Forensics Chapter 3 and 4 Flashcards

Questions and Answers

How and when is hair considered class evidence, and when is it considered individual evidence?

Hair is considered class evidence when the follicle is not attached, and individual evidence when the follicle is attached.

What are some functions of hair for mammals?

Regulate body temperature, protect against sunlight, decrease friction, act as a sensory organ.

What are the characteristics of hair structure?

Follicle: club-shaped structure embedded in the skin; Hair shaft: produced by follicle; Inner medulla: runs down center of the hair; Cortex: pigmented layer inside cuticle; Cuticle: outer covering of hair shaft, resembles 'roof shingles'.

List 6 different regions of body hair.

Head, eyebrows and lashes, mustache and beard, underarms, overall body (auxiliary), pubic. Signup and view all the answers

How do chemical treatments of hair affect it?

Bleaching disturbs scales on cuticle and removes pigment, leaving hair brittle and yellowish; Dyeing colors cuticle and cortex. Signup and view all the answers

What are the characteristics of animal hair?

Pigmentation is denser towards the medulla; Can abruptly change colors; Medulla index is thicker than humans; Cuticle scales resemble petals (spinous) or a stack of crowns (coronal). Signup and view all the answers

What are the characteristics of human hair?

Pigmentation is denser towards the cuticle; Cannot change colors at random; Medulla index is thinner than animals; Cuticle scales are flat and narrow (imbricate). Signup and view all the answers

What does the animal hair cuticle resemble?

Resembles petals (spinous) or a stack of crowns (coronal). Signup and view all the answers

What does the human hair cuticle look like?

Flat and narrow (imbricate). Signup and view all the answers

What are the types of medulla patterns?

Continuous, interrupted, fragmented/segmented, solid, or none. Signup and view all the answers

What information can macroscopic investigation provide?

Indicates length, color, and curliness. Signup and view all the answers

What does microscopic investigation indicate?

Indicates fine detail in hair. Signup and view all the answers

What does contrast microscopy show?

Shows presence of dye or other treatments. Signup and view all the answers

What details can electron microscopes provide?

Details of surface and interior of sample. Signup and view all the answers

What substances can be detected by testing the hair shaft?

Chemicals absorbed by skin can be detected; various substances tested. Signup and view all the answers

What does neutron activation analysis determine?

Determines concentrations of substance in sample. Signup and view all the answers

Why is testing the hair follicle done first?

It is cost effective and fast. Signup and view all the answers

What is direct transfer of fibers?

Fibers transferred from victim to suspect (or vice versa). Signup and view all the answers

What is secondary transfer of fibers?

Fibers are picked up by suspects elsewhere, then transferred to the victim. Signup and view all the answers

How are fibers classified?

Small fibers easily shed from most textiles and can become trace evidence. Signup and view all the answers

What does infrared microscopy reveal?

Reveals some chemical structures of other fibers that can look very similar. Signup and view all the answers

What is the purpose of a burn test?

Burn the fibers to see the residue, reaction, and smell. Signup and view all the answers

What does a dissolve test involve?

Dissolve the fiber in various liquids and chemicals. Signup and view all the answers

List 3 natural fibers.

Animal (silk), plant (fruit fibers), mineral (asbestos). Signup and view all the answers

List 2 synthetic fibers.

Regenerated (nylon), polymer (polyester). Signup and view all the answers

Study Notes

Hair as Evidence

Hair without a follicle is class evidence; the follicle contains DNA and is necessary for individual identification.
Hair with an attached follicle is considered individual evidence, allowing for more specific identification.

Functions of Hair in Mammals

Regulates body temperature and provides insulation.
Offers protection against sunlight damage.
Reduces friction during movement.
Serves a sensory function, detecting environmental stimuli.

Structure of Hair

Follicle: Club-shaped structure embedded in the skin, crucial for hair growth.
Hair Shaft: Result of follicle activity, extending outside the skin.
Inner Medulla: Core structure running along the hair.
Cortex: Pigmented layer providing color and strength inside the cuticle.
Cuticle: Outer covering that resembles roof shingles, protecting the inner layers.

Regions of Body Hair

Head
Eyebrows and eyelashes
Mustache and beard
Underarms
Auxiliary (overall body)
Pubic area

Effects of Chemical Treatments on Hair

Bleaching: Disrupts cuticle scales and removes pigment, resulting in brittle, yellowish hair.
Dyeing: Alters the color of the cuticle and cortex of the hair shaft.

Characteristics of Animal Hair

Denser pigmentation towards the medulla.
Can exhibit abrupt color changes in patterned bands.
Thicker medulla index than human hair.
Cuticle scales are either spinous (petal-like) or coronal (crown-like).

Characteristics of Human Hair

Denser pigmentation towards the cuticle.
Lacks random color changes.
Thinner medulla index compared to animal hair.
Cuticle scales are imbricate (flat and narrow).

Medulla Patterns

Medulla can be continuous, interrupted, fragmented/segmented, solid, or absent.

Investigation Techniques

Macroscopic Investigation: Assesses general characteristics like length, color, and curliness.
Microscopic Investigation: Examines fine details, aiding in identification.
Contrast Microscopy: Identifies presence of dyes or treatments on hair.
Electron Microscopy: Provides detailed views of hair surfaces and structures.

Hair Analysis for Substances

Chemicals absorbed by skin can be detected in hair analysis.
Hair shafts can reveal a timeline of exposure to toxins through section examination.

Neutron Activation Analysis

Analyzes concentrations of substances within a hair sample, enhancing forensic analysis.

Testing Hair Follicles

Initial microscopic assessment of the follicle is cost-effective and efficient.
May indicate blood type if no match is found; DNA analysis offers high confidence identification.

Fiber Transfer Types

Direct Transfer: Fibers move directly between victim and suspect.
Secondary Transfer: Suspects pick up fibers from other locations, transferring them to the victim.

Fiber Characteristics

Fibers are trace evidence that can easily shed from textiles and help link suspects to crime scenes.

Fiber Investigation Techniques

Infrared Microscopy: Reveals chemical structures of similar-looking fibers.
Polarizing Light Microscope: Utilizes specific light wavelengths to examine fiber properties.
Burn Test: Analyzes fibers' reaction to fire for residue and smell.
Dissolve Test: Identifies fibers by dissolving them in different chemicals.

Types of Natural and Synthetic Fibers

Natural Fibers: Include animal (e.g., silk), plant (e.g., fruit fibers), and mineral (e.g., asbestos).
Synthetic Fibers: Include regenerated fibers like nylon and polymer fibers like polyester.

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Description

Test your knowledge on the key concepts from Forensics chapters 3 and 4. This quiz covers the classification of hair as evidence and its functions in mammals. Enhance your understanding of forensic science with these flashcards.