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1st Year sem 1: Forensic Science Principles > L7: HAIR, FIBRES, GLASS AND PAINT EVIDENCE > Flashcards

L7: HAIR, FIBRES, GLASS AND PAINT EVIDENCE Flashcards

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1
Q

hair is mainly comprised of?

A

keratin

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2
Q

how much does hair grow per month?

A

1cm

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3
Q

Hair fibres grow in what pattern?

A

cyclic growth pattern

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4
Q

whats 1000 days of growth and whats 100 days fo rest?

A

1000 - anagen

100 - telegen

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5
Q

whats the intermediate period in hair called?

A

catagen

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6
Q

what percent is anagen?

A

80-90% anagen

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7
Q

what percent tis telegen?

A

10-18% telegen

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8
Q

what are naturally shed hairs ?

A

mainly telegen undamaged hair root

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9
Q

anagen has a _____ root.

A

damaged

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10
Q

outer shaft of hair is ___

A

cuticle

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11
Q

main body of hair ____

A

cortex

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12
Q

core of the fibre is ____

A

medulla

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13
Q

hair diameter is between?

A

approximately 40 - 100 mm

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14
Q

what are the key characteristics of hair?

A

Length, shape, size,

colour, stiffness, curliness

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15
Q

European hair is known as?

A

caucasoid

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16
Q

features of caucasoid hair are?

A
  • Fine to medium coarseness
  • Straight or wavy
  • Oval to circular hair shaft
  • Even pigmentation (medium – fine)
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17
Q

Asian hair is known as

A

Mongoloid

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18
Q

features of Mongoloid hair?

A
  • Coarse and straight with large diameter
  • Circular cross-section
  • Large pigment granules; reddish
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19
Q

African hair is known as?

A

negroid

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20
Q

features of negroid hair?

A

Kinks and curls, flattened cross- section
Largest pigmentation granules
Opaque fibre

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21
Q

do hairs have a lot of individualising features?

A

no

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22
Q

do FBI to hair analyses?

A

no

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23
Q

what difficult with hair analysis ?

A
  • Variation between hairs from the same source
  • Quality (length of hair)
  • Time difference
  • Experience of forensic examiner
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24
Q

There are ___ natural and synthetic fibres

A

countless

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25
Q

fibres secondary transfer is ____

A

fast

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26
Q

where are fibres strong?

A

along the length

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27
Q

fibres have low?

A

solubility and elasticity

28
Q

do fibres have a high or low melting point?

A

high melting point

29
Q

How long are animal fibres?

A

10 – 80 microns

30
Q

what are natural fibres?

A

Animal fibres
Veg fibres
Mineral fibres

31
Q

what are natural animal fibres?

A

silk
wool
hair

32
Q

what are natural veg fibres?

A 
linen
cotton
jute
kapok
coir
33
Q

what are mineral fibres?

A

asbestos

34
Q

what are synthetic fibres?

A

organic fibres and inorganic fibres

35
Q

name organic fibres that are synthetic polymers?

A

polyethene, polyvinyl derivatives, polyurethane, polyamide, polyester

36
Q

name organic fibres the are natural polymers?

A

cellulose, materials, rayon, viscose, modal, rubber

37
Q

Name inorganic fibres

A

carbon, ceramic, glass, metal,

38
Q

what do cotton fibres look like?

A

irregular “U-shaped” appearance in cross-section

a twisted undulating and irregular appearance along their length

39
Q

what does wool look like?

A

More cylindrical appearance with circular/ oval cross-section
Scalar features along the length of the fibre (hair-like)

40
Q

what do synthetic fibres viscose or triacetate look like?

A

Appearance of both examples due to manufacture process

Indentations along the length give the fabric an appropriate quality appearance.

41
Q

whats a good thing about fibre evidence?

A

strongly classifiable and often individualisation may be possible.

42
Q

How to find out what type of polymer a fibre is?

A 
Refractive index and birefringence
or 
infrared microscope 
or
raman micro-spectrometry
43
Q

How to find out the colour of a fibre?

A

UV-Visible microspectrophotometry

44
Q

How to find out a dye mix ?

A

Chromatography

45
Q

which technique for fibre analysis is destructive?

A

chromatography

46
Q

what is glass comprised of?

A

Silica with sodium carbonate

47
Q

what additives improve the durability of glass?

A

limestone

alumino-silicate

48
Q

natural glass has what colour tint and why?

A

green because of Fe2O3 from sand

49
Q

Glass is very ___ and can be _____

A

classifiable

individualised

50
Q

what forensic analyses for glass can be done?

A

• Physical matching of fragments
• Flatness/ curvature, optical properties
and fracture surfaces
• Density of glass
• Refractive index (RI) of fragments
• Elemental analysis of trace elements (metals)

51
Q

how is paint usually evidence?

A

chips or scrapings

52
Q

what is paint made from?

A

binder
pigment
solvent

53
Q

what does binder do in paint?

A

helps paint adhere is surface

54
Q

what does pigment do in paint?

A

provides colour and opacity

55
Q

what does solvent do in paint?

A

gives liquid properties, dries during use

56
Q

how thick is paint layer usually?

A

20mm – 50mm upwards

57
Q

white and black paint are usually ______

A

inorganic

58
Q

pigments are generally ?

A

insoluble

59
Q

binders are based on?

A

oils, gums or resins

60
Q

forensic analysis of paint involves

A

Physical matching of fragments

61
Q

How else can paint be analysed?

A

Microscopic examination and measurement of layer thickness and
appearance

62
Q

How to find the chemical composition of paint ?

A

FTIR or Raman spectroscopy

63
Q

How to find the colour of paint?

A

UV-Vis spectroscopy

64
Q

How to find elemental composition of paint?

A

X-ray analysis

65
Q

How can crystalline pigments be analysed?

A

X-ray powder diffraction

1st Year sem 1: Forensic Science Principles (14 decks)

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