Hair Flashcards
Why is hair a great form of trace evidence?
It’s found on all humans and other mammals
It’s constantly being produced & shed in their immediate environments
It’s highly stable, resisting both physical and chemical degradation
It’s easily overlooked by criminals involved in nefarious activities
It’s **readily transferred **from one person/object to another person/object
Hairs from different individuals can be distinguished from each other, and with DNA testing
Information from the examination of hairs can provide **investigative leads **or help with the reconstruction of events in contention
What is hair made of?
Hairs are composed primarily of protein, specifically keratins
these can persist for thousands of years and remain unchanged.
Why is it impractical to differentiate between hairs?
Because they all have the same basic chemistry
How can hair serve an aid in crime reconstruction?
Looking at isotope ratios in the hair can be used to identify locations where an individual may have travelled based on changes in drinking water isotopes in different locations
can track drugs or elements in substance abuse =
What are the three types of hairs?
Lanugo - hair formed in the uterus, fine and pigmented and shed before birth
Vellus - fine, short, pigmented hair. Found on noses, ears and forehead
Terminal hair - hairs that are macroscopically visible.
What is terminal hair categorised into?
primary hairs - hair on head, eyelashes, and eyebrow
secondary hair - pubic, underarm, beard
What are the three main histological layers of hair?
Cuticle - Outermost layer of hair. This is largely responsible for the chemical resistance of hair
Cortex - Main bulk of hair. This is largely responsible for the mechanical properties of hair (flexibility, strength)
Medulla - Innermost layer of hair shaft. Not very well studied or understood and is not found in all hairs.
The cell membrane complex binds all cells together
the follicle is where the hair grows from, and it changes size and shape throughout the hair cycle.
What is the hair cycle?
Anagen - Active growing phase of hair extending progressively from the the follicle root outwards from skin
Catagen - Transition phase when growth slows and eventually stops
Telogen - Resting phase when minimal force is required to remove hair and natural shedding (exigent) likely to occur
How does hair “turn grey”?
Hair doesn’t turn grey, pigment stops being produced, giving the appearance of white/grey.
How is hair recovered?
Use forceps for the collection of individual hairs.
Be careful not to damage hair with too much pressure (bulging)
Use a tape lift, less precise but maintains the integrity
use a comb and pluck them out
ENFSI - Collect 20 hairs from 5 different head regions to have a representative sample due to the inherent variation.
What is the analytical workflow for hair?
Gross examination, recovery and collection
Preliminary evaluation of physical characteristics
Microscopic Techniques
(DNA)
SEM (Very occasionally TEM)
Spectroscopic Techniques - IR & Raman
Chromatographic Techniques & Mass Spectrometry
What morphological characteristics of hair are we looking for using a stereoscopic microscope?
Macroscopic colour - colourless, blonde, black and brown
Length - measure in absolute units (mm)
Appropriate diameter - thin, medium, thick
General contour and curliness e.g straight, wavy, curly
you can use a stereoscopic microscope
What morphological characteristics of hair are we looking for using a compound light microscopy?
Compound light microscopy
colour - colourless, black, brown, blonde
Cosmetic procedures - bleached or dyed
Thickness range (in micrometers)
Cross sectional shape e.g round, oval, flattening
Shaft irregularities - buckling or twisting
General damage - crushed, burnt, frayed, broken
Biological damage - fungal or bacterial damage
Adhering material - particles, nits, particles
Non-root morphologies
What are microscopic features of the cuticle?
Colour
Pigment granules
Thickness
Damage
Inner margin - smooth or cracked
Scale protrusion
What are microscopic features of the cortex?
Pigment granules - density, size, shape and distribution, aggregates
Texture - fine, medium, coarse
Cortical fusi or Ovoid bodies
