0. Chapter 5
Chapter 5: Hair
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1. Chapter 5
forensics_human_hairs_identi.htm
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2. Hair Analysis hair is class evidence
Chapter 5
Hair Analysis
hair is class evidence
hair can be used to back up circumstantial evidence
hair absorbs and adsorbs substances both from within the body and from the external environment
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3. After this unit you should be able to:
Chapter 5
Hair Analysis
After this unit you should be able to:
Describe the structure of a hair
Explain the difference between human and animal hair
Explain which characteristics of hair are important for forensic analysis
Assess the probative value of hair samples
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4. 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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5. The Biology of Hair
An appendage of the skin that grows out of an organ known as the hair follicle.
Extends from its root or bulb embedded in the follicle, continues into a shaft, and terminates at a tip end.
Hair follicle: sac-like anatomical structure from which hair grows. Sebaceous gland: gland that secretes sebum, which lubricates the skin and hair. Arrector pili muscle: muscle that elevates the hair. Root of hair: part of the hair implanted in the dermis. Papilla: part of the hair connected to the conjunctival tissue. Inner root sheath: sheath formed of several layers of cells. Connective tissue sheath: girdle enclosing the epithelial sheath and connecting to the conjunctival tissue. Epidermis: outer layer of the skin. Hair shaft: a filament that grows from the skin.

6. Chapter 5
Skin Structure
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7. Hair Shaft Cuticle—outside covering, made of overlapping scales
Chapter 5
Hair Shaft
Composed of:
Cuticle—outside covering, made of overlapping scales
Cortex—inner layer made of keratin and imbedded with pigment; also contains air sacs called cortical fusi
Medulla—inside layer running down the center of the cortex
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8. 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 between species of animals and are named based on their appearance. The three basic patterns are:
Coronal
Spinous
Imbricate
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9. Cuticle Patterns
Coronal or crown-like scale pattern, is found in hairs of very fine diameter and resemble a stack of paper cups. Coronal scales are commonly found in the hairs of small rodents and bats but rarely in human hairs.
Spinous or petal-like scales are triangular in shape and protrude from the hair shaft. They are found at the proximal region of mink hairs and on the fur hairs of seals, cats, and some other animals. They are never found in human hairs.
Imbricate or flattened-scale type consists of overlapping scales with narrow margins. They are commonly found in human hairs and many animal hairs

10. Human Scales In order to visualize the Scales we will:
Chapter 5
Human Scales
In order to visualize the
Scales we will:
paint clear fingernail polish on a glass slide
when the polish begins to dry, place a hair on the polish
when almost dry, lift off the hair and observe the scale imprints
What pattern is seen in
this slide?
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11. 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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12. 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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13. Human medulla may be continuous, fragmented or absent.
Chapter 5
Human Medulla
Human medulla may be continuous, fragmented or absent.
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14. Chapter 5
Medullary Index
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.
mouse
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15. 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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16. Comparison of Animal and Human Hair
Humans
Animals
Medullary Index ≥1/2
Medulla is present for all animals
Medulla is continuous for most animals
Medulla is patterned for most animals
Medullary Index <1/3
Medulla is absent for most humans
Medulla is continuous for Mongoloid race
Medulla is fragmented: only some animals and humans
Medulla is cylindrical in shape (most animals)

17. Hair Growth Terminology
Chapter 5
Hair Growth
Terminology
Anagen: hair that is actively growing; lasting up to 5 years
Catagen: hair is not growing; a resting phase
Telogen: hair that is dying and ready to fall out; lasting two to six months
Grows about 0.5 mm per day or 1 centimeter per month; approximately one half inch per month
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18. Chapter 5
The Root
Human roots look different based on whether they have been forcibly removed or if they are telogen hairs and have fallen out. Animal roots will vary, but in general have a spear shape.
Fallen out
Forcibly removed
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19. Hair Comparison Color Length Diameter
Chapter 5
Hair Comparison
Color
Length
Diameter
Distribution, shape and color intensity of pigment granules
Dyed hair has color in cuticle and cortex
Bleaching removes pigment and gives a yellow tint
Scale types
Presence or absence of medulla
Medullary type
Medullary pattern
Medullary index
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20. What causes gray hair?
As you age, your natural production of pigment slows down and your natural color loses its color strength.
This doesn't happen to every hair at the same time, so the contrast between the hair with no color and the hair that still has some color causes it to look gray.
So how gray your hair actually looks is determined by the percentage of strands with no color vs. the pigmented strands.

21. Chapter 5
DNA from Hair
The root contains nuclear DNA. If the hair has been forcibly removed, some folicular tissue may be attached containing DNA.
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 costly than using nuclear DNA.
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22. 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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23. 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 of poisoning.
Collections must be taken from different locations on the body to get an accurate timeline.
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24. Chapter 5
Hair Toxicology
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 did him in.
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25. Chapter 5
More about Hair
For additional information about hair and other trace evidence, check out Court TV’s Crime Library at:
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26. Chapter 5
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