1. Hair Analysis – Part I (Chapter 11)
A Study of Trace Evidence

2. Morphology & Structure of Hair

3. Hair Morphology

6. Morphology: Cuticle
Protective coating made of overlapping scales, produce a characteristic pattern
Scales always point toward tip of hair
Not useful in individualizing human hair
Can be used for species identification

7. Morphology: Cuticle

8. Cuticle Types
Mosaic
Pectinate
Diamond
Imbricate
Petal

9. Morphology: Cortex
Made of spindle-shaped cells aligned in a regular array, parallel to the length of the hair
Embedded with pigment granules that give hair its color
The color, shape and distribution of the granules provide points for forensic comparison

10. Morphology: Medulla
Canal like structure of cells that runs through the center of the cortex

11. Medulla Medulla vary between individuals
Vary between hairs of the same individual
Some hairs have no medulla

12. Medullary Index
Measure of the diameter of the medulla relative to the diameter of the hair shaft
Usually expressed as a fraction
Humans: medullary index < 1/3
Animals: medullary index > 1/2

13. Medulla of Different Species

14. Animals
RABBIT
MUSKRAT
COW

15. Medulla of Different Species

16. Medulla Related to Hair Color
Very fair
Light Brown
Brown-Black
Red

17. Forensic Analysis of Medulla
Presence of medulla varies quite a bit: even hair to hair
Human head hairs generally have no medulla or may be fragmented ones; except Mongoloid race whose medulla is usually continuous
Most animals have medulla that is continuous or interrupted
The shape of the medulla can help identify a species
Examples:
Most animals and humans: cylindrical
Cats: pearl shape
Deer: spherical occupying whole hair shaft

18. Variation in Hair by Sex
Stained sex chromatin in the nuclei of human cells showing the female-indicative Barr body (bright spot, top) and the male-indicative Y body (bright spot, bottom)

19. Racial Determination
Negroid
Mongoloid
Caucasian

20. Hair Roots
Pulled Forcibly Removed Shed

21. Tip of the Shaft
Burned Cut Razored Split

22. Morphology: Root
Human hair grows in three developmental stages: anagen, catagen, and telogen phases

23. Phases 1) Anagen - Growth Phase 2) Catagen - Transitional phase
3) Telogen - Resting Phase

24. Root: Anagen Phase
Initial growth phase during which hair follicle is actively producing hair, phase may last 6 years, root is flame like in appearance
When pulled this root may contain a follicular tag (rich source of DNA)
Root w/ follicular tag

25. Root: Catagen Phase
A transition phase—hair grows at a decreasing rate for two to three weeks—elongated appearance as root bulb shrinks and is being pushed out of hair follicle

26. Root: Telogen phase
Hair growth has ended—root takes on a club-like appearance—during two-six month period, the hair will be pushed out of the follicle causing the hair to shed naturally

27. Identification and Comparison
Establish if the hair is human or animal
Compare if the hair retrieved at the crime scene is compatible from a known hair of a particular individual
The ability to distinguish human from animal is easy when compared to that of human hair comparison
Various morphological characteristics between individuals and the same individual

28. Identification and Comparison
Microscopic examination
Animal or human
Species of animal
Important characteristics:
Scale structure
Medullary index
Medullary shape

29. Identification and Comparison
Scalp hair
Pubic hair
Comparison microscope
Hair from any part of the body exhibits a wide range of characteristics the examiner must have an adequate number of known hair samples that are representative of all its features

30. Identification and Comparison
Compare
Length
Color
Diameter
Presence or absence of medulla
Distribution, shape and color intensity of the pigment granules present in the cortex
Dyed, bleached or natural hair

31. Identification and Comparison
Dyed hair: dye color found in cuticle as well as throughout cortex
Bleaching: removes pigment from the hair and gives a yellowish tint
If there has been growth of hair since last bleach or dye treatment: natural-end is distinct in color
Hair is known to grow at an approximate rate of 1 cm/month
Therefore can estimate the time since last appointment or treatment

32. Identification and Comparison
Morphological abnormalities;
Diseases
Deficiencies
Fungal and nit infections
If one human head hair taken from the crime scene is found to be similar to a representative hair from a suspect’s head, the odds against it from originating from another person are about 4500 to 1
The odds of two different pubic hairs originating from two different individuals is 800 to 1

33. What can be determined Body areas:
Scalp hairs show little variation of diameter and have more uniform distribution of pigment color
Pubic hair are short, curly with a wide range of variations in shaft diameter and a continuous medulla
Beard hairs: coarse and usually triangular in cross-section with blunt tips from cutting or shaving

34. What can be determined Racial origin:
Can distinguish between Negroid and Caucasian head hair
Negroid hair: normally kinky, containing dense, unevenly distributed pigments, flat to oval in shape
Caucasian hair: straight or wavy, with very fine to coarse pigments that are more evenly distributed when compared to Negroid hair
Cross sections of Caucasian hair are oval to round in shape
These are very general in nature

35. What can be determined
Age cannot be determined from morphology with any degree of certainty except with infant hair
Fine, short in length, have fine pigment and are rudimentary in character
Sexual discrimination at this time is not considered to be a routine forensic technique, but can be made with root tip DNA
Microscopic examination of the hair root may establish if the hair has fallen out or has been pulled out
Hair root with follicular tissue adhering to it is indicative that the hair has been pulled out

36. What can be determined
The current approach for examination of hair is the morphological characteristics
Breakthroughs in nuclear DNA typing has extended the technology to the individualization of human hair
Examiners can link a particular human hair to an individual by characterizing the nuclear DNA in the hair root or follicular tissue adhering to the root
Higher rate of success extracting DNA from a hair in the anagen phase or anagen hairs entering the catagen phase then those in the telogen phase

37. Collection
Crime scene hairs must always be accompanied by an adequate amount of control samples from the victim and from suspects
Hair from any one area of the body varies significantly. The questioned hairs and control hairs must come from the same area of the body

38. Collection of Hair Specimen

39. Collection
Forensic hair comparisons usually involve scalp or pubic hairs
Collection of 50 full length hairs from all areas of the scalp
A minimum of two dozen full length pubic hairs
In rape cases care must be taken to first comb the pubic area to remove all foreign hair present before the victim is sampled for control hair