1. Chapter 5
Hair
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2. Chapter 5
Introduction
Human hair is one of the most frequently found pieces of evidence at the scene of a violent crime. It can provide a link between the criminal and the crime.
From hair, one can determine:
If the source is human or animal
Race (sometimes)
Origin of the location on the source’s body
Whether the hair was forcibly removed
If the hair has been treated with chemicals
If drugs have been ingested
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3. Chapter 5
Skin Structure
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4. Hair is only found in mammals
Hair is only found in mammals. Hair is made of epidermal cells that grow out of follicles. In the follicle, hair is nourished by blood vessels.
Keratin is a protein (also found in fingernails) that gives hair its hard durable structure.
Hair grows about ½ inch per month so you can tell when certain drugs were ingested (e.g. THC from marijuana)
Melanocytes: cells that make pigment called melanin. Dark hair has more melanin. Gray hair has lost its melanin

5. Hair Shaft Composed of:
Chapter 5
Hair Shaft
Composed of:
Cuticle—outside covering, made of overlapping scales
Cortex—inner layer made of keratin and embedded with pigment; also contains air sacs called cortical fusi
Medulla—inside layer running down the center of the cortex
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7. Chapter 5
The Cuticle
The cuticle is the outermost layer of hair which is covered with scales. The scales point toward the tip of the hair. Scales differ among species of animals and are named based on their appearance. The three basic patterns are:
Coronal
Spinous
Imbricate
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8. Human Scales In order to visualize the scales:
Chapter 5
Human Scales
In order to visualize the
scales:
Paint clear fingernail polish on a glass slide.
When the polish begins to dry, place a hair on the polish.
When it is almost dry, lift off the hair and observe the scale imprints.
What pattern is seen in this slide?
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9. The Cortex The cortex gives the hair its shape.
Chapter 5
The Cortex
The cortex gives the hair its shape.
It has two major characteristics:
Melanin—pigment granules that give hair its color
Cortical fusi—air spaces, usually found near the root but may be found throughout the hair shaft
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10. Chapter 5
The Medulla
The medulla is the hair core that is not always visible. The medulla comes in different types and patterns.
Types:
Intermittent or interrupted
Fragmented
Continuous
Stacked
Absent—not present
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11. Human medulla may be continuous, fragmented, or absent.
Chapter 5
Human medulla may be continuous, fragmented, or absent.
Animal hair medullas:
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12. Fur Hairs: are fine, soft, kinked and closely spaced.
Non-Human Hair
Guard Hairs: form outer coat and are usually course, straight, and taper to a point.
Fur Hairs: are fine, soft, kinked and closely spaced.
Whiskers: are long, thick and stiff
Deer
Mouse

13. Chapter 5
Medullary Index
Mouse
Determined by measuring the diameter of the medulla and dividing it by the diameter of the hair.
Medullary index for human hair is generally less than 1/3.
For animal hair, it is usually greater than 1/2.
Human
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14. Chapter 5
Hair Shape
Can be straight, curly, or kinky, depending on the cross-section, which may be round, oval, or crescent-shaped.
Round
(Straight)
Oval
(Curly)
Crescent moon
(Kinky)
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15. Hair Growth Anagen—hair is actively growing; lasts up to 5 years
Chapter 5
Hair Growth
Anagen—hair is actively growing; lasts up to 5 years
Catagen—hair is not growing; a resting phase
Telogen—follicle is getting ready to push the hair out; lasts
two to six months
Hair grows about 0.4 mm per day, or 1 cm per month
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16. The process of hair growth has three phases:
Hair Cycle
The process of hair growth has three phases:
Anagen: This is the active growth stage of the hair fiber and can last from 2- 7 years. At any given moment 80-85% of our hair is in the anagen phase.
Catagen: Sometimes referred to as the transitional phase, which is when hair growth begins to “shut down” and stop activity. It generally lasts days.
Telogen: This occurs when hair growth is completely at rest and the hair fiber falls out. At any given time, % of our hair is in the telogen phase, which generally lasts 100 days for scalp hair. After the telogen phase, the hair growth process starts over again to the anagen phase.

17. Chapter 5
The Root
Human roots look different based on whether they have been forcibly removed or they are telogen hairs and have fallen out. Animal roots vary, but in general have a spear shape.
Fallen out
Forcibly removed
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18. Chapter 5
DNA from Hair
The root contains nuclear DNA. If the hair has been forcibly removed, some follicular tissue containing DNA may be attached.
The hair shaft contains abundant mitochondrial DNA, inherited only from the mother. It can be typed by comparing relatives if no DNA from the body is available. This process is more difficult and more costly than using nuclear DNA.
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19. Chapter 5
Collection of Hair
Questioned hairs must be accompanied by an adequate number of control samples.
From victim
From possible suspects
From others who may have deposited hair at the scene
Control sample
50 full-length hairs from all areas of scalp
24 full-length pubic hairs
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20. Hair Toxicology Advantages:
Chapter 5
Hair Toxicology
Advantages:
Easy to collect and store
Is externally available
Can provide information on the individual’s history of drug use or evidence of poisoning
Collections must be taken from different locations on the body to get an accurate timeline.
Napoleon died in exile in By analyzing his hair, some investigators suggest he was poisoned by the deliberate administration of arsenic; others suggest that it was vapors from the dyes in the wallpaper that killed him.
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21. Hair Damage
Cuticle, the outer layer of the hair shaft, defines smoothness and shininess. The hair cuticle may get damaged by chemical processes, overexposure to sunlight (UV rays), too much heat from a dryer, abusive brushing and combing, over-chlorinated swimming pool water, etc.
Damaged hair/cuticles should be treated well with conditioners because cuticles cannot repair themselves once damaged.
     
Split End

22. Hair Raising Facts:
An average scalp has 100, ,000 hairs (about 1000 per square inch)
Hair is so strong that each hair can withstand the strain of 100 grams (3.5 ounces). An average head of hair could hold tons if only the scalp was strong enough!
Human hair grows autonomously, that is each hair is on its own individual cycle. If all our hair were on the same cycle, we would molt!
Hair has the highest rate of mitosis (cell division). An average hair grows 0.3 mm a day and 1 cm per month. 35 meters of hair fiber is produced every day on the average adult scalp.
Less than 4% of the world’s population has naturally red hair
Most people lose between hairs per day
Over 50% of men by age 50 have male pattern hair loss.
Forty percent of women by the time they reach menopause will have female pattern (hereditary) hair loss.
Hormone imbalance and crash dieting can trigger temporary hair loss.

24. Chapter 5
More about Hair
For additional information about hair and other trace evidence, check out truTV’s Crime Library at:
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