1. Chapter 3 The Study of Hair By the end of this chapter you will be able to:
identify the various parts of a hair
describe variations in the structure of the medulla, cortex, and cuticle
distinguish between human and nonhuman hair
determine if two examples of hair are likely to be from the same person
explain how hair can be used in a forensic investigation
calculate the medullary index for a hair
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Forensic Science: Fundamentals & Investigations, Chapter 3

2. History of Hair Analysis
Hair was recognized as trace evidence in the late 1800’s during a murder case.
Alfred Swaine Taylor and Thomas Stevenson, in 1883, wrote a forensic science text that included a chapter on hair.
Victor Balthazard and Marcelle Lambert, in 1910, published a comprehensive study of hair.
Dr. Sydney Smith, in 1934, first used a comparison microscope to analysis hairs side by side.
Advances continue today with chemical tests, neutron activation analysis, and DNA analysis.
Forensic Science: Fundamentals & Investigations, Chapter 3

3. The Function and Structure of Hair
Hair on mammals helps to regulate body temperature, decrease friction, and protect against sunlight.
Hair consists of (a) a hair shaft and a root consisting of (b) a follicle embedded in the skin (c) a papilla to supply nutrients and blood
A hair has three layers (illustrated above): the inner medulla, the cortex, and the outer cuticle.
Forensic Science: Fundamentals & Investigations, Chapter 3

4. Properties of Hair…Why Use it?
Hair is a common form of evidence in many homicide and sexual assault cases – easily left behind
Hair exhibits a range of characteristics such as color, length, and diameter
The parts that are easily seen by use of a microscope are the medulla and the cortex.
It is very difficult to see the hair cuticle however, the cuticle keeps their hair from decomposing
May be tested for chemical use and DNA analysis.
Forensic Science: Fundamentals & Investigations, Chapter 3

5. The Function and Structure of Hair
Forensic Science: Fundamentals & Investigations, Chapter 3

6. Types of Cuticle and Cortex The Outer 2 Layers
The Cuticle is the outermost layer made of over-lapping scales that protect the inner layers of the hair.
The Cortex is the thickest layer containing most of the pigment giving hair its color.
The distribution of pigment in the cortex varies from person to person.
Pigment, commonly, is denser nearer the cuticle.
Forensic Science: Fundamentals & Investigations, Chapter 3

7. Types of Medulla
The medulla (the inner section) can be hollow or filled, absent, fragmented, continuous, doubled, pigmented, or un- pigmented.
Forensic Science: Fundamentals & Investigations, Chapter 3

8. Hair Photos
Can you identify the type of medullary pattern- continuous, interrupted and fragmented?
Forensic Science: Fundamentals & Investigations, Chapter 3

9. Types of Hair Buckled Blunt Double Medulla
The cross section of a hair can be circular, triangular, irregular, or flattened influencing the curl of the hair.
The texture of a hair can be coarse or fine.
Different regions of the body on which hair can vary are (1) head, (2) eyebrows and lashes, (3) mustache and beard, (4) underarms, (5) overall body (auxiliary hair), and (6) pubic.
Forensic Science: Fundamentals & Investigations, Chapter 3

10. The Life Cycle of Hair Hair proceeds through 3 stages as it develops:
During the long anagen stage, hair actively grows. The cells around the follicle rapidly divide and deposit materials in the hair.
In the catagen stage, the hair grows and changes.
Hair is in the telogen stage when the follicle becomes dormant. During this stage, hairs easily can be lost.
Forensic Science: Fundamentals & Investigations, Chapter 3

11. Stages of Hair Development
Forensic Science: Fundamentals & Investigations, Chapter 3

12. Treated Hair
Forensic investigators sometimes can link hair from a location with an individual.
Bleaching disturbs the scales on the cuticle and removes pigment leaving hair brittle and a yellowish color.
Dyeing colors the cuticle and the cortex of the hair shaft.
Because of this and because hair grows daily, a person’s treated hairs will have specific char- acteristics in common with her or his lost hairs.
Forensic Science: Fundamentals & Investigations, Chapter 3

13. Racial Differences
Hair examiners have identified some physical characteristics that generally can be associated with broad, racial groups.
These characteristics, however, will not apply to all individuals in these groups.
In addition, at times, it will be impossible to assign specific hairs to any of these groups be-cause their characteristics are poorly defined or hard to measure.
Forensic Science: Fundamentals & Investigations, Chapter 3

14. Animal Hair and Human Hair
Core: the medulla -- Thickest layer: the cortex --
Outermost: the cuticle
Pigmentation in animal hair is denser toward the medulla. In Humans it tends to be denser toward the cuticle.
Unlike human hair, animal hair abruptly can change colors in banded patterns.
The medullary index is different. In animals the medulla is much thicker than it is in humans.
Forensic Science: Fundamentals & Investigations, Chapter 3

15. To distinguish between animal and human hair use a Medullary Index
diameter of hair’s medulla
Medullary Index =
diameter of the hair
M.I. = <.33 hair is human
M.I. =>.5 or more, hair is animal
Forensic Science: Fundamentals & Investigations, Chapter 3

16. Animal Hair and Human Hair
Spinous Coronal Imbricate
The outermost layer of the hair shaft (the cuticle), is typically different in animals and humans.
The cuticle scales in animals tend to resemble petals (spinous) or they give the appearance of a stack of crowns (coronal).
The cuticle scales in humans commonly are flattened and narrow (imbricate).
Forensic Science: Fundamentals & Investigations, Chapter 3

17. Cat hair
Forensic Science: Fundamentals & Investigations, Chapter 3

18. Dog hair
Forensic Science: Fundamentals & Investigations, Chapter 3

19. Rabbit hair
Forensic Science: Fundamentals & Investigations, Chapter 3

20. Pictures of Rat Hairs
Forensic Science: Fundamentals & Investigations, Chapter 3

21. Race and Hair
Hair cannot be absolutely identified as to race. Traits associated are often and characteristics of races are less distinct.
Forensic Science: Fundamentals & Investigations, Chapter 3

22. Additional Information
Individuals of Oriental origin usually have a continuous medulla
Dyed hair shows color distributed in cortex and medulla
Bleached hair has a yellowish tint
As hair grows, natural color returns
Forensic Science: Fundamentals & Investigations, Chapter 3

23. Normal hair
Forensic Science: Fundamentals & Investigations, Chapter 3

24. Damaged hair Burned Razor cut Split ends
Forensic Science: Fundamentals & Investigations, Chapter 3

25. Pictures of Damaged Hair
Forensic Science: Fundamentals & Investigations, Chapter 3

26. Hair is ‘class evidence’ not individual evidence What’s the difference? Varies in texture from one region of the body to another Round or oval in cross-section in Caucasians Oval or flat in cross-section in African Americans
Forensic Science: Fundamentals & Investigations, Chapter 3

27. DNA Analysis
Only possible if ‘bulb’ at the base of the hair is intact
Bulb
Forensic Science: Fundamentals & Investigations, Chapter 3

28. Forcibly removed Follicle intact Pulled
Forensic Science: Fundamentals & Investigations, Chapter 3

29. A Baseline
Up to 50 hairs from each body region (head, pubic area, facial hair, etc., are needed to provide a baseline for comparability
Forensic Science: Fundamentals & Investigations, Chapter 3

30. Using Hair in an Investigation
Macroscopic investigation can indicate length, color, and curliness.
Microscopic investigation can indicate fine detail in hair structure.
Phase contrast microscopy, for example, can show the presence of dye or other treatments.
Electron microscopes can provide more detail of the surface or interior of the sample. In the sample above, note the overlapping scales and the pigment granules in the cortex.
Forensic Science: Fundamentals & Investigations, Chapter 3

31. Conclusions that Can be Drawn from Hair
The area of the body from which the hair came
The manner in which the hair was removed, such as having been cut or forcibly pulled out.
Differentiations between hair samples based on shampoo residues
Whether the hair has been bleached or dyed
What contaminants are in the hair, such as gunshot residues, blood, semen, soil, paint, pet hair, or fibers
Whether the hair has been subject to force, such as burning.
What drugs, if any, were ingested, as well as how long ago they were taken.
Whether the person is a smoker or nonsmoker.
Forensic Science: Fundamentals & Investigations, Chapter 3

32. Testing for Substances in the Hair Shaft
Chemicals that the skin absorbs often can be detected by analysis of the hair shaft.
A forensic scientist can perform chemical tests for the presence of various substances.
The hair shaft can be examined in sections to establish a timeline for exposure to toxins.
Neutron Activation Analysis (NAA) can determine concentrations of substances in the sample.
Forensic Science: Fundamentals & Investigations, Chapter 3

33. Testing the Hair Follicle
Microscopic assessment of the follicle is performed first because it is cost effective and quick.
If a microscopic match is found, the follicle can be blood tested and perhaps show the blood type.
If a microscopic match is found, the follicle can be DNA analyzed to provide identification with a high degree of confidence.
Forensic Science: Fundamentals & Investigations, Chapter 3

34. Summary
Hair consists of a (a) hair shaft produced by a (b) follicle embedded in the skin.
The shaft consists of an outer cuticle, a cortex, and an inner medulla.
Various hair treatments produce characteristic effects useful to forensic experts.
Some characteristics allow them to be grouped into general racial categories.
Forensic experts examine hair using chemicals, light, electrons, neutrons, and DNA sequencing.
Forensic Science: Fundamentals & Investigations, Chapter 3