Fingerprints

Discovered that they are unique. No 2 alike.

A classification system was developed.LoopsWhorlsArches

Reasons they became useful

Computer databaseAFIS Automated Fingerprint Identification

System1990

IAFIS Integrated Automated Fingerprint Identification SystemCriminal histories; mug shots; scars and tattoo

photos; physical characteristics like height, weight, and hair and eye color; and aliases.

Response time:10 minutes for electronically submitted criminal prints.One hour for electronically submitted civil prints.

Classification

Loop – comes in one side and out that same side. One delta on the side opposite from where it starts and exits. Most common

Patterns

DeltaEnter

Exit

Turn

Whorl – Circular shape. Two deltas on either side.

Patterns

DeltaDelta

Arch – Up thrust, with a decline. Exits opposite side.

Patterns

Enter Exit

Up Thrust

Plastic – finger contacts a soft surface such as putty.

Visible. Finger is covered with a liquid such as blood and then contacts a hard surface.

Latent – Invisible. Oils, salts and other debris stick to a surface when it is touched by a finger. Most common.

Types of fingerprints at crime scene

Lighting – flash light, etc.

Chemical reactionIodine mixes with starches in the fingerprint

and turns brownNinhydrin mixes with the amino acids in the

fingerprints and turns purple.

Methods to search for fingerprints

Dusting with fingerprint powderGray – aluminum dustBlack – carbon or charcoal

Ultraviolet image converter – Reflected Ultraviolet Imaging System (RUVIS)

Iodine FumingNot permanentMust be photographed

Methods to enhance a fingerprint

Ninhydrin Amino acidsTurns purple within an hour or two.

Physical developerSilver nitrate based liquid reagentGood for porous surfaces

Methods to enhance a fingerprintCont.

Used for slick surfaces.

Superglue and dusting.

Combination methods

Identifying the pattern (loop, whorl, arch)

Looking for minutiaeRidge endingBifurcationIslandCoreDeltaCicatrix

Steps in identifying a fingerprint

What do you compare a lifted print to?A known sample

How many points does the FBI use in identifying a print?14

How does a fingerprint match become confirmed?With a microscopic match by a human being.

Questions