Fingerprinting Lecture Notes

Comprehensive vocabulary flashcards covering friction ridge biology, surface interactions, classification patterns, development chemistry, and ACE-V forensic matching.

Ridgeology

The scientific study of friction ridges found on the epidermal surface of the skin.

Dactyloscopy

The scientific study and examination of fingerprints for identification purposes.

Friction Ridges

Elevated parts of the epidermis located on fingers, palms, soles of the feet, and lips that provide grip and sensory perception, becoming fully formed by $10\text{ weeks}$ of gestation.

Epidermis

The outermost, nerve-free and blood vessel-free layer of skin composed of $5$ distinct cell layers that migrate outward over $25\text{--}45\text{ days}$, with an outermost layer made almost entirely of keratin.

Papillary Layer

The uppermost layer of the dermis that provides nourishment to the epidermis, helps regulate temperature, and forms friction ridges.

Reticular Layer

The deeper layer of the dermis that imparts elasticity to the skin and houses nerve endings, hair roots, sebaceous glands, and sweat glands.

Hypodermis

The sub-dermal layer composed of collagen and fat cells that cushions against trauma, insulates the body, acts as an energy reservoir, and anchors the skin.

Thick Skin

Specialized skin located on the fingers, palms, and soles that lacks hair follicles and sebaceous (oil) pores, but contains friction ridges and sweat pores.

Porous Surface

A substrate material (such as paper, cardboard, or untreated wood) into which deposited fingerprint residues absorb.

Non-Porous Surface

A smooth substrate (such as glass, plastic, metal, or glossy paint) where deposited fingerprint residue remains sitting on the exterior surface, making it fragile and susceptible to damage.

Semi-Porous Surface

A substrate (such as glossy paper, wax paper, wallpaper, or matt paint) where a portion of the fingerprint residue is absorbed while the rest remains on the surface.

Patent Fingerprint

A clearly visible fingerprint formed when friction ridges deposit foreign substances such as paint, blood, or dirt onto a surface.

Latent Fingerprint

An invisible friction ridge impression formed by the transfer of perspiration and skin secretions, requiring physical, chemical, or optical processing to be seen.

Plastic Fingerprint

A clearly visible, three-dimensional friction ridge impression left in a malleable, soft medium such as clay, blood, or tar.

Loop

A fingerprint pattern class found in approximately $65\%$ of fingerprints, characterized by one or more ridges entering from one side, curving back, and exiting on the same side, containing exactly one delta and one core.

Radial Loop

A loop pattern whose ridges flow toward the radius bone, or the thumb side of the hand.

Ulnar Loop

A loop pattern whose ridges flow toward the ulnar bone, or the little finger side of the hand.

Delta

A characteristic Y-shaped ridge bifurcation or divergence of ridge lines that surround the central field of a fingerprint pattern.

Core

The focal center or approximate middle of a fingerprint pattern.

Whorl

A fingerprint pattern class present in approximately $30\%$ of prints, consisting of circular concentric or spiral ridge configurations with at least two deltas and one core.

Plain Whorl

A whorl pattern characterized by concentric circles or a spiral arrangement resembling a bullseye.

Central Pocket Loop Whorl

A whorl subtype that appears predominantly as a loop with a small whorl formation embedded at its center or end.

Double Loop Whorl

A pattern composed of two distinct loop formations colliding to create an S-shaped ridge design.

Accidental Loop Whorl

An irregular whorl pattern composed of a combination of two or more distinct pattern types.

Arch

A fingerprint pattern class observed in approximately $5\%$ of prints, characterized by ridges that enter from one side, rise centrally, and exit on the opposite side without forming a delta or a core.

Tented Arch

A sub-classification of arch pattern characterized by a sharp, steep central ridge rise rather than a gentle elevation.

Minutiae

Friction ridge detail features and discontinuities (such as endings, bifurcations, and dots) whose unique locations and types enable individualization.

Bifurcation

A minutia point at which a single continuous friction ridge diverges into two separate branches.

Enclosure (Lake)

A minutia structure formed when a single ridge splits into two, encircles a small area, and reunites into a single ridge.

Spur (Hook)

A minutia consisting of a short branch or notch protruding abruptly from a continuous friction ridge line.

Bridge (Crossover)

A short connecting ridge segment that runs between two longer parallel ridges.

Iodine Fuming

A chemical development technique where heated iodine crystals produce vapors that adhere to friction ridge deposits on porous and non-porous items, yielding a temporary reddish-brown ridge pattern.

Cyanoacrylate Fuming

A development method where superglue ($98\%$ cyanoacrylate) is heated to $80\text{--}120^{\circ}\text{C}$ in a humid environment to produce fumes that bind selectively to amino acids in latent residue on non-porous materials.

Ninhydrin

A chemical reagent sprayed or dipped onto porous materials that reacts with amino acid residues at $26\text{--}38^{\circ}\text{C}$ to generate a colored product termed Ruhemann's purple.

Small Particle Reagent (SPR)

A liquid suspension of fine molybdenum disulfide or zinc carbonate particles in detergent that binds to fatty deposits on non-porous and wet substrates.

Vacuum Metal Deposition (VMD)

A vacuum chamber method for non-metal surfaces in which evaporated gold penetrates into latent residue while subsequently evaporated zinc coats the background, leaving transparent print ridges against a white background.

Level 1 Detail

Overall friction ridge flow and pattern classification (arch, loop, whorl) capable of source exclusion but not individualization.

Level 2 Detail

Specific minutiae features (bifurcations, ridge endings, hooks, islands) and their spatial relationships used for personal individualization.

Level 3 Detail

Microscopic friction ridge attributes, such as sweat pore morphology, ridge widths, edge shapes, incipient ridges, and permanent scars.

ACE-V

A four-stage scientific protocol for friction ridge examination consisting of Analysis, Comparison, Evaluation, and Verification.