lecture 4 - hair and fibres Flashcards
1
Q
what does hair as physical evidence require
A
- properly collected and submitted sample
- adequate number of standard/reference samples
2
Q
morphology of hair
A
- hair is appendage of skin that grows out of organ known as hair follicle
- length of hair extends from root/bulb embedded in the follicle, continues to shaft, terminates at tip end
3
Q
shaft of hair composed of
A
- cuticle
- cortex
- medulla `
4
Q
cuticle
A
- scale structure covering the exterior of hair
- scale always points towards the tip of hair
- scale pattern useful in species identification
5
Q
cortex
A
- main body of the hair shaft
- embedded with the pigment granules that impart hair with colour
- colour, shape and distribution of granules
6
Q
medulla
A
- cellular column running through centre of hair
- may be continuous, interrupted, fragmented or absent
- presence of medulla varies
- medullae also have different shapes
7
Q
root
A
- root provide tools necessary to produce hair and continue its growth
- 3 phases of growth - anagen, catagen and telogen
- when pulled from head, some translucent tissue surrounding hair shaft near root may be found
8
Q
distinguishing animal from human hair
A
- scale structure, medullary index, medullary shape
9
Q
comparing human hair, we want to match
A
- colour
- length
- diameter
- presence/absence of medulla
- pigment granules
10
Q
types of fibres
A
- wool
- mohair
- cashmere
- fur
- cotton
11
Q
man made fibres are manufactured
A
- manufactured from natural raw materials and include rayon, acetate and triacetate
- synthetics produced from synthetic chemicals include nylons, acrylic and polyester
12
Q
fibre evidence quality depends on
A
- ability to identify the origin of fibre
- be able to narrow possibilities to a limited number of sources
13
Q
strongest evidence that two different fabrics were of common origin
A
- two torn edges that can be fit together
14
Q
microscopic comparisons performed initially
A
- between questioned and standard/reference fibres
- evaluated for colour and diameter
- using comparison microscope
15
Q
morphological features that could be important in comparing fibres are
A
- cross-sectional shape of fibre
- lengthwise striations on the surface of fibre
- presence of delustering particles that reduce shine
16
Q
method for fibre comparison
A
- accomplished using infrared spectrophotometry
- molecules compose a manufacture fiber selectivity absorb the light to form characteristic pattern
- infrared light -> fibre sample -> information
17
Q
what does a micro spectrophotometer allow
A
- allows forensic analyst to view object under microscope while simultaneously obtaining its visible of infrared absorption pattern
