1. Hair Evidence
Forensic Science
Mr. Glatt,

2. The average human has approximately 250,000 hairs that get replaced in a 3 year cycle.
About 250 hairs are shed daily; about 100
being from the head.
Blondes tend to have more head hairs than brunettes. Red heads have the least.

3. Function of Hair All mammals have hair Functions of hair include
Body temperature regulation and warmth
UV protection
Decrease Friction
Helps with sense of touch

4. Hair as Evidence
Hair is considered class evidence when the hair follicle is not attached
Investigators can identify a subgroup or class of people who share similar hair characteristics
Useful in determining whether to include or exclude someone as a suspect
When follicle is attached it becomes individualized evidence because DNA can be obtained
Skin cells and blood on follicle provide DNA
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5. Hair as Evidence, cont…
Hair is easily transferrable from crime scenes because it adheres to fabrics in clothes, carpets, ect…
It can be transferred from victim/suspect, this is called direct transfer
It often is transferred to other locations, this is called secondary transfer
Secondary transfer is especially common with pet/animal hair
Chemical testing of hair can also provide a history of the use of drugs and other toxins, indicate the presence of heavy metals, and even provide an assessment of nutritional deficiencies z

6. The Structure of Hair Hair Follicle
Hair Consists of two Parts
Hair Follicle- club shaped structure that extends into the dermal layer of skin
Generates hair shaft
Sebaceous (oil) glands condition hair with oils
Blood vessels at end for growth, repair

7. The Structure of Hair Shaft
Composed dead cells filled with 2 proteins
Keratin is what gives hair it’s strength
Melanin is what gives hair it’s pigmentation or color

8. 3 LAYERS OF HAIR SHAFT MEDULLA, CORTEX, AND CUTICLE

9. 3 Layers of Hair Shaft The Medulla
–Medulla is the inner most layer
• Central canal or tube that may or may not be filled with dead cells
• Forensic Scientists can classify hair into 5 different groups based on the appearance of medulla
• TYPES OF MEDULLA/MEDULLA PATTERN S BELOW:

10. 3 Layers of Hair Shaft The Cortex
-Cortex- middle and thickest layer of hair shaft
Contains most of the melanin or pigment granules that gives hair its color
Amount of pigment varies from person to person
-based on inheritance
Some people have more melanin or pigment granules which gives an uneven appearance under the microscope

11. 3 Layers of Hair Shaft The Cuticle
Transparent outer layer of the hair; protects the hair.
composed of protein keratin which gives strength and flexibility to hair
Made of scales that overlap one another and point toward the tip end
Characteristics of the cuticle may be important in distinguishing between hairs of different animals but are often not useful in distinguishing between different people.

12. Spinous, or “spike– like.” Never found in humans.
3 Cuticle Types
Spinous, or “spike– like.” Never found in humans.
Common in cats, seals, and minks ect...
Coronal, or “crown – like.” Found in hairs of very fine diameter.
Typical of mice and other rodents.
Sometimes humans
Imbricate, flattened and narrow.
HUMANS and some other animals

13. Examination of Hair Macroscopic
Without microscope
Length -shape (cross section)
width
Color
Curliness

14. Examination of Hair Microscopic
Microscopes and other devices can give finer details
Indicate fine detail in hair structure such as:
dyed or other treatment
Type of medulla/medullary index
Pigmentation in cortex
cuticle type

15. Hair viewed for forensic investigations is studied both macroscopically and microscopically
Different kinds of microscopes provide different kinds of evidence.
Comparison microscopes are especially important tools to the forensic investigation of hair.
A fluorescence microscope is equipped with filters to detect fluoresced light, indicating the presence of a dye or other treatment.

16. Electron microscopes provide incredible detail of the surface or interior of the sample, magnifying the object 50,000 times or more.

17. What can hair samples can tell us?
Whether the source is animal or human
Racial origin (sometimes)
Location on the sources body
Whether the hair has been chemically treated (dyed, permed, straightened)
Color and pigmentation
Presence of toxins or drug metabolites
Whether the hair was forcibly removed
–If so, follicle usually still attached

18. Animal vs Human Hair Medullary Index
Medullary Index is of diameter of medulla to diameter of entire hair shaft
Divide diameter of hair shaft by diameter of entire hair shaft
Humans .33 or less, Animals .50 or more
Medulla Types- Distinct Differences

19. Animal vs Human Hair Other Differences Pigmentation:
animal hair is denser toward the medulla
human hair tends to be denser toward the cuticle
Banded Color Patterns:
possible in animals
not in humans, COLOR STAYS THE SAME THROUGHOUT, unless it’s been altered

20. How hairs differ
SHAPE- A cross section: circular, triangular, irregular, or flattened
–Shape influences the curl of the hair
TEXTURE- coarse or fine
COLOR-blonde, brown, black, red ect…
Hairs can differ, even hairs from the same parts of the body
–Distribution of Melanin (pigment granules)
Hair From Different Parts of Body

21. Human hair varies on the body
* one way to distinguish is by cross-section
* other ways to distinguish as well
– Head
Usually circular or oval
Little variation in humans and more uniform distribution of pigment
– Eyebrows & Eyelashes
Circular and often have tapered ends

22. Beard and Mustache Tend to be thick and triangular
course and may have double medulla
Blunt tips from cutting or shaving

23. Underarm
– Body Hair
•Oval or triangular
• Blunt tip or may be frayed from abrasion
– Pubic
• buckling may be present, short and curly
• Diameter may vary greatly

24. Treated Hair • Bleaching –disturbs the scales on the cuticle and
–removes melanin (pigment)
–leaves hair brittle and yellowish
• Dyeing colors the cuticle and the cortex

25. Racial Differences
• Broad, racial groups do exhibit some shared physical characteristics
• But NOT applicable to all individuals in these groups
–Therefore,
•Individual hairs CANNOT necessarily be assigned to any of these groups
• Age Determination
• Age can not be determined with any degree of certainty except for infant hair
– Infant hairs are fine, short in length, and have fine pigment

26. Collecting Hair as Evidence
Recover all hair present.
Use the fingers or tweezers to pick up visible strands of hair when possible. Tape lift may be used to help collect hairs if needed. When surfaces are large, they can also be vacuumed.
Place hair in paper bindles or coin envelopes which should then be folded and sealed in larger envelopes. Label the outer sealed envelope.

27. Using Hair in an Investigation
• Hairs must come from same area of the body
–Comparisons must be made from same location of the body
• Hairs from even the same part of the body can differ
• Forensic hair comparisons generally either involve either head hair or pubic hair
–Head hairs- 50 full length hairs should be taken for comparison to hair in question
–Pubic haris- 25 full length hairs should be taken for comparison to hair in question

28. Microscopic Examination Potential Error
• Microscopic comparison of hair has long been accepted practice as approach to including or excluding suspects
– Can be subjective and is highly dependent of skills and integrity of analyst, and hairs being examined
– Before DNA it was relied upon more
• FBI study conducted from
–a number of microscopic matches were shown incorrect when samples were subjected to DNA testing (about 11%)

29. Testing the Hair Follicle
If hair is forcibly removed the entire hair follicle may be present along with very small amounts of
–Blood can be typed to determine blood type
*Still class evidence
DNA from follicle cells and hair root can be analyzed
individualized evidence
Often times microscopic analysis is completed first to determine if is a possible match, more cost effective

30. Mitochondrial DNA in Shaft
• Hair in shaft contains no nuclear DNA
• Hair in shaft does contain mitochondrial DNA
– Mitochondrial DNA passed down from mother, originates from mitochondria from egg
• can exclude significant portion of the population as potential contributors to the hair sample
• Cannot distinguish from individuals who are maternally related
– Anybody on mother’s side of the family

31. Testing for Drugs in the Shaft
• Human hair growths at a rate of 1.3 cm per (.44 mm per day)
• Hair grows from skin, chemicals being excreted by skin become incorporated into hair
• During testing, the hair is dissolved in an organic solvent and any substances incorporated in hair are released
• A forensic chemist can then perform various tests to determine the presence of various substances
– This analysis can provide evidence of poisoning or drug use