Trace Evidence Flashcards

Trace Evidence Overview

• Trace evidence refers to physical evidence present in small quantities at a crime scene, crucial for forensic analysis.

Examples of Trace Evidence

• Common types include hair, fibers, paint chips, body fluids, stains, powders, explosive residues, glass particles, vegetative matter, metal particles, and soil.

Unusual Types of Trace Evidence

• Can include non-traditional items like torn paper, itching powder, ashes, spiders, matches, grease, and linoleum.

Physical Properties

• Characteristics that do not alter a substance's identity include odor, color, boiling point, density, and refractive index.

Chemical Properties

• Determine how a substance transforms into another with distinct physical properties, important for chemical analysis in forensics.

Qualitative Analysis

• Involves identification of substances found at crime scenes using various laboratory techniques by forensic chemists.

Human Hair as Evidence

• Frequently recovered in violent crime investigations, human hair can provide significant insights into the scene.

Information from a Single Hair

• A single hair can reveal whether it comes from a human or animal, race of the individual, location on the body, if it was forcibly removed, exposure to chemicals, and potential drug ingestion.

Hair Structure

• Cuticle: The outer layer composed of overlapping scales.
• Cortex: Inner layer containing keratin, pigment granules, and air sacs known as cortical fusi.
• Medulla: Central layer that runs along the cortex.

Scale Patterns in Hair

• Three primary scale patterns:
  • Coronal: Crown-like (e.g., small rodents, bats).
  • Spinous: Petal-like (e.g., cats).
  • Imbricate: Flattened scales (e.g., most humans).

Hair Pigmentation and Characteristics

• Melanin: Pigment particles that provide color to hair.
• Cortical Fusi: Air spaces primarily located near the root but can be found along the hair shaft.

Medulla Classifications

• Types include intermittent, fragmented, continuous, stacked, and absent.

Medullary Index

• Calculated by measuring the diameter of the medulla in relation to the hair's overall diameter.

Hair Growth Phases

• Anagen: Active growth phase lasting up to five years.
• Catagen: Resting phase where hair is not growing.
• Telogen: Dying phase, preparing to fall out, lasting two to six months.

Hair Shape

• Varies based on cross-section, which can be round, oval, or crescent, influencing if hair appears straight, curly, or kinky.

Historical Context

• Napoleon died in the year 1821, marking a historical note relevant to investigations.

Advantages of Hair as Evidence

• Hair is relatively easy to collect and store, is externally available, and can yield significant forensic information.

Collection Methodology

• An accurate timeline of evidence collection requires hair samples from various parts of the body.

Control Samples

• Necessary for comparison, including samples from the victim, suspects, and anyone else who might have left hair at the scene.

Hair Root and Shaft

• Root: Contains nuclear DNA useful for individual identification.
• Shaft: Abundant in mitochondrial DNA, inherited maternally, providing familial links.

Variations in Human Hair Roots

• Appearance of human hair roots differs depending on whether hair was forcibly removed or naturally shed during the telogen phase.

This quiz provides a quick overview of trace evidence, which is crucial in crime scene investigations. It includes definitions, examples, and even unusual types of trace evidence to enhance your understanding of this forensic topic. Perfect for students and professionals in forensic science!