LECTURE 15: HAIR AND FIBRE/ CHAPTERS ON HAIR EXAMINATION AND FIBRE Flashcards
Hair only comes from
mammals
hair is usually what kind of characteristic
generally class, however can be indivvidualised by DNA analysis and using other characterustics of colour/ split ends
human
use mainly scalp and pubic hair for analysis
Animals
guard hair, underhair
Main group
characteristics
• used overall diameter of shaft larger diameter = coarser hair
• medullary index - diam. medulla/diam. hair
• shaft shape of medulla and any inclusions
• root shape
• general hair shape
• scale pattern on cuticle
human vs animal
Human
- Consistent color and pigmentation
- Pigmentation even
- Medulla amorphus
- Medullary index ~0.3
- Root club shaped
Animal
- Often have bands of colour
- Pigmentation central
- Medulla continuous
- Medullar >0.3
- Root shape highly variable
3 types of animal hair
- 3 main types/ classes • guard – top coat • fur/wool – undercoat • tactile – whiskers - mane/ tail hair (e.g. horse) could be considered modified guard hair
1) Guard hairs = large, stiff hairs, make up the outer part of the animal’s coat. These hairs should be used for microscopic identification.
Have a widening in the upper half of the shaft, called a shield.
Below the shield, a sub-shield stricture, a narrowing of the hair to slightly less than the normal, non-
shield shaft diameter, may be accompanied by a bend in the shaft at the stricture.
2) Fur hairs = thinner, softer, providing warmth & bulk, usefulness for microscopic examination/identification
3) Vibrissa = whiskers, short to long, stiff, often white hairs around the snout & muzzle. Have a long life cycle, lost less often than the myriad guard & fur hairs of a typical animal.
Fabrics
- May consist of many different types of fibre
- Look at the weave of the material
- Analyse the pattern in which the fibres are put together
• e.g. ropes/cables can potentially tell you who the manufacturer is - If have a piece of fabric could match torn edges to clothing, rug, etc.
- Not just about murder/break-ins
- Can you tell the difference between antique and reproduction rugs
why are hairs good evidence
because they are sturdy & can survive years, carry a lot of biological information, easy & cost effective to examine.
- Hair is one of the most durable materials produced in natures – hairs from mummies which have been dead for thousands of years have been found.
hair grows from
the skin (epidermis) of the body
Follicle
= structure within which hairs grow, a roughly cylindrical tube with a larger pit
at the bottom.
hair is made of what
keratin
keratin
a tough protein-based material from which hair, nails, & horns are made in animals.
Keratinization
hardening process of hair growth
- also explains why hair doesnt hurt when cut, dead from when it peaks out of skin
follicle also contains others structures
such as blood vessels, nerves, & sebaceous glands, the latter producing oils that coat hairs, helping to keep them soft & pliable.
Hair muscles
pili arrector muscles - raise when cold - piloerection
3 phases of hair growth
1) Anagen phase
2) Catagen phase
3) Telogen phase
1) Anagen phase of hair growth
1) Anagen phase (actively growing) = follicle produces new cells & pushes them up the hair shaft as they become incorporated into the structure of the hair. Hair is moved up the shaft by a mechanical method.
Specialised cells in the follicle produce small colored granules, called melanin/pigment – give hairs color, these cells are called melanocytes.
2 types of melanin found in hairs: dark brown pigment (eumelanin) & lighter pigment (pheomelanin). The combination produce a range of hair colours.
2) catagen phase of hair growth
2) Catagen phase (resting phase) = follicle begins to shut down production of cells, the cells begin to shrink, & the root condenses into a bulb-shaped structure called a root bulb/club root.
3) Telogen phase of hair growth
3) Telogen phase (resting phase for follicle) = cell production has ceased completely, root has condensed into a bulb, held in place by a mechanical connection. When this mechanical connection breaks, follicle is triggered into the anagen phase again & the cycle renews.
healthy human head of hair
80-90% of hairs in the anagen phase, 2% in catagen phase, 10-18% telogen phase
at what phase(s) may an forensic hair examiner be able to tell if hair was forcibly removed
anagen or catagen phase
microanatomy of hair
- Root: portion that formerly was in the follicle, the proximal (direction toward the body) most portion of hair
- Shaft: main portion of the hair
- Tip: distal (the direction away from the body) most portion of the hair.
3 main structural elements in hair
1) Cuticle = is a series of overlapping layers of scales that form a protective covering. Animal hairs have scale patterns that vary by species, & these patterns are a useful diagnostic tool for identifying animal hairs.
- Humans have a scale pattern called imbricate, it is fairly common among animals.
2) Cortex = makes up the bulk of the hair. Consists of spindle-shaped cells (fusiform) that contain or constrain numerous other structures.
- Pigment granules are found in the cortex & are dispersed variably throughout the cortex, vary in size, shape, aggregation, & distribution
- Small bubbles, called cortical fusi, may appear in the cortex, vary in size & shape.
- Telogen root hairs will have an aggregate of cortical fusi near the root bulb.
3) Medulla
- Odd structures that look like very large pigment granules, called ovoid bodies, may appear irregularly in the cortex.
hair examination of non human vs human techniques
- Best ways to visualize scale patterns are with a scanning electron microscope or by making a scale cast & viewing it with a light microscope
what kind of hairs can be found and which ones are used for examination
- Areas include head, pubic, facial, chest, axillary (armpits), eyelash/eyebrow, & limbs. Typically, only head & pubic hairs are suitable for microscopic comparison.
- Hairs that do not fit into these categories may be called transitional body hairs -> stomach, chest, pubic region.
Buckling
an abrupt change in direction of the hair shaft with or without a slight twist
Shouldering
an asymmetrical cross section of hairs
can hair examination be used for ancestral estimation
yes with 85% accuracy, provided best by head and pubic hair
3 main ancestral groups are used:
Europeans (Caucasoids, includes Hispanics & Middle East), Africans (Negroids), & Asians (Mongoloids).
Pili annulati
hairs with coloured rings, the hair has alternating light & dark bands along its length, like tiger or zebra stripes. People with dark hair may have pili annulati but not know it because their hair color masks the condition.
Monilethrix
makes hairs look like a string of beads. Along the length of the hair are nodes & constrictions making the hair vary in diameter. This hair beading weakens the hair, & people suffering from monilethrix have patchy hair loss.
Pili torti
a twisting of the hair along its length, creating a spiral morphology. Cuticle is present but the twisting creates stress that leads to fractures in the cuticle & cortex.
vermin e.g.
lice
fibre classes
1) natural: any fibre that exists as a fibre in its natural state
2) manufactured: and fibre derived by a process of manufacture
fibre designation based on chemical make-up
1) Protein fibres are composed of polymers of amino acids
2) cellulosic fibres are made of polymers from carbohydrates
3) mineral fibres may be composed of silica obtained from rocks or sand
4) synthetic fibres are made of polymers that originate from small organic molecules that combine with water and air
filaments
are a type of fibre having indefinite or extreme length such as silk or manufactured fibre
yarn
- is a term for continuous strands of textile fibres, filaments or material in a form for suitable waving, knitting or otherwise in tangling to form a textile fibre
- S twist or Z twist or no twisted all
- Thread is used to join pieces of fabric together whereas yarn is a product used to make fabric
3 major types of favric
1) Woven - those fabrics composed of two sets of yarn called warp and weft and are formed by interlacing of these sets of yarn, warp runs lengthwise and weft runs crosswise
2) Knitted - I constructed of interlocking series of loops of one or more yarns and fall into two major groups, warp knitting and weft knitting, warp is length wise and weft is crosswise, courses and wales
3) Nonwoven - assembly of textile fibres held together by mechanical interlocking in a random web format by fusing of the fibres or by bonding with a cementing medium
fibre characteristic
- Crimp is the waviness of a fibre expressed as crimps per unit length
- colour is introduced to manufactured fibres with dyes or pigments well naturally fibres maybe originally white or off white or a shade of brown
- cross sectional shape is the shape of an individual filament when cut at a right angle to its long axis is a critical characteristic of fibre analysisa fibres length it is an indication of its intended and use
microscopy most often used for fibre examination
polarised light microscope
- Many dyes used to colour textiles have fluorescent components and these respond to certain wavelengths of light in fluorescent microscopy
delustrants
are finely ground particles of materials such as titanium dioxide that are introduced into the spinning dope to help diffract light passing through the fibres an reduced embossed are
