Classification of

Fingerprints

AFIS Automated Fingerprint Identification System

Fingers are scanned to a screen where they can be enhanced and identified.

In 2007 the FBI had more than 55 million digital fingerprints of known criminals.

AFIS Criminal courts

consider 12 points a “match” for prints

Known Print on File

Unknown Print

Types of Prints1. Plastic (Molded) Print

3D print made as indentations in soft material

Examples : fresh paint, soap, candle wax

Types of Prints2. Visible Print

left by a finger that has touched colored material

Examples: blood, paint, ink, grease, mud

Types of Prints3. Latent Print

prints result from deposit of secretions from skin

invisible to the naked eye until developed

developed by chemical or physical means

Visualizing Latent Prints

Powders used on hard, nonabsorbent surfaces adhere to both water and fatty deposits choose a color to contrast with the

background

Visualizing Latent Prints

Iodine fumes react with oils and fats to produce a

temporary yellow-brown color works best developing fingerprints on paper

or cardboard

Visualizing Latent Prints

Ninhydrin fumes reacts with amino acids to produce a

purple color works best developing fingerprints on

porous surfaces such as paper, wood, cardboard

Visualizing Latent Prints

Cyanoacrylate “superglue” fumes react with

water and other fingerprint constituents to form a hard, whitish deposit.

works best on developing fingerprints on hard nonporous surfaces such as metals, glass, and plastic