Trace Evidence Flashcards

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Questions and Answers

What is Trace Evidence?

Large amounts of physical evidence

Evidence only from closed environments

Only evidence that can be seen by the naked eye

Physical evidence found in small amounts at a crime scene (correct)

Give examples of trace evidence.

Hair, fiber, paint chips, body fluids, stains, powders, explosive residue, glass particles, vegetative matter, metal particles, and soil.

What are unusual types of trace evidence?

Torn piece of paper, itching powder, ashes, spider, match, grease, linoleum.

Define physical property.

A characteristic that does not involve a change in the identity of a substance, such as odor, color, boiling point, density, refractive index. Signup and view all the answers

What is a chemical property?

A characteristic that determines how a substance will change into another substance with different physical properties. Signup and view all the answers

What is qualitative analysis?

When investigators find substances at the scene of a crime and send them to the laboratory for identification. Signup and view all the answers

What is human hair in the context of trace evidence?

One of the most frequently found pieces of evidence at the scene of a violent crime. Signup and view all the answers

What can a single hair determine?

Human or animal, race, location in the source's body, forcibly removed, treated with chemicals, and if drugs have been ingested. Signup and view all the answers

What is a cuticle?

The outside covering of hair, made of overlapping scales. Signup and view all the answers

Define cortex in the context of hair.

The inner layer of hair made of keratin and imbedded with pigment; also contains air sacs called cortical fusi. Signup and view all the answers

What is the medulla in hair structure?

The inside layer running down the center of the cortex. Signup and view all the answers

What are the three basic scale patterns of hair?

Coronal, Spinous, and Imbricate. Signup and view all the answers

Describe coronal scale pattern.

Crown-like scales, for example in small rodents and bats. Signup and view all the answers

Describe spinous scale pattern.

Petal-like scales, found in animals like cats. Signup and view all the answers

Describe imbricate scale pattern.

Flattened scales, most commonly found in humans. Signup and view all the answers

What is melanin?

Pigment granules that give hair its color. Signup and view all the answers

What are cortical fusi?

Air spaces usually found near the root but may be found throughout the hair shaft. Signup and view all the answers

List types of medulla.

Intermittent, fragmented, continuous, stacked, and absent. Signup and view all the answers

What is the medullary index?

Determined by measuring the diameter of the medulla and dividing it by the diameter of the hair. Signup and view all the answers

What is the anagen phase of hair?

Hair that is actively growing; lasting up to 5 years. Signup and view all the answers

What is the catagen phase of hair?

Hair is not growing; it is in a resting phase. Signup and view all the answers

Describe the telogen phase of hair.

Hair that is dying and ready to fall out; lasting two to six months. Signup and view all the answers

How can hair shape vary?

It can be straight, curly, or kinky depending on the cross-section, which may be round, oval, or crescent-shaped. Signup and view all the answers

What historical event happened in 1821?

Napoleon died. Signup and view all the answers

What are the advantages of hair as evidence?

Easy to collect and store, externally available, and can provide some good information. Signup and view all the answers

What does an accurate timeline of hair collection involve?

Collections of hair must be taken from different parts of the body. Signup and view all the answers

What are control samples?

Samples from the victim, possible suspects, and others who may have deposited hair from the scene. Signup and view all the answers

What is the root of hair associated with?

Contains nuclear DNA. Signup and view all the answers

What does the hair shaft contain?

Contains abundant mitochondrial DNA, inherited only from the mother. Signup and view all the answers

How do human roots differ based on removal?

Look different based on whether they have been forcibly removed or if they are telogen hairs and have fallen out. Signup and view all the answers

Study Notes

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.

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Description

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!