FORENSICS MIDTERM REVIEW (Units 1-4)

Trace Evidence

Small, often microscopic material found at a crime scene or on a victim/suspect.

Locard's Exchange Principle

The concept that when two objects come into contact, there is always an exchange of materials.

Class Characteristic

Property of evidence that can only be associated with a group and never a single source.

Individual Characteristic

Property of evidence that can be attributed to a common source with an extremely high degree of certainty.

Comparison Microscope

Two compound microscopes connected by an optical bridge, allowing two samples to be viewed side-by-side.

Keratin

The main protein composition of hair.

Follicle

The structure from which the hair grows.

Cuticle

The outer protective layer of hair, composed of overlapping scales.

Cortex

The intermediate layer of hair, composed of elongated cells, containing pigment (melanin).

Medulla

The central core of the hair shaft (may be continuous, interrupted, fragmented, or absent).

Medullary Index (MI)

The ratio of the medulla diameter to the hair shaft diameter (MI < 1/3 for human hair, MI > 1/2 for animal hair).

Anagen Phase

The initial growth phase where the hair follicle is actively producing hair.

Telogen Phase

The final resting phase before the hair is shed.

Root/Follicular Tag

Tissue adhering to the root of the hair, often containing mitochondrial DNA (or nuclear DNA if the entire root is present).

Natural Fiber

Fiber derived entirely from animal or plant sources (e.g., cotton, wool, silk, linen).

Manufactured/Synthetic Fiber

Fiber derived from natural or synthetic polymers (e.g., rayon, nylon, polyester, acrylic).

Polymer

A substance composed of long chains of repeating molecular units (monomers).

Birefringence

A double refraction characteristic of some fibers, examined under polarized light to distinguish between different types.

Striation

A scratch mark or series of lines left by the passing of a tool across a surface.

Impression/Indentation

A negative print or mark left when a tool is pressed into a softer material.

Lands and Grooves

The internal components of a gun barrel that impart twist/spin to a projectile; rifling (analogous terms for toolmarks).

Comparison (Forensic)

The process of matching unique marks on a piece of evidence (like a bullet, toolmark, or fingerprint) to a known source.

Binder

The non-volatile portion of paint that forms the film; provides adhesion and durability.

Pigment

Fine powder material that gives paint its color and opacity.

Solvent

The liquid medium that dissolves or disperses the binder and pigment.

Layer Structure

The unique sequence and composition of paint layers, especially in automotive paint.

Amorphous Solid

A solid in which the atoms and molecules are arranged in a random manner, not a crystal structure (like glass).

Refractive Index (RI)

The ratio of the velocity of light in a vacuum to its velocity in a specified medium (a method of characterizing glass).

Becke Line

A bright halo observed near the border of a particle immersed in a liquid of different refractive index; used to determine RI.

Radial Fracture

Cracks that radiate outward from the point of impact (on the opposite side of the impact).

Concentric Fracture

Cracks that form in a rough circle around the point of impact (on the same side as the impact).

Tempered Glass

Glass that is rapidly cooled during manufacturing, causing it to fragment into small, blunt pieces when broken.

Wallner Lines

Stress markings on the edge of broken glass fragments; they can help determine the direction of force.

Accidental Whorl

A whorl that kinda looks like a bean

Apocrine Gland

A type of gland that secretes sweat, ex. armpits

Arch

A fingerprint pattern that has no deltas.

Loop

A fingerprint pattern that has one delta.

Bifurcation

A type of minutiae where a ridge splits into two.

Biometric Identifiers

Unique physical characteristics used for identification. (pretty much just minutiae)

Central Pocket Whorl

A type of whorl fingerprint with a circle or dot in the center

Class Characteristic

A characteristic that can only be specified to a group, never an individual

Core

The center of a fingerprint pattern.

Delta

A point on a fingerprint where ridges diverge.

Dot

A small fingerprint minutiae.

Double-Loop Whorl

A fingerprint pattern that consists of two loops.

Eccrine Gland

A type of gland that produces sweat for thermoregulation.

Friction Ridge Skin

Skin that has raised ridges used for gripping. Tends to be on palms of hands and soles of feet, probably only need to focus on palms of hands

Henry System (Henry Classification System)

A method for classifying fingerprints. its weird just watch a video to understand u got this

Individualization

The process of identifying a unique fingerprint.

Interoperability

The ability of different systems to work together.

Iodine Fuming

A technique used to visualize latent fingerprints.

Latent Print

A fingerprint that is not visible to the naked eye/ A hidden fingerprint

Magna Brush

A tool used for dusting fingerprints.

Minutiae

Unique features of a fingerprint that aid in identification.

Ninhydrin

A chemical used to visualize latent fingerprints.

Patent Print

A visible print

Physical Developer

A chemical used to develop latent fingerprints.

Plastic Print

A three-dimensional fingerprint, embedded in something

Powder Dusting

A method for revealing latent fingerprints using powder.

Radial Loop

A loop fingerprint that opens toward the thumb.

Random Match Probability

The likelihood that a fingerprint matches by chance.

Ruhemann's Purple

A chemical used to visualize fingerprints.

Successive Classification

A method of classifying fingerprints based on characteristics.

Superglue

A chemical used in fuming to visualize latent fingerprints.

Tented Arch

An arch fingerprint with a pronounced upward thrust.

Ulnar Loop

A loop fingerprint that opens toward the little finger.

Whorl

A fingerprint pattern that has two or more deltas.

Porous

Absorbs

Different Techniques and Sequence from least to most destructive:

1. Visual Examination

2. Alternative Light Examination

3. Superglue fuming

4. Dye stain

Visual Examination

Any light available without an illuminating device

Alternate Light Examination

Using a device, Deliberately cause luminescence

Superglue Fuming

Sticks to the oil of latent print (permanent)

Dye Stain

Fluorescent

Biological Evidence

Evidence that is derived from biological sources, such as blood.

Angle of Impact

The angle at which a blood droplet strikes a surface.

Chromogenic Substance

A substance that produces a color change in a chemical reaction.

Area of Convergence

The point where the lines of blood spatter intersect, indicating the origin of the blood.

False Negative

A test result that incorrectly indicates no presence of a substance.

Area of Origin

The three-dimensional location from which blood spatter originated.

False Positive

A test result that incorrectly indicates the presence of a substance.

Arterial Spurt

Blood that is expelled from a severed artery, often in a spurt.

Hemastix

A test strip used to detect the presence of blood.

Back Spatter

Blood that is directed back towards the source of the force that caused the spatter.

Heme Group

The iron-containing component of hemoglobin that binds oxygen.

Castoff Patterns

Blood patterns created when blood is flung from a moving object.

Hemoglobin

The protein in red blood cells that carries oxygen.

Directionality

The direction in which blood droplets travel.

Kastle-Meyer Test

A presumptive test for the presence of blood.

Drip Patterns

Patterns formed by blood droplets falling vertically onto a surface.

Luminol

A chemical that emits light when it reacts with blood.

Erythrocytes

Red blood cells that carry oxygen throughout the body.

Oxidation

A chemical reaction that involves the loss of electrons, often producing rust or color changes.

Expirated Bloodstain Patterns

Blood patterns created when blood is expelled from the nose or mouth.

Phenolphthalein

A chemical used in a presumptive test for blood that changes color.

Exsanguination

The process of losing a significant amount of blood.

Presumptive Test

A test used to determine the likelihood that a substance is present.

Forward Spatter

Blood that travels away from the source of the force that caused the spatter.

Screening Test

A preliminary test to determine if further testing is needed.

Impact Stains

Blood stains resulting from the impact of a blood source.

Serology

The study of blood serum and its components.