Forensic Science: Fingerprint Identification and Analysis

Comprehensive vocabulary flashcards covering the core forensic principles of fingerprints, anatomical skin layers, minutiae details, pattern classifications, the ACE-V identification methodology, visualization methods, and identification databases (AFIS and NGI).

Fingerprints

A copy of the skin ridges found on the palm side of the fingers.

Three Basic Principles of Fingerprints

1. A fingerprint is an individual characteristic (no two fingers have the same patterns)

2. A fingerprint will not change in someone's lifetime

3. Fingerprints have shapes (loops, whorls, arches) that allow them to be sorted and searched in a database.

Loops

Fingerprint patterns that must have one or more ridges entering from the same side, curving around (like a U-turn), and leaving the same side;

they must possess at least one delta and occur in $60\text{--}65\%$ of the population.

Delta

A triangular shape formed where skin ridges split apart in different directions.

Whorls

Fingerprint patterns characterized by a circle in the center and at least two deltas, occasionally appearing as a double whorl resembling a yin and yang

found in $30\text{--}35\%$ of the population.

Plain Whorl vs. Central Pocket Loop

A classification distinction made by drawing a line between the two deltas: if the line touches or crosses the inner circle, it is a Plain Whorl; if the line misses the inner circle completely, it is a Central Pocket Loop.

Arches

Fingerprint patterns formed by ridges entering from one side, rising and falling like a hill, and exiting on the opposite side, containing no type lines, deltas, or cores

found in $5\%$ of the population.

Class Characteristic (Fingerprints)

The general overall pattern or shape of a print (Loops, Whorls, or Arches).

Individual Characteristic (Fingerprints)

Specific ridge characteristics (minutiae) unique to a single person, such as bifurcations, ridge endings, and dots.

Epidermis

The outer layer of the skin.

Dermis

The inner layer of the skin.

Dermal Papillae

The middle layer of cells between the epidermis and dermis that forms during fetal development and determines the fingerprint pattern.

ACE-V

The four-step scientific method used to identify fingerprints:

Analysis (observe print usability)

Comparison (compare crime scene print to suspect print)

Evaluation (determine match)

and Verification (confirmation by a second examiner).

Three Levels of Comparison (ACE-V)

Level 1: General shape and ridge flow (loops, whorls, arches);

Level 2: Specific ridge characteristics or minutiae (splits and endings);

Level 3: Microscopic details (sweat pores, tiny scars, breaks, and creases).

Visible Prints

Patent crime scene fingerprints created when fingers touch a surface after ridges have been in contact with a colored material such as blood, paint, dirt, or ink.

Plastic Prints

Three-dimensional ridge impressions left in soft materials, such as putty, wax, soap, or dust.

Latent Prints

Invisible fingerprint impressions transferred onto a surface by clear bodily oils and perspiration present on the fingertips.

Bifurcation

A fingerprint minutia point where a single ridge line splits into two separate lines, taking the shape of a Y.

Ridge Ending

A fingerprint minutia point where a single ridge line comes to an abrupt dead end.

Enclosure

A fingerprint ridge minutia where a single ridge divides into two branches and then rejoins, forming an enclosed circle or oval space.

Ridge Island

A microscopic, dot-like ridge segment that stands completely isolated by itself between two parallel ridge lines.

Latent Print Visualization Methods

Chemical and physical development techniques that include

fingerprint powders

iodine fuming (turns brown)

ninhydrin (turns purple)

superglue fuming (vapor hardens into a white permanent print),

and ALS (laser or Alternate Light Sources).

Latent Print Preservation

The standard chain of processing prints by photographing first, performing tape lifting, and securing items in a paper envelope or box.

AFIS (Automated Fingerprint Identification System)

A digital biometric system that converts the locations of minutiae into algorithmic code to scan databases at high speed and present candidate matches for manual expert verification.

NGI (Next Generation Identification)

The FBI's biometric repository replacing IAFIS; i

t features four primary biometric modalities (fingerprints, palm prints, facial recognition, and iris scans) with a $99.6\%$ match accuracy.

RISC

A mobile search system integrated within the FBI's NGI system capable of returning rapid identification query results in under $10\text{ seconds}$.