11. Trace Evidence Analysis Flashcards

1
Q

What is trace evidence ?

Name some examples

A

Very small quantities of materials
Locards principle - every contact leaves a trace
Key examples - hairs fibres and glass fregments

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2
Q

Whats inceptive search ?

A

Extract distinctive material

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3
Q

Whats reactive search ?

A

Looking out for particular material based on other information

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4
Q

Name some recovery methods

A
Shaking
Swabbing
Vacuuming 
Tape-lifting 
Brushing
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5
Q

What is naturally shed hair called ?

A

Telegen

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6
Q

What is torn out hair called ?

A

Anagen

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7
Q

What is hair comprised on ?

A

Keratin

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8
Q

What are the racial origins of hair ?

A

Caucasoid
Mongoloid
Negroid

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9
Q

Whats the structure of hair ?

A

Outside - cuticle
Inside - cortex

Medulla
Cortical fusi
Pigment granule

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10
Q

Whats a fibre ?

A

Smallest unit of a textile which has been spun into thread

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11
Q

Why can fibre evidence be individualised ?

A

Because of the variety of physical and chemical characteristics

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12
Q

What are natural fibres ?

A
Animal fibres ( silk, wool, hair ) vegtable fibres ( linen, cotton, jute, kapok, coir )
mineral fibres ( asbestos )
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13
Q

What are organic fibres ?

A

Synthetic polymers - polyethene,polyamide,polyester

Natural polymers -
Cellulose, materials, rubber

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14
Q

What are inorganic fibres ?

A

Carbon, ceramic, glass, metal

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15
Q

How to compare fibres ?

A

Establish points of identity

Avoud contamination

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16
Q

What can a compound microscrope see from fibres ?

A
Diamater
Shape
Surface features
Colour
Refractive index
Burefringence - determinning chemical nature
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17
Q

Stereo microscope

A

Low magnification

Hairs - classify individualise

Natural fibres - identify classify, finres appearance and distribution

Sumthetic fibres - indentify classfiy fibres appearance and distribution

18
Q

Compoun/polarised microscopy

A

High magnification
Hair - classify measure identify features

Natural fibres - classify measure indentify features fluorescence

Synthetic fibres - classify and measure fuvres by optical properties, refractive index , birefringence

19
Q

Comparison microcscapy

A

Manification ranges

Hair - comapre questioned and knows fibres

20
Q

UV visible microspectrophotometry

A

Characterises colour of the fibre

21
Q

Infared microspectroscopy

A

Identify molecular composition of the Phiber

22
Q

Thin layer chromatography

A

Separate the dyes extracted from the fibre

23
Q

What colour is 650nm ?

24
Q

What nm is violet ?

25
Technique of uv spectroscopy
Hair - identify coloursnts and dues on the hair Natural fibres - identify dyes on fibres Synthetic fibres - identify dyes on fibres
26
Technique of IR spectroscopy
Hair - na Natural fibres - na Synthetic fibres - identify , classify the chemical nature of the fibre
27
Technique of thin layer chromotography
Hair, natural fibres, synthetic fibres - identify dyes and chemical treatments
28
Technique of neutron activation analysis
Hair - identify and quantify trace elements in hair Natural fibres - na Synthetic fibres - na
29
What is glass ?
A amorphous solid based on sand , manifactured at 1600c using silican or limestone or alumina
30
How is glass classified and individualised?
``` Flatness Optical prowprties Density Refractive index Analyse of trave elements ```
31
Float glass will fluoresce under how much uv ?
254nm
32
How to determine glass density ?
Suspending fragments in liqudi of known density
33
What 2 ways to analyse for trace metals in glass ?
Optical emission | Or x-ray fluorescence soectroscopy
34
What year was the glass case in new zealand ?
1991
35
Pharmacy was robbed , the suspects clothes were analysed to find what?
11 glass fragments and small flakes of yellow paint were found on suspect A 3 fragments and more yellow paint chils found on B
36
Glass was examined and this showed ?
Flat glass urgaves and uv fluorescence showed fragmenrs were plate glass
37
What was concluded ?
Glass evidence supported paint chips
38
What are paint chils formulaed oht of ?
Binder, pigment and solvent
39
Whats the key component of paint chips?
Pigemnt
40
How are paint chips examined ?
Microscopy , colour looked at via Microspectrophotometry Chemical charcetristics - ir spectroscopy Organic compoents - purolysis gad chromotography