Forensic Science 1-Fingerprint Analysis-University of Southern Mississippi

Fingerprint Analysis Includes

Known fingerprints, unknown fingerprints, ACE-V methodology, and AFIS systems.

Forensic and Criminal Justice Uses

Identification: Criminal offenders, decedents.

Physical Evidence: Common, versatile, multiple processing techniques available.

Skin as an Organ

The largest organ of the body.

Friction Ridge Skin

Specialized skin found on the palmar surfaces (hands) and plantar surfaces (feet); hairless and contains the highest concentration of sweat glands.

Fingerprint (Definition)

Any impression or reproduction left by friction ridge skin.

Known Fingerprints (Exemplars)

Prints deliberately recorded from an identified individual for comparison purposes; provide a complete record of friction ridge skin.

First Principle — Permanence

Friction ridge patterns form in fetal life and remain unchanged throughout life and after death, except for permanent scarring.

Second Principle — Uniqueness

Friction ridge patterns are unique to each individual and finger, even in identical twins.

Levels of Detail in Fingerprints

Level 1: Ridge flow (pattern types).

Level 2: Ridge path (minutiae).

Level 3: Ridge shape (edges and pores).

Major Fingerprint Pattern Types

Arch (5%), Loop (60-65%), Whorl (30-35%).

Arch Subtypes

Plain arch, tented arch.

Loop Subtypes

Ulnar loop: Opens toward ulna (pinkie side).

Radial loop: Opens toward radius (thumb side).

Whorl

Circular or spiral ridge pattern; may include plain, central pocket, double loop, or accidental whorls.

Minutiae

Small ridge characteristics such as ridge endings, bifurcations, and dots; crucial for individualization

Ridge Shape

Fine detail features like ridge edges, contours, and pore positions—used in high-resolution analysis.

Source of Fingerprint Uniqueness

Determined by the number, location, and spatial relationship of minutiae.

Definition of Unknown Fingerprint

Partial reproduction of friction ridge skin left on an object by chance.

Types of Unknown Prints

Latent: Invisible; left by oils or perspiration.

Patent: Visible; left in substances like blood, grease, or mud.

Plastic: 3D impression in a pliable surface (e.g., wax, soap).

Factors Affecting Processing

Type of print, surface (porous/non-porous), available resources, and order of operations.

Processing Categories

Optical: Photography.

Physical: Powders adhere to residue.

Chemical: Reactions (superglue fuming, dye stains).

What Fingerprints Can Show

That a person touched an item.

What Fingerprints Cannot Show

How, when, or how long ago an item was touched.

Age, gender, or race of the person.

Note: The absence of prints ≠ proof that an item wasn’t touched.

What ACE-V Stands For

Analysis, Comparison, Evaluation, Verification.

Analysis Step

Examiner assesses print quality and conditions (substrate, medium, pressure, motion, clarity, anatomical area). Determines if sufficient for comparison.

Comparison Step

Direct side-by-side assessment between known and unknown prints, using known suspects or databases; must fall within acceptable variation limits.

Evaluation Step

Examiner reaches one of three conclusions:

Identification: Same source.

Exclusion: Different sources.

Inconclusive: Insufficient detail.

Verification Step

Independent review by another qualified examiner; procedure varies by agency or department policy.

AFIS Definition

Computerized system for storing, searching, and comparing fingerprint records at local, state, and federal levels.

Known Database in AFIS

Stores electronic fingerprint and palm print exemplars; system automatically extracts minutiae.

Latent Database in AFIS

Examiner manually plots minutiae from unknown prints for searching.

AFIS Search Types

Blind Search: Latent print searched against entire database.

Direct Search: Latent compared to one specific person’s known prints.

Reverse Search: Known prints searched against all unidentified latents.

AFIS Limitation

AFIS suggests possible matches but does not identify suspects—human examiners make the final determination.

Importance of Quality Data

"Garbage in = garbage out" — accurate, high-quality known prints are essential for reliable AFIS results.