Fingerprinting

Patent Prints

Made after finger comes in contract with visible material (Blood, ink, grease paint)

Plastic Prints

Indented visible impressions left in soft material (Clay, wax, vaseline)

Latent Prints

Invisible prints that must be processed to be seen (Sweat)

Level 1 Classification of Prints

Includes major fingerprint patterns

The core

Approximate center of pattern

Type lines

Diverging ridges that surround the core

The Delta/s

Triangular shaped area where type lines meet

Arch

Have ridges that enter on one side, rise, and exits on the other side. About 5% of fingerprints

Loops

At least one ridge enters on a side, curves, and exits on that same side. 60-65% of fingerprints. 1 Delta and 1 Core

Whorls

Have ridge patterns that are generally rounded or circular in shape and have a MINIMUM of two deltas. 30-35% of fingerprints. 2 Deltas and 1 Core

Plain Arch

Ridges start on one side, rise in the middle and exit on the other side. No core or deltas. ~5% of all fingerprints

Tented Arch

Ridges start on left, sharp rise in the middle and exist on the right. Angle <90 degrees

Plain Loop

Ridges start on one side, loop around, and leave on the same side

Ulnar loop (right)

Opens towards the pinkie

Radial Loop (left)

Opens towards the thumb. Most often index finger

Whorl

Circular pattern radiating around the center of the finger. Two or more deltas

Plain Whorl

Line between deltas crosses circular part of ridge pattern

Central Pocket Loop Whorl

Line between deltas does not cross circular part of ridge pattern

Double Loop Whorl

Two opposing loops side by side

Accidental Whorl

Combination of any two patterns except Plain Arch

Level 2 Fingerprint Characteristics

Individual Ridge Characteristics (Minutiae)

Ending ridges

A single ridge comes to an end

Bifurcations

A ridge splits to form 2 adjacent, roughly parallel ridges

Ridge islands

Dots, islands

Minimum number of minutiae for ID

No standard, usually 8-16. The more the better! 14-16 matches are required for identity in English courts

Level 3 Fingerprint Details

Extremely tiny features of the friction ridges. Includes shape of ridge edges, width of ridges, shape and relative locations of pores along the ridges. Difficult to see in most latent fingerprints, easily obliterated.

Qualitative/Quantitative Process

Inverse relationship. The more quantity of detail that can be matched, the less clear the print has to be, and vice versa

ACE-V (Ridgeology)

Analysis, comparison, evaluation, and verification

Conclusions

Source identification, inconclusive, source exclusion

Latent Prints

Try to visualize by non-destructive means first. (White light, episcopic coaxial illumination, ultraviolet illumination, lasers and alternative light sources)

Physical Development

Usually for hard, non porous surfaces (glass, metal, plastic, guns)

Chemical

Usually used for porous surfaces: paper/pape-like

Sequential

Increase contrast. Dark background - make print lighter and vice versa

Small particle reagent

Used for hard surfaces that are wet or have previously been wet. Particles are sprayed with a reagent

Iodine Fuming

Useful for prints on porous surfaces, unstable and must be photographed to be preserved, prints must be fixed with starch. Method is rare due to toxicity

Ninhydrin

Reacts with amino acids to yield a bluish-purple color. Reacts slowly and must be accelerated by heat and moisture. Very effective, works on paper as old as 15 years

AFIS

Automated Fingerprint Identification Systems

AFIS

Scanning devices convert fingerprints to digital images and finds matches. FINAL DECISIONS ARE MADE BY EXAMINER