Trace Evidence

These flashcards cover key concepts related to trace evidence in forensic science, including definitions, types, collection methods, and analysis techniques.

Trace Evidence

Small/minute material left behind from a transfer that can link a suspect to a crime scene.

Locard’s Exchange Principle

States that whenever two objects come into contact, a transfer of material will take place.

Transfer of Material

The process in which materials are exchanged between two objects in contact.

Contributing Factors to Evidence Loss

Factors that may cause trace evidence to be undetected, lost, or destroyed.

Environment (Trace Evidence)

External conditions like rain or wind that can impact the visibility and recoverability of trace evidence.

Activity (Trace Evidence)

Actions such as washing or burning that can destroy potential trace evidence.

Substrate (Trace Evidence)

The surface where trace evidence is found, which can affect the collection process.

Types of Trace Evidence

Includes hair, gunshot residue (GSR), fibers, paint, and more.

Visual Examination

The initial step to detect and identify trace evidence at a crime scene.

Collection of Trace Evidence

The careful process of gathering trace materials to prevent loss or contamination.

Picking Method

A collection method using forceps to pick visible trace materials.

Tapelifting Method

A collection technique using clear fingerprint tape to recover surface material.

Scraping Method

A collection method using a spatula to recover materials embedded in fabric.

Vacuuming Method

Using a specialized vacuum to collect evidence from surfaces.

Combing Method

A technique to collect trace evidence from an individual’s hair.

Clipping Method

Collecting trace evidence from fingernails using a clipping approach.

Stubbing for pGSR

Collecting primer gunshot residue (pGSR) using carbon-coated stubs.

Hair Evidence

Human hair is a slender outgrowth of the epidermis composed primarily of keratin.

Human Hair Growth Rate

Average human hair grows at a rate of approximately 1 cm per month.

Hair Morphology

The physical structure of hair which can vary in length, color, and thickness.

Human Hair Follicle

The root of the hair embedded in the follicle from which the hair grows.

Cuticle (Hair Structure)

The outer layer of the hair shaft composed of overlapping scales.

Cortex (Hair Structure)

The main body of the hair shaft containing pigment granules and other features.

Medulla (Hair Structure)

The cellular column running through the center of the hair.

Anagen Phase

The active growth phase of hair where it grows and is often pigmented.

Telogen Phase

The dormant phase of hair growth where hairs are loosely anchored and easily shed.

Microscopic Examination

Analyzing hair under a microscope to assess its characteristics.

Fiber Evidence

Fibers are elongated filaments that can come from various sources such as clothing.

Natural Fibers

Fibers derived from animal or plant sources, such as wool and cotton.

Synthetic Fibers

Man-made fibers produced from chemicals, such as polyester and nylon.

Plausible Source

The origin from which a fiber is likely to have come, used in forensic comparisons.

Paint Evidence

A colored coating used on various surfaces, analyzed for forensic identification.

Automotive Paint

Paint used on vehicles, identified by particular multilayer coatings.

Architectural Paint

Paint used for buildings that tends to be thicker and less uniform than automotive paint.

Fiber Analysis Characteristics

Factors like size, shape, and color assessed during fiber analysis.

Comparison Microscope

An instrument used to compare questioned evidence with known standards side by side.

Impression Evidence

Marks left by an object impressed onto a surface, such as shoe prints or tire tracks.

Class Characteristics

Physical features that are common among many items, such as tread patterns.

Randomly Acquired Characteristics

Unique marks or features found on an item that can link it to an individual.

Physical Fit

Determining if torn or broken materials fit together as if they were once a whole.

Pressure Sensitive Tape Analysis

Examination of tape evidence where backings and adhesives are compared.

Gunshot Residue (GSR)

Particles left on hands or surfaces after firing a weapon, analyzed for forensic evidence.

Ignitable Liquid Residue (ILR)

Residues extracted from evidence post-fire, analyzed to identify ignitable liquids.

Gas Chromatography

A method used to detect and characterize flammable residues in liquid analysis.

Paint Data Query (PDQ)

A database of automotive paint samples used for forensic identification.

Gel Lifting

A method for lifting impressions using a gelatin film that can collect wet and dry impressions.

Luminol

A chemical used to visualize latent blood impressions during crime scene investigation.

Amido Black

A chemical utilized to enhance the visibility of latent impressions on surfaces.

Electrostatic Lifting

A technique using an electric charge to collect dust particles from impressions.

Test Impressions

Creating impressions using known samples for comparative analysis with questioned evidence.

Analysis of Unknown Substances

Identification of various materials that are not immediately recognized.

Glass Analysis

Analyzing glass fragments for color, thickness, and elemental composition.

Comparison of Paint Chips

Using microscopy to compare characteristics of questioned paint chips to known standards.

Fiber Comparison Techniques

Involves comparing fibers from evidence to known standards using various analytical methods.

Trace Evidence Collection Techniques

Methods such as tapelifting or vacuuming used to safely gather trace evidence.

Hair Analysis Methods

Techniques used to differentiate between human and animal hairs in forensic analysis.

Shoe Impression Evidence

The analysis and collection of shoe impressions left at crime scenes.

Tire Impressions

Evidence formed by the pattern and characteristics of tires on surfaces.