1. Trace Evidence : Hairs and Fibers
Chapter 10
Trace Evidence : Hairs and Fibers

2. Trace Evidence
A category of physical evidence which includes any small pieces of material, man-made or naturally occurring
Most common examples:
Hair
Fiber

3. Forensic Use of Hair
Although it is not yet possible to individualize a human hair to any single head or body through its morphology, it still has great 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. Forensic Use of Hair cont….
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 act.
From hair one can determine:
Human or animal
Race
Origin
Manner in which hair was removed
Treated hair
Drugs ingested

5. Morphology of Hair
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.

6. Hair Morphology Morphology is the Study of Structure and Form
Parts of the hair:
Shaft--part of the hair that sticks out of the skin
Root--lies below the epidermis
Follicle--structure from which the hair grows

7. Follicle

8. The Three Layers of Hair
Cuticle – outermost layer
Medulla – canal running through the hair core
Cortex – middle layer which contains color pigments

9. Hair Growth Terminology
Anagen
hair that is growing
Up to 6 yrs
Catagen
hair at rest
2-3 weeks
Telogen
hair that is dying
2-6 months
Length mm per day or 1 centimeter per month; approximately one half inch per month
Anywhere from telogen hairs are normally shed each day.

10. Cuticle (outermost layer)
The cuticle is the scale structure covering the exterior of the hair.
Scales form from overlapping hardened (keratinized) cells
The scales always point towards the tip of the hair.
The scale pattern is useful in species identification.

11. Human Cuticle Scales In order to visualize the scales
paint fingernail polish on a slide
place a hair on the polish
lift off the hair and
observe the scale imprints

12. 3 Main Cuticle Patterns Coronal Spinous Imbricate
Each of these patterns has several subcategories of patterns.

13. The 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
Rarely in human hairs.

14. Coronal
Dog
Rabbit

15. Coronal
Rat

16. 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.

17. Spinous
Cat
Mink

18. The IMBRICATE or flattened-scale type
Consists of overlapping scales with narrow margins
They are commonly found in human hairs and many animal hairs

19. Imbricate – Human

20. Hair Cortex (middle layer)
The cortex is the main body of the hair shaft.
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
Ovoid bodies larger round or oval shaped solid structures present in some species.

22. Pigment Granules & Ovoid Bodies

23. Cortex
Its major forensic importance is the fact that it is embedded with the pigment granules that impart hair with color.
The color, shape, and distribution of these granules provide the criminalist with important points of comparison among the hairs of different individuals.

24. Medulla (innermost layer)
The medulla is a central canal running through the center of the hair.
The presence of the medulla vary from individual to individual and even among hairs of a given individual.
Medullae also have different shapes, depending the species.

25. Medulla
The medulla is the hair core that is not always present. The medulla comes in different types and patterns.
Types:
Continuous
Intermittent or interrupted
Fragmented
Absent--not present

26. Hair Medulla Patterns Uniserial Multiserial Vacuolated Lattice
Amorphous (without a distinct pattern)

27. Cat – uniserial - continuous

28. Rabbit – multi-serial – continuous

29. Dog – vacuolated/amorphous -continuous

30. Rat – multiserial – continuous

31. Human – amorphous if present
Human head hairs generally have no medulla or have fragmented ones.
Rarely do they show a continuous pattern.
An important exception is in the Asian races, whose head hairs usually have continuous medullas.

32. 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.

33. Root
The root and other surrounding cells in the hair follicle provide the tools necessary to produce hair and continue its growth.
When pulled from the head, some translucent tissue surrounding the hair’s shaft near the root may be found. This is called a follicular tag.
By using DNA analysis on the follicular tag, the hair may be individualized.

34. If a hair is forcibly removed…
During the anagen phase, the root is bulb shaped and attached to the follicle. A hair would have to be forcibly removed during this phase. Therefore, the root will show signs of trauma. This is a very important clue in violent crimes.

35. Telogen Hair Root
Naturally shed hairs display club shaped root. The root does not have any signs of trauma.

36. Human hair roots are different from animal hair roots.

37. Cat Hair Root

38. Squirrel Whisker Root

39. DNA Evidence from Hair
The hair shaft contains abundant mitochondrial DNA--inherited only from our mothers. It can be typed by comparing relatives if no DNA from the body is available.
Only the root contains nuclear DNA
The probability of detecting DNA in hair roots is more likely for hair being examined in its anagen or early growth phase as opposed to its catagen (middle) or telogen (final) phases.

40. Summary of Human vs. Animal
In order to determine if a hair is human or animal:
1. Compare the hair scales
2. Compare the medullary index
3. Compare the medullary shape/pattern
4. Compare the hair root

41. If the hair is human…
Once the determination is made that the hair is human then race, origin and hair treatments can be decided.

42. Usually curly, containing dense, unevenly distributed pigments.
Mongoloid
Usually curly, containing dense, unevenly distributed pigments.
Cross section is flat to oval in shape.
Cross section varieties.
Usually straight, and coarse. Contains pigment granules larger in size than Caucasians.
Cross section is round in shape.
Negroid
Usually straight or wavy with very fine to coarse pigments that are more evenly distributed .
Cross section is oval to round in shape.
Caucasoid

43. Race Identification Negroid Blacks 60-90 µm Flat Dense & Clumped
Includes
Diameter
Cross Section
Pigmentation
Negroid
Blacks
60-90 µm
Flat
Dense & Clumped
Caucasoid
White Am.
European,
Mexican, & Middle Eastern µm
Oval
Evenly distributed
Mongoloid
Orientals,
&
Am. Indian µm
Round
Dense

44. Facial Hair Human head hairs range in shape from round to flat.
Beard hairs are often triangular in cross section.

45. Basics of Hair Comparisons
The comparison microscope is an indispensable tool for comparing the morphological characteristics of hair.

46. Basics of Hair Comparisons cont…
Color, Length, & diameter
Distribution, shape and color intensity of pigments granules
Dyed hair has color in cuticle and cortex
Bleaching removes pigment and gives yellow tint
Scale types
Presence or absence of medulla
Medullary type
Medullary pattern
Medullary index

47. Reliability of Hair Analysis
Hair is class evidence
Microscopic hair examinations tend to be subjective and highly dependant on the skills and integrity of the analyst.
As a rule, all positive microscopical hair comparisons must be confirmed by DNA analysis.

48. Origin of Human Hair
Scalp hair shows little diameter variation and more uniform distribution of pigment color.
Beard hair is coarse and has
blunt tips.
Pubic hair is short and curly, with wide variation in shaft diameter, or buckling, and has a continuous medulla.

49. Colored Hair
Dyed hair – presence of “color” in cuticle and throughout cortex
Bleaching – removes natural pigment and gives yellowish tint
Dyed and bleached hair can be determined through microscopic examination.

50. Ingested Drugs
5-10 days after the drug is ingested, it will be present in the hair.
The drug becomes a part of the hair may be detected up to 2 years.
It takes at least 50 scalp hairs for an accurate test.

51. Other Types of Identification
Age - only infant’s hair can be determined because it is so fine.
Sex- sex cannot be determined from hair.
Manner- can determine if hair was forcibly removed. The follicle tag will still be attached.
Individualization- through positive microscopic comparison and mitochondrial DNA analysis a link from questioned hair to standard hair can be proven.

52. Collection of Hair Evidence
Questioned hairs given to the lab for analysis must be accompanied by an adequate number of control samples.
from victim
possible suspects
others who may have deposited hair at the scene
The Control Sample should include:
50 full-length hairs from all areas of scalp
24 full-length pubic hairs
The full hair is needed so the control samples will be pulled out or cut as close as possible to the skin.

53. Bill Cosby’s son
Ennis Cosby was stranded on the side of a highway due to a flat tire. As Ennis waited for help, Mikail Markhasev robbed and murdered him.
The police found the murder weapon wrapped in a blue cap. Hair was also recovered from the cap. Markhasev was convicted on the murder based on the hair evidence. He later confessed to the crime.

54. Normal hair

55. The following slides are just for Observation:

56. Damaged hair
Burned
Split ends
Razor cut