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Forensic Science - Sheppard > Unit 6 - Fibers > Flashcards

Unit 6 - Fibers Flashcards

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Biology 101 flashcards
1
Q

Can fiber evidence have probative value?

A

Yes

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2
Q

Characteristics of synthetic fibers

A

Uniform and regular shape of cross section
Stronger
More chemically inert

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3
Q

Can a piece of fabric be individualized to a particular garment?

A

Yes, but only if the piece fits a tear or rip in the garment.

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4
Q

Can a fiber be individualized to a particular garment?

A

No. Fibers are class evidence.

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5
Q

Difference between a fabric and a fiber

A

Fabric - made from fibers

Fibers - made of twisted elements that are either natural or artificial.

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6
Q

Is silk synthetic or natural?

A

Natural

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7
Q

Most common type of natural fiber

A

Cotton

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8
Q

Most common type of synthetic fiber

A

Nylon

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9
Q

Can an investigator use the way a fabric accepts a specific dye to identify and compare samples?

A

Yes

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10
Q

Optical microscopy

A

The most important method of fiber identification

Involves polarizing light and comparison microscopes

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11
Q

Electropherogram

A

Plot of results from an analysis done by electrophoresis

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12
Q

Natural fibers

A 
Cotton
Wool
Linen
Silk
Cashmere
Jute
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13
Q

Synthetic Fibers

A 
Nylon
Polyester
Acrylic
Plastic
Rayon
Acetate
Dacron
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14
Q

Polymer

A

A molecule consisting of many repeating units. Can be naturally occurring or synthetic.

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15
Q

Are all fibers polymers?

A

Yes

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16
Q

What types of tests can be used to test the dye in a particular fiber?

A

Chemical tests or chromotography

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17
Q

Is linen natural or synthetic?

A

natural

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18
Q

For there to be an association between a questioned fiber and an unknown fiber, what percentage of tests you run on the two samples must have identical results?

A

100% One off means the two fibers cannot be associated.

19
Q

What was the first truly synthetic fiber to be discovered and sold?

A

Nylon

20
Q

What fiber will fluoresce under ultraviolet light?

A

Cotton

21
Q

The Amanda Davies case showed the importance of what?

A

fiber transfer

22
Q

First person convicted on the basis of fiber evidence

A

Wayne Williams

23
Q

Tests that can be done in lab to analyze fibers (in addition to what we did in class)

A

refractive index,
any type of chromotography,
optical microscopy
any infrared study

24
Q

Properties that should be examined when comparing two fibers

A 
birefringence
diameter
color
cross-section
fluorescence
25
Q

Fibers that come from plant sources

A

Linen

Cotton

26
Q

Fibers that come from animal sources

A

Asbestos

Mineral wool

27
Q

Difference between a synthetic fiber and a natural fiber

A

synthetic fibers - man made through chemical alteration of natural fibers
natural fibers - produced by plants or animals

28
Q

What does wool smell like when it is burned?

A

burning hair

29
Q

Becke line

A

a light colored halo that appears around an object when it is immersed in a liquid of a different refractive index

30
Q

Blend

A

a fabric composed of two or more different types of fiber, usually as warp and weft

31
Q

Chromatography

A

a method of separating components of mixtures based on preferential absorption or partitioning of components in a gas, liquid, or solution

32
Q

Chromatogram

A

the record of chromatographic separation

33
Q

Density

A

a physical property of matter

D = M/V

34
Q

Elute

A

in chromatography, to extract one material from another, usually by means of a solvent

35
Q

Filament

A

single strands of material, usually twisted or bonded together to form a thread or yarn

36
Q

Fluorescence

A

the absorption of light at one wavelength and its remission at a longer wavelength

37
Q

Plain

A

simplest and most common weave. The warp and weft yarns pass under each other alternating

38
Q

Twill

A

the warp yarn is passed over one to three weft yarns before going under one.
Makes a diagonal weave pattern

39
Q

Satin

A

yarn lacing is not uniform. Creates long floats

Interlacing weaves pass over four or more yarns.

40
Q

Viscosity

A

the resistance of fluid to flow

41
Q

Warp

A

the lengthwise yard or thread in a weave

42
Q

Weft

A

the crosswise yarn or thread in a weave; also called the woof.

43
Q

Yarn

A

a continuous strand of fibers or filaments, either twisted or not

Forensic Science - Sheppard (5 decks)

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