Forensics Chapter 4: Fibers Flashcards

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What does 'amorphous' mean in relation to fibers?

Without a defined shape; fibers composed of a loose arrangement of polymers that are soft, elastic, and absorbing.

What does 'crystalline' mean in the context of fibers?

Geometrically shaped; fibers composed of polymers packed side by side, making them stiff and strong.

What is 'direct transfer'?

The passing of evidence, such as a fiber, from victim to suspect or vice versa.

Define 'fiber'.

The smallest indivisible unit of a textile, which must be at least 100 times longer than wide. Signup and view all the answers

What is a 'mineral fiber'?

A collection of mineral crystals formed into a recognizable pattern. Signup and view all the answers

What is a 'monomer'?

Small, repeating molecules that can link to form polymers. Signup and view all the answers

What is a 'natural fiber'?

A fiber produced naturally and harvested from animal, plant, or mineral sources. Signup and view all the answers

Define 'polymer'.

A substance composed of long chains of repeating molecules (monomers). Signup and view all the answers

What does 'secondary transfer' mean?

The transfer of evidence such as fiber from a source to a person and then to another person. Signup and view all the answers

Define 'synthetic fiber.'

A fiber made from a manufactured substance such as plastic. Signup and view all the answers

What is a 'textile'?

A flexible, flat material made by interlacing yarns. Signup and view all the answers

What is 'warp' in weaving?

A lengthwise yarn or thread in a weave. Signup and view all the answers

What is 'weft'?

A crosswise yarn or thread in a weave. Signup and view all the answers

What does the term 'yarn (thread)' refer to?

Fibers that have been spun together. Signup and view all the answers

What does fiber represent in terms of evidence?

Class evidence that is not specific to a single person. Signup and view all the answers

Why must fibers be collected within 24 hours?

An estimated 95% of all fibers may have fallen from a victim or been lost from the crime scene. Signup and view all the answers

What is the process for collecting fiber evidence?

Using tape, forceps, a vacuum, or a sticky lint roller to collect fibers, and packaging them separately. Signup and view all the answers

What does 'sampling fiber evidence and analysis testing' entail?

Identifying the type of fiber and its characteristics, often using microscopy techniques. Signup and view all the answers

What factors are evaluated in fiber evidence?

Type of fiber, fiber color, number of fibers found, where the fiber was found, and time between crime and fiber discovery. Signup and view all the answers

Differentiate between natural fibers and synthetic fibers.

Natural fibers come from animals, plants, and minerals; synthetic fibers are produced from manufactured substances. Signup and view all the answers

What are plant fibers composed of?

Polymers, or long repeating molecules, primarily cellulose. Signup and view all the answers

What are mineral fibers?

Fibers derived from mineral sources that do not have a protein or cellulose structure. Signup and view all the answers

What is a regenerated fiber?

A fiber derived from cellulose, primarily from plant sources. Signup and view all the answers

What defines synthetic polymer fibers?

Fibers that originate with petroleum products and are non-cellulose-based. Signup and view all the answers

What are the advantages of synthetic fibers?

Stronger than natural fibers and unaffected by microorganisms. Signup and view all the answers

How does weaving relate to textiles?

It involves arranging lengthwise threads (warp) side by side with crosswise threads (weft). Signup and view all the answers

Study Notes

Fiber Types and Properties

Amorphous Fibers: Lack defined shape, soft and elastic, like cotton.
Crystalline Fibers: Geometrically structured, stiff and strong, like flax.
Natural Fibers: Sourced from animals, plants, or minerals, composed of polymers.
Synthetic Fibers: Manufactured from substances like plastics; categorized as regenerated fibers and synthetic polymer fibers.

Fiber Transfer Methods

Direct Transfer: Evidence (e.g., fibers) passed directly between victim and suspect.
Secondary Transfer: Fibers transferred from a source to a suspect, then to a victim.

Fiber Collection and Evidence Protocol

Collect fibers within 24 hours to prevent loss (95% fiber loss estimate).
Use tape, forceps, or a vacuum for collection; fibers are placed on clean paper and sealed in evidence bags.
Record precise locations of fiber evidence for admissibility in court.

Fiber Analysis Techniques

Use visual identity (color, shape) to classify fibers.
Analyze fibers with non-destructive methods: polarizing light microscopy, infrared spectroscopy, microspectrophotometry, and ultraviolet light analysis.

Evaluating Fiber Evidence

Assess fiber type, color, quantity, location of find, and textile origin.
Consider multiple transfers and the type of crime to contextualize fiber significance.
Time between crime and fiber discovery affects evidence reliability.

Fiber Classification Overview

Natural Fibers: Derived from animal (protein-based), plant (cellulose), or mineral sources; include seed (cotton), leaf (manila), stem (flax), and fruit (coir) fibers.
Synthetic Fibers: Include several types such as rayon, nylon, and polyester, derived from petroleum; strong but can degrade in sunlight.

Special Fibers and Their Uses

Animal Fibers: Protein-based, include wool from sheep or silk from silkworms; used in textiles and bedding.
Plant Fibers: Composed mainly of cellulose; can be thick or fine, often brittle, with common sources including cotton and flax.
Mineral Fibers: Not composed of proteins or cellulose; includes fiberglass (insulation) and asbestos (historically used in building materials).

Yarn and Textile Production

Yarns: Formed by spinning shorter fibers; can be combined for desired strength or texture.
Textiles: Created through weaving; historical origins trace back to early human developments in the Stone Age with flax and animal fibers.

General Characteristics

Fibers must be considerably longer than wide; typically 100 times longer than their width.
Fiber evidence holds potential uniqueness, making it valuable in crime investigations.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on fibers in forensics with these flashcards from Chapter 4. Learn about different types of fibers, their properties, and the concept of direct transfer of evidence. Perfect for students preparing for exams in forensic science.