and exits same side; has one delta.

Ulnar Loop

Loop opens toward the pinky.

Radial Loop

Loop opens toward the thumb.

Whorl

At least one ridge makes a complete circuit. has two deltas

Arch

Ridges enter one side and exit the other; no deltas or cores.

Percentage of Loops

60-65%.

Percentage of Whorls

30-35%.

Percentage of Arches

5%.

Partial Prints

Incomplete fingerprints that still may contain enough minutiae to identify someone.

Digital Fingerprinting

Electronic scanning and storing of fingerprints for faster comparison.

Bertillon System

Early identification system based on body measurements (anthropometry).

Galton's Contribution

Published Fingerprints (1892), establishing modern fingerprint science.

Will West Case

Showed Bertillon's system failed; fingerprints proved individuality.

Fundamental Principle #1

No two people have identical fingerprints.

Fundamental Principle #2

Fingerprints remain unchanged throughout life.

Fundamental Principle #3

Fingerprints can be systematically classified by patterns.