Difference due to:
- Somantic Origin
- Cosmetic Treatment
Cuticle = Outside surface of hair
Cortex = Major part of hair mass
Pigment = contained within cortex - defines colour
Medulla = At centre of shaft, within cortex - normally filled with air and increases hair strength
Distal Terminus = tip of hair
Proximial Terminus = root of hair
- Layer of cells - outer surface of hair
- Cells overlap with free ends pointing towards distal terminus
3 types of cuticle
- Coronal (Crown-like) - rarley human (Rodent, bats, cats)
- Spinous (petal-like) - NEVER human (Seal, cats other mammals)
- Imbricate (flattened) - Human (and a few other animmals)
If Medullary Index (MI) less than or equal to 1/3 = human
If MI greater than 1/2 = animal
DISTAL TERMINUS - can tell how hair was cut and time since last treatment.
PROXIMAL TERMINUS - can tell how hair was shed, naturally or mechanially?
Can change colour, shape and chemistry of hair
Whole Fibre Treatment:
Hair as Physical Evidence
Ideal physical evidence: -
- Significant amounts are lost unwittingly.
- Hair is chemically quite stable.
- DNA evidence can be obtained from a single hair providing individualisation of the sample.
Need to determine:
Species - human or animal?
Geographical Origin - Race
Somatic Origin - from where on body?
Somatic Origin 1
- Vary in length
- Tips often cut or split and rarely tapered
- Diameter varies very little along length
- Shorter, curlier, flatter cross section
- Continuous medulla
- Finer and lighter in colour
- Slight Pigmentation
- 3-6mm in length
Somatic Origin 2
- Short curved with tapared tips
- Large Medulla
- Relatively Coarse
- Stiff texture
- Moderate diameter variation
- Tapered Tips
- Small Diamete than pubic hairs