11. Trace Evidence Analysis Flashcards
What is trace evidence ?
Name some examples
Very small quantities of materials
Locards principle - every contact leaves a trace
Key examples - hairs fibres and glass fregments
Whats inceptive search ?
Extract distinctive material
Whats reactive search ?
Looking out for particular material based on other information
Name some recovery methods
Shaking Swabbing Vacuuming Tape-lifting Brushing
What is naturally shed hair called ?
Telegen
What is torn out hair called ?
Anagen
What is hair comprised on ?
Keratin
What are the racial origins of hair ?
Caucasoid
Mongoloid
Negroid
Whats the structure of hair ?
Outside - cuticle
Inside - cortex
Medulla
Cortical fusi
Pigment granule
Whats a fibre ?
Smallest unit of a textile which has been spun into thread
Why can fibre evidence be individualised ?
Because of the variety of physical and chemical characteristics
What are natural fibres ?
Animal fibres ( silk, wool, hair ) vegtable fibres ( linen, cotton, jute, kapok, coir ) mineral fibres ( asbestos )
What are organic fibres ?
Synthetic polymers - polyethene,polyamide,polyester
Natural polymers -
Cellulose, materials, rubber
What are inorganic fibres ?
Carbon, ceramic, glass, metal
How to compare fibres ?
Establish points of identity
Avoud contamination
What can a compound microscrope see from fibres ?
Diamater Shape Surface features Colour Refractive index Burefringence - determinning chemical nature
Stereo microscope
Low magnification
Hairs - classify individualise
Natural fibres - identify classify, finres appearance and distribution
Sumthetic fibres - indentify classfiy fibres appearance and distribution
Compoun/polarised microscopy
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
Comparison microcscapy
Manification ranges
Hair - comapre questioned and knows fibres
UV visible microspectrophotometry
Characterises colour of the fibre
Infared microspectroscopy
Identify molecular composition of the Phiber
Thin layer chromatography
Separate the dyes extracted from the fibre
What colour is 650nm ?
Red
What nm is violet ?
400