Ms Clark 2014 PVMHS Hair evidence What information can be gained from analysis of hair Hair alone without follicle cells is trace evidence amp class evidence It does not identify a specific individual but can narrow your suspects down based of certain characteristics of their h ID: 481911
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Slide1
The Study of Hair
Ms Clark, 2014
PVMHSSlide2
Hair evidence
What information can be gained from analysis of hair?
Hair alone (without follicle cells) is
trace evidence
&
class evidence
.
It does not identify a specific individual, but can narrow your suspects down based of certain characteristics of their hair.Slide3
Hair evidence
Hair is easily left behind at a crime scene.
Adheres easily to carpet, clothes, and many other surfaces (sheets, blankets, car interior, moist surfaces).
Hair has a tough outer coating and does not decompose easily, so it’s durable.
Hair can be analyzed to determine race, history of drug use, evidence poisoning/toxins, nutritional deficiencies.
Hair analysis can sometimes indicate what water supply a person is using!Slide4
History of Hair Analysis
1883: Alfred
Swaine
Taylor and Thomas Stevenson publish
The Principles and Practice of Medical Jurisprudence
and include a chapter on using hair in forensic investigations.
1910: Victor Balthazar &
Marcell
Lambert (French forensic scientists) publish
Le
Poil
de
l
’Homme
et des
Animaux
(the hair of man and animals) which includes microscopic studies of hair from most mammals.
1934: Dr. Sydney Smith uses a comparison microscope to perform side-by-side analysis of hairs collected from a crime scene.
Today hair analysis includes neutron activation analysis (NAA) , chemical analysis, and DNA analysisSlide5
The Function of Hair
Why do mammals (including humans) have hair?Slide6
The Function of Hair
Helps to regulate body temperature
What happens when you get cold? Why?
Protects the skin against sunlight
Acts as a sensory organ
When hair is very dense, it’s called fur.Slide7
The Structure of Hair
Hair originates from the skin.
Your skin is known as the Integumentary system.
Hair is an “accessory organ” to your skin.
The skin has 3 layers:
Epidermis (most superficial layer, at the surface)
Dermis (middle layer)
Hypodermis (deepest layer)Slide8
The Structure of Hair
Hair originates from the hair bulb, is surrounded by the hair follicle, and is located in the
dermis
.
The end of the follicle is called the papilla
, this is where the blood vessels meet the hair to supply nutrients
.Slide9
The Structure of Hair
(Generally) a sebaceous gland (oil gland) is associated with each hair bulb.
Helps water proof the hair and protect it from drying out.
A muscle that attaches to the hair follicle to erect the hair when stimulated (cold or scared).
The hair shaft is what you see (the hair on your arm or on your head).Slide10
The Structure of Hair
The cuticle of the hair is composed of
keratin
,
a protein produced in the skin.
Proteins are made up of chains of amino acids that are connected by strong bonds, making hair strong and flexible.Slide11
The Structure of Hair
The hair shaft is made up of 3 layers: the medulla, the cortex, and the outer cuticle.
Pencil analogy:
-Central medulla
-Cortex surrounds
medulla
-Cuticle on outsideSlide12
The Cuticle
The outer layer of the hair shaft, made up of keratin.
The scales point away from the scalp.
This can indicate where the “younger” part of the hair is (closest to the scalp).
Useful when looking for drugs or toxins at a specific point in time.Slide13
The Cuticle
Humans have scales that are flattened and narrow, called
imbricate
scales.
Some animals have hair with different scales, this allows scientists to distinguish human hair from animal hair.
Coronal
scales have the appearance of a stack of crowns.
Spinous
scales resemble petals.Slide14
Imbricate - Human
Spinous
- cats
Coronal - rodentsSlide15
The Cortex
Contains most of the pigment granules, called
melanin
. This gives the hair its color.
Pigment distribution varies from person to person
Some people have larger pigment granules, giving a more uneven distribution when viewed under a microscope.Slide16
The Medulla
The center of the hair is called the medulla.
There are different patterns that a person could have
Continuous
Interrupted
Fragmented/segmented
Solid
Absent
There is also significant differences between species.Slide17
Medulla patternsSlide18
Variation in Hair
Shape: hair may be circular, triangular, flattened, or irregular.
Length
Color: depends on distribution of pigment granules.
Human hair is usually one color along the entire length unless it has been artificially dyed.
Animals often have pigments found in solid masses called
ovoid bodies
, this is why the color of animal hair can appear banded.Slide19
Variation in Hair
Texture:
Vibrissa – the whiskers of many animals
Bristle – coarse hair that provides a protective coat
Wool – fine hairs that cover the bodies of mammals and protect from wet & cold
Diameter: The ratio of the diameter of the medulla to the diameter of the hair is called the
medullary
index
.
Animals have a greater
medullary
index than humans.Slide20
Human Hair
Head and body hair of humans is intermediate combining the characteristics of bristle and wool.
4 types:
Primordial hairs
– appears in 3
rd
month of gestation
Lanugo hairs
– replaces the primordial hairs, appears around the 5
th
month of gestation and are generally shed by the 8
th month of gestation.Vellus hairs
– soft hairs spread uniformly all over the body
Terminal hair
– found on the scalp, eyebrows/eyelashes, limbs/body, pubic, & axillary regions.Slide21
Life Cycle of Hair
Hair proceeds through 3 stages as it develops.
Anagen
stage: Period of active growth when cells around the follicle are rapidly dividing.
Lasts 2-6 years on the scalp, but may be less on other areas of the body.
Canagen
stage: Period of transition, hair follicle shrinks & papilla detaches
Telogen
phase: Follicle remains dormant, eventually hair will loosen and fall out and the
anagen
stage begins again.Slide22
Hair as evidence
Review
Locard’s
exchange principle
Whenever 2 objects come in contact, some transfer of material will occur.
Hair is trace evidence
Hair can be collected by plucking, shaking, placing tape over a surface, using a special vacuum.
If a large number of hairs are collected from a crime scene the technician has to compare the hairs from the crime scene to hairs from the victim and/or suspect.Slide23
Hair analysis
Can be analyzed macroscopically and microscopically.
Macroscopic analyses include length, color, texture, curliness.
Microscopic analyses include medulla pattern, cortex pigmentation, type of scales on the cuticle, and medullary index.Slide24
Hair analysis
Many dyes will fluoresce under certain types of light.
Chemical tests can be used to determine presence of toxins or drugs.
If hair is forcibly removed the hair follicle may be present.
This is known as a
follicular tag
.
Blood and tissue attached to the tag may be analyzed for blood type and DNA analysis.Slide25
Chemical analysis
By testing different parts of the hair it’s possible to establish a timeline for when exposure to poisons or other toxins occurred.Slide26
Chemical analysis
Hair grows about 1.3 cm per
month
if
a toxin occurs at 9cm from the root, you would divide by 1.3 to get the approximate time that the exposure occurred.Slide27
Chemical analysis
Neutron Activation Analysis (NAA) can be used to identify up to 14 elements in a single 2cm strand of hair.
Including: antimony, argon, bromine, copper, gold, manganese, silver, sodium, arsenic, chlorine, and zinc
The probability of 2 hairs
having
the same profile is very low.Slide28
Any questions?