1. Hair

2. Learning Objectives
Recognize and understand the cuticle, cortex, and medulla areas of hair
List the three phases of hair growth
Appreciate the distinction between animal and human hairs
List hair features that are useful for the microscopic comparison of human hairs
Explain the proper collection of forensic hair evidence
Describe and understand the role of DNA typing in hair comparisons

3. Hair
Hair is encountered as physical evidence in a wide variety of crimes.
Although it is not yet possible to individualize a human hair to any single head or body through its morphology, it still has value as physical evidence.
When properly collected and submitted to the laboratory accompanied by an adequate number of standard/reference samples, hair can provide strong corroborative evidence for placing an individual at a crime scene.

4. HAIR
Hair is an appendage of the skin that grows out of an organ known as the hair follicle.
The length of a hair extends from its root or bulb embedded in the follicle, continues into a shaft, and terminates at a tip end.
It is the shaft, which is composed of three layers—the cuticle, cortex, and medulla—that is subjected to the most intense examination by the forensic scientist.
FYI: There are about 100,000 scalp hairs on the average person

6. Analogy: Hair is Like a Pencil
How is the morphology of a hair like that of a pencil?
Eraser is the Root
Paint is the Cuticle
Wood is the Cortex
Lead is the Medulla

7. Cuticle
Cuticle: the scale structure covering the exterior of the hair.
The scales always point towards the tip of the hair.
The scale pattern is useful in species identification.

8. Cuticle Scales of most animal hair are like shingles on a roof.
Variety of patterns are important in species identification.
Viewed through scanning electron microscope
Make a cast of surface
Embed hair in a soft medium (clear nail polish or softened vinyl)
and let harden
Remove hair and an impression of cuticle will be
left behind
Ideal for examination under a microscope

9. Coronal Cuticle

10. Imbricate Cuticle

11. Spinous Cuticle

12. Dog Hair Human Pubic Hair
Deer Hair
Cat Hair
Mouse Hair

13. Cortex Cortex: the main body of the hair shaft
Contained within the protective layer of the cuticle.
Forensic Importance: embedded with pigment granules that impart hair with color.
The color, shape, and distribution of these granules provide the criminalist with important points of comparison among hair of different individuals

14. Pigment Granules are Absent in Grey Hair
←brown
red→
Pigment Granules are Absent in Grey Hair

15. Medulla
Medulla: a cellular column running through the center of the hair.
The medullary index measures the diameter of the medulla relative
to the diameter of the hair shaft.
For humans, the medulla generally occupies less than one-third
the diameter of the shaft, while for animals it is generally one-half or greater.
The medulla may be continuous, interrupted, fragmented, or absent.
The presence of the medulla varies from individual to
individual and even among hairs of a given individual.
Medullae also have different shapes, depending the species.

17. Medulla
Human head hairs generally have no medulla or have fragmented ones
Most animals have medullae that are either continuous or interrupted
An interesting feature of the medulla is its shape:
Humans and many animals have medullae that give a nearly cylindrical appearance
Other animals exhibit medullae that have a patterned shape
Cat: string of pearls
Deer: spherical cells that occupy entire hair shaft

18. Root
Provide the tools necessary to grow hair and continue its growth (along with other surrounding cells contained within the hair follicle)
Human head hair grows in three developmental stages and the shape and size of the hair root is determined by the growth phase in which the hair happens to be.
Anagen Phase
Catagen Phase
Telogen Phase

19. Anagen Phase
The initial growth phase during which the hair follicle actively produced hair.
May last up to 6 years
The root is attached to the follicle for continued growth, giving the root bulb a flame-shaped appearance
When pulled from the root, some anagen hairs will have a follicular tag – a translucent piece of tissue surrounding the hair’s shaft near the root; it contains the richest source of DNA associated with hair!

20. Catagen Phase
A transition stage between the anagen and telogen phases of hair growth.
Hair continues to grow during this phase, but at a decreasing rate
Lasts 2-3 weeks
Roots take on an elongated appearance as the root bulb shrinks in size and is being pushed out of the hair follicle

21. Telogen Phase
The final growth phase in which hair naturally falls out of the skin.
Once hair growth ends, the telogen phase begins and the root takes on a club-shaped appearance
During a 2 to 6 month period the hair is pushed out of the follicle causing the hair to naturally shed
FYI: Most people lose about 100 scalp hairs a day

22. Identification and Comparison of Hair
When hair evidence is present in a criminal case the prime purpose for its examination is:
To determine if it is human or animal in origin
Scale structure, medullary index, and medullary shape are features that are important in hair identification
To determine whether human hair retrieved at a crime scene compares with hair from a particular individual
In making a hair comparison, a comparison microscope is an invaluable tool
Allows the examiner to view both hairs side-by-side
Because hair from any part of the body exhibits a range
of characteristics, it is necessary to have an adequate
number of known hairs

23. Characteristics of Hair used for Comparison Purposes
Color
Length
Diameter
Presence or absence of medulla
Distribution, shape, and color intensity of pigment granules present in the cortex
Dyed or bleached (from natural)
Dyed: color present in cuticle and throughout cortex
Bleaching: remove pigment and gives it yellowish tint
Grows about 1 cm/month, therefore the time from the last dyeing or bleaching can be estimated
Abnormalities due to diseases or deficiencies
Presence of fungal and nit infections

24. Uses of Hair at Crime Scene
Vernon J. Gerberth, in Practical Homicide Investigation, points out that hair (and fiber) evidence is useful in:
Helping to establish the scope of the crime scene
Placing a perpetrator at a scene
Connecting a suspect with a weapon
Supporting witness statements
Connecting crime scene areas (abduction, vehicle used, dump site)

25. Questions Concerning Hair Examination
Can the body area from which a hair originated be determined?
Can the racial origin of hair be determined?
Can the age and sex of an individual be determined from a hair sample?
Is it possible to determine if a hair was forcibly removed from the body?
Are efforts being made to individualize human hair?
Can DNA individualize a human hair?

26. Collection of Hair Evidence
As a general rule, forensic hair comparisons involve either head hair or pubic hair.
Imperative that the questioned and standard/reference hairs come from the same area of the body
The collection of 50 full-length hairs from all areas of the scalp will normally ensure a representative sampling of head hair.
A minimum collection of two dozen full-length pubic hairs should cover the range of characteristics present in pubic hair.
Hair samples are also collected from the victims of suspicious deaths during an autopsy.

27. Can the Body Area of a Hair be Determined?
This task is relatively simple.
Scalp Hairs
show little diameter variation
have a more uniform pigment color
Pubic Hairs
short and curly
wide variation in shaft diameter
usually have continuous medullae
Beard Hairs
coarse
triangular cross section
blunt tips from cutting and shaving

28. Can the Age and Sex of a Hair be Determined?
Age cannot be learned with any degree of certainty except with infant hairs, which are short, fine, have fine pigment, and are rudimentary in character.
The presence of bleaches and dyes may play a role in the determination of gender; however, these characteristics are less valuable than they were in the past
Recovering nuclear DNA from tissue adhering to the hair or from the root structure of the hair will allow for determination of gender.

29. Can the Racial Origin of Hair be Determined?
African Head Hair
Normally kinky
Contains dense, unevenly distributed pigments
Cross section is flat to oval
Caucasian Head Hair
Usually straight or wavy
Fine to coarse pigments that are more evenly distributed
Cross-section is oval to round
All of these observations are general in nature, with many possible exceptions.

30. Is it Possible to Determine if Hair was Forcibly Removed?
Examine Hair Root
Pulled Hair: if follicular tissue is present the hair was probably pulled out by another person or by brushing or combing
Natural Fall Out: if the root is bulbous-shaped with no adhering follicular tissue

31. Are Efforts Being Made to Individualize Human Hair?
Nuclear DNA
DNA present within the nucleus of a cell; this form of DNA is inherited from both parents
Forensic hair examiners can link human hair to a particular individual by characterizing the nuclear DNA present in the hair root or the follicular tag
With no follicular tag present, the examiner must extract DNA from the hair root
Higher rate of success extracting DNA during the anagen phase or from hairs entering the catagen phase (telogen phase hairs have an inadequate mount of DNA to successfully type)

32. Are Efforts Being Made to Individualize Human Hair?
Mitochondrial DNA
DNA present in small structures (mitochondria) outside the nucleus of a cell. Mitochondria are responsible for supplying energy to the cell. This form of DNA is maternally inherited.
There are many more copies of mitochondrial DNA located in our cells as compared to nuclear DNA
The success rate for finding and typing mitochondrial DNA is much greater from hair because it has limited quantities of nuclear DNA
As a rule, all positive microscopical hair comparisons must be confirmed by DNA analysis.