1. Trace Evidence
HAIRS

2. What is Locard’s Exchange Principle?
Review …
What is Locard’s Exchange Principle?

3. Edmund Locard
The Locard Exchange Principle states that whenever two objects come into contact, a mutual exchange of matter will take place between them.
VICTIM SUSPECT
PHYSICAL EVIDENCE
OBJECT CRIME SCENE

4. We lose a lot of hair!
How many would you say we lose a day?
50 – 100!!!
**In other words, there’s a good chance you would lose one at a crime scene … especially if there is a struggle!

5. What is trace evidence?
Trace evidence is any physical evidence that is extremely small; it can be man-made or naturally occurring.
Examples: hair, fibers, body fluids, paint, glass
Collection and preservation should be done in such a way that the evidence is in the same form when it goes to the lab as it was at the crime scene.
OF COURSE!!!
Collection methods include hand picking, vacuuming, and tape lifts (most common).

6. Test Questions for Trace Evidence
What is it?
What is its source?
How common is it?
Can it be identified to a single source?

7. Hair
Hair is one of the most frequently found pieces of evidence at a crime scene. It can provide a link between the criminal and the act.
Although it is circumstantial evidence, hair can give us a lot of information such as …
Where a criminal entered or exited a crime scene
Whether a suspect had contact with a victim
Whether a suspect wore an article of clothing

8. Hair
Although we cannot yet INDIVIDUALIZE a strand of hair, one can determine:
Human or animal?
Race
Origin
Manner in which the hair was removed
Treated hair
Drugs ingested

9. WHAT IS HAIR?
Hair is a slender, threadlike outgrowth of the skin that grows out of an organ called a hair follicle.

10. Hair Morphology – 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

11. Hair Follicles
Follicles are present on all skin excepts palms, soles, lips, nipples
In some areas that grow hair, the hair may be fine, while in others it may be thick
A hair grows out of a deep tube that extends from the surface of the skin, all the way into the dermal layer – this is a follicle
Each hair follicle is also connected to sebaceous glands that produce oils and other secretions

12. Hair follicle (continued) …
The follicle contains the growing hair shaft
The base of the hair is composed of actively dividing epidermal cells
These epidermal cells are nourished by dermal blood vessels near the hair base – this area at the base of the hair follicle is called the hair papilla

14. How does the hair grow?
As the epidermal cells divide, they push older cells upward through the follicle
As the older cells move away from the nutrient supply, they become keratinized and die
These dead keratinized epidermal cells are what make up a strand of hair
Hair color is genetically determined and is pigmented by melanocytes - the more the melanin in the dead epidermal cells, the darker the hair

15. Phases of Hair Growth
Anagen – can last up to 6 years. In this phase, the hair root is still attached to the hair follicle and grows. The root appears plump and “flame-shaped”
Catagen – the hair continues to grow, but at a slower rate. This slowed-down growth rate can last for 2 to 3 weeks. The root bulb shrinks and appears elongated.
Telogen – Telo means “end”. This is the phase in which the root begins to look like a club. The hair will slowly get pushed out of the follicle. This slow loss can take 2 to 6 months. ( hairs per day on average)
[Naturally shed hair has a club shaped root, forcibly removed hair shows damage and the stretching of the root.] 15

17. THE ROOT
The root and surrounding cells in the hair follicle provide the tools necessary to produce hair and continue its growth.
When pulled forcibly from the head during the anagen stage, some translucent tissue surrounding the hair’s shaft near the root may be found. This is called the “follicular tag.”
By using DNA analysis on the follicular tag, the hair may be individualized.

18. What the root can tell us …
Naturally shed hairs display undamaged club shaped roots. (below)
A forcibly removed hair will show a stretched or damaged root (top right) and may even have tissue attached (bottom right).

19. Hair Tip Clockwise from top left: Natural tip, scissor cut, split end, burned, razor cut

20. HAIR SHAFT
The shaft of the hair is the part most observed by Forensic Scientists and is composed of three layers.
Cuticle
Medulla
Cortex

21. Hair Cuticle
The cuticle is the outermost layer of hair which is covered with scales.
The cuticle provides protection.
Scales always point toward the tip of the hair.
These scales differ between species of animals and are named based on their appearance.

22. Imbricate Scales
The imbricate or flattened scales type consists of overlapping scales with narrow margins. They are commonly found in human hairs and many animal hairs. 22

23. Coronal Scales
Crown-like Scales that completely encircle the hair shaft.
They have a very fine diameter and resemble a stack of paper cups. Coronal scales are commonly found in the hairs of small rodents and bats. 23

24. Spinous Scales
Spinous or petal-like scales are triangular in shape and protrude from the hair shaft. They are found in of mink hairs and on the fur hairs of seals, cats, and some other animals. They are never found in human hairs. 24

25. DEER (120X)
HUMAN HEAD HAIR (600X)
DOG (1250X)
BAT (300X)?
CAT (2000X)
HORSE (450X)

26. The CORTEX The cortex is the main body of the hair shaft.
Its major forensic science 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 hairs of different individuals.
The cortex also contains cortical fusi, or air spaces, usually found near the root. 26

27. The Cortex
Cuticle
Pigment Granules
Cortical Fusi

28. Hair Medulla
The medulla is the hair core that is not always present. The medulla comes in many different types and patterns.
Types
Continuous
Intermittent or interrupted
Fragmented
Absent or not-present
(the presence of a medulla varies
from individual to individual and even
among hairs of a given individual.

29. Three human head hairs 29

30. Medulla Shape UNISERIAL MULTISERIAL VACUOLATED LATTICE AMORPHOUS
Medulla shape is another characteristic that varies from species to species
Medulla Shape
UNISERIAL
MULTISERIAL
VACUOLATED
LATTICE
AMORPHOUS

31. Rabbit Medulla
Rabbit medulla is different depending on the type (location on the body) of hair.
The one on the top is multiserial.
The one on the bottom is uniserial and is found in the rabbit guard hair.

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 and for animal hair it is usually greater than ½.

33. DEER (100X)
HUMAN HEAD HAIR (450X)
DOG (450X)
RABBIT (450X)
CAT (450X)
MOUSE (450X)

34. Hair as Evidence at Crime Scenes
Hair is the most common trace evidence found at a crime scene.
The most common request is to determine whether or not hair recovered from at the crime scene compares to hair removed from the suspect.
PROBLEM: Microscopic hair examinations tend to be subjective and highly dependant on the skills and integrity of the analyst.

35. Hair Comparison Color Length Diameter
Distribution, shape, and color intensity of pigment granules
Dyed hair has color in the cuticle and the cortex
Bleaching removes color and gives the hair a yellow tint.
Scale types
Presence or absence of medulla
Medullary type
Medullary pattern
Medullary index

36. Questions
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?

37. Part of the body? Based on structural analysis of the hair:
Most head hair are similar to each other in diameter and the pigment is evenly distributed throughout the shaft, unlike other body hair. They may have absent, continuous, or discontinuous medulla.
Pubic hair is short, coarse and curly and exhibit considerable diameter variation called “buckling.”

38. Part of the body (continued)
Beard/Mustache hairs are coarse and triangular in cross section. They have a wide medulla and blunt ends due to shaving.
Limb hairs (from the legs and arms) are shorter in length, arc-like in shape, and often abraded or tapered at the tips. The pigment in limb hair is generally granular in appearance, and the medulla is trace to discontinuous.

39. Parts of the body
Head hair
Pubic hair “buckling”
Beard hair

40. Racial Origins
Caucasian – is a slightly irregular oval shape in cross section. It can range from straight to curly and every degree of curl between. It has the widest range of colors; black, auburn, shades of fair and brown to a near white blond. The hair grows out of the skull at an oblique angle, at a rate of about 1.2cm a month. The pigment granules are sparse to moderately dense with fairly even distribution .

41. Racial Origins
African - thin and almost flat in cross section, with a tendency to very tight curls. Sometimes it grows in tiny clumps, called peppercorn hair. African hair grows the slowest, at about 0.9cm a month. It’s angle of growth is nearly parallel to the scalp. In color, it is nearly always black in Africans. The only time you’ll see  hair of a different color is if the individual is an albino, or has European ancestry, or if they dye it. Naturally colored African hair has densely distributed pigment granules (hair shaft may be opaque) that are arranged in prominent clumps. The hairs also twist irregularly about their longitudinal axis, it has been described as a twisted oval rod.

42. Racial Origins
Asian - grows the fastest at an average of 1.3 cm a month. Its is more circular in cross section, although not perfectly regular. It has a larger diameter and cuticle than Caucasian or African. It grows out of the scalp at a right angle. The pigment granules are larger than Caucasians and densely distributed and often arranged in large patchy areas or streaks. It is nearly always black.

43. Age of the hair’s owner
The age of an individual cannot be determined definitively by a microscopic examination; however, the microscopic appearance of certain human hairs, such as those of infants and elderly individuals, may provide a general indication of age. The hairs of infants, for example, are generally finer in microscopic appearance. As individuals age, hair can undergo pigment loss and changes in the configuration of the hair shaft to become much finer and more variable in diameter. 43

44. Sex of the hair’s owner
Although the sex of an individual is difficult to determine from microscopic examination, longer, treated hairs are more frequently encountered in female individuals. Sex can be determined from a forcibly removed hair (with tissue), but this is not routinely done. 44

45. Forcibly removed
If you pull a hair that is in anagen phase, it has a follicular tag attached to the root – this tag is very important for forensic analysis –
tells you if a hair has fallen out or pulled out – hair pulled out usually has the follicular cells
How quickly it has been pulled out – hair pulled quickly has the follicular cells attached
The follicular tag is also a useful source of DNA 45

46. Nuclear DNA from hair
The best source of nuclear DNA is the follicular tag.
If absent, nuclear DNA can be retrieved from the root, however, hair in the anagen stage will yield more DNA than hair in other phases.
So hairs found at crime scenes will not necessarily be good sources of nuclear DNA unless they were pulled out.

47. Mitochondrial DNA from hair
If nuclear DNA is not found, an examiner can locate the mitochondria of the hair cells where mtDNA is found.
mtDNA is only passed from mother to child, whereas nuclear DNA is passed by both parents.

48. Collection of Hair Evidence
Hairs are collected using tweezers and they are stored using the druggist fold and a secondary container.
Questioned hairs must be accompanied by an adequate number of control samples
From the victim
From the suspects
Others who may have deposited hair at the scene
Control Sample
50 full length hairs from different areas of the scalp
24 full length pubic hairs
Entire hair length is collected (pulled from root)