Chapter 4: A Study of Fibers + Textiles Flashcards
Characteristics of Fibers
- create a link between crime and suspect
- trace evidence
- locardś exchange principle
- direct transfer
- secondary transder > victim picked up the fibers and transferred them
- early collection is important - 24hrs
- only fibers you would not expect to find
How do forensic scientists use fibers?
- type
- color
- # of fibers
- where the fiber is found
- textile the fiber came from
- multiple fiber transfers
- type of crime committed
- time between crime & discovery of the fiber
How are fibers collected?
- vacuums
- sticky tape
- forceps
- be accurate!
Most common form of fiber transfer is shedding of a ____
textile
Steps to Taking a Fiber
- Identify the color/shape/type
- Match it to fibers from the suspects source such as a car or house
- One fiber
- More than one
Examples of Textiles
clothing, carpets & upholstery
How are they made?
weaving or intertwining yarns together
How is yarn made?
fibers that are spun together
What are the 2 types of fibers?
natural and synthetic
Where do natural fibers come from?
plants, animals, and minerals mined from the ground
Silk
- cocoons of the caterpillar
- shimmering appearance is caused by the triangular structure of the fiber. It scatters light
- clothing and bedding
- doesn´t easily shed
Minerals
- neither protein or cellulose
- ex. fiberglass > fibers are very short, weak and brittle. Used as insulation
- asbestos > durable. Used in brake linings, ceiling tiles, floor tiles
Plant
- specialized plant cells
- grouped from the part of the plant they come from
- seeds, fruits, stems & leaves all produce plant fibers
- all have diff. characteristics
- most common is cotton
- short > 2-5cm
- become brittle over time
- trace evidence
Animal Fibers
- can come from 3 sources: hair, fur and webbing
- all are made of proteins
- used in clothing, carpets, curtains & bedding
Regenerated Fibers
- made from cellulose and are mostly plant
- ex. rayon - found in carpets
Synthetic
- made w/ petroleum products and are non cellulose based
- totally man-made
- textiles and ropes
- strong
- cannot be destroyed by microorganisms
- deteriorate in bright light
- melt at low temperatures
Polyester
- most common
- fleece & wrinkle resistant pants
- can be added to natural fibers to provide strength
Nylon
- similar to polyester
- easily broken down by light & concentrated acid
Acrylic
- light and fluffy
- clothing tends to ball or pill
- inexpensive
Olefins
- high performance
- quick drying
- resistant to wear
Synthetic Fibers
(man made fibers)
- 1/2 of the fibers produced today are man made
- there are 2 types of synthetic fibers
Natural vs. Synthetic Fibers: Natural
- can be destroyed by microorganisms
- plants, animals, minerals
Natural vs. Synthetic Fibers: Synthetic
- man made or combination of natural and synthetic
- durable
Fibers that are too short to make textiles are spun together to make ____
yarn
- can be spun thick, thin, loose or tight
- weave pattern is 1 way that fibers are diff.
What is a big yarn?
rope
Fibers can be woven into _____ or _____
textiles, fabrics
There are how many weave patterns?
5
Another way fibers are diff. is the # of threads packed together in any given amount of fabric - this is the _____
thread count
Classify: Wool
natural
Classify: Rayon
semi-synthetic
Classify: Silk
natural
Classify: Linen
natural
Classify: Polyester
synthetic
Classify: Acrylic
synthetic
Classify: Cotton
natural
Classify: Mohair
natural
Classify: Nylon
synthetic
Classify: Jute
natural
