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.
