1. HAIR ANALYSIS

2. Introduction
Hair is encountered as physical evidence in a wide variety of crimes.
Although it is not yet possible to individualize a human hair to any single head or body through its morphology, it still has 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.

3. Significance of Hair Evidence
Hairs can be transferred during physical contact, their presence can associate a suspect to a victim or a suspect/victim to a crime scene.
The types of hair recovered and the condition and number of hairs found all impact on their value as evidence in a criminal investigation.
Comparison of the microscopic characteristics of questioned hairs to known hair samples helps determine whether a transfer may have occurred

4. Basics of Hair Evidence
Hairs are composed primarily of the protein keratin, can be defined as slender outgrowths of the skin of mammals.
Each species of animal possesses hair with characteristic length, color, shape, root appearance, and internal microscopic features that distinguish one animal from another.
Considerable variability also exists in the types of hairs that are found on the body of an animal.
In humans, hairs found on the head, pubic region, arms, legs, and other body areas have characteristics that can determine their origin. On animals, hair types include coarse outer hairs or guard hairs, the finer fur hairs, tactile hairs such as whiskers, and other hairs that originate from the tail and mane of an animal.

5. Morphology of Hair
Hair is an appendage of the skin that grows out of an organ known as the hair follicle.
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 Diagram

7. Cuticle and Cortex
The cuticle is the scale structure covering the exterior of the hair.
The scales always point towards the tip of the hair.
The scale pattern is useful in species identification.
The cortex is the main body of the hair shaft.
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.

8. Medulla
The medulla is a cellular column running through the center of the hair.
The medullary index measures the diameter of the medulla relative to the diameter of the hair shaft.
For humans, the medulla generally occupies less than one-third the diameter of the shaft, while for animals it is generally one-half or greater.
The medulla may be continuous, interrupted, fragmented, or absent.
The presence of the medulla varies from individual to individual and even among hairs of a given individual.
Medullae also have different shapes, depending the species.

9. Medulla Patterns

10. Hair Diagram

11. 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.

12. Hair and Types of Loss
Naturally shed hairs, such as a head hair dislodged through combing will display undamaged, club-shaped roots.

13. Hair and Types of Loss
A hair forcibly removed from the scalp will exhibit stretching and damage to the root area.
Forcibly removed hairs may have tissue attached.

14. Hair Anatomy & Growth
Hairs undergo a cyclical growth (anagen) and resting phase (telogen)
Anagen phase - the hair is actively growing, and materials are deposited in the hair shaft by cells found in the follicle. Dividing cells form the major components of the hair—the medulla, cortex, cuticle, and accompanying root sheath
Telogen phase - the follicle is dormant or resting. Hairs are routinely lost during the telogen phase

15. Animal Hairs
Human Cat Dog Mouse

16. Animal Hairs
Animal hairs do not possess enough individual microscopic characteristics to be associated with a particular animal to the exclusion of other similar animals
If the questioned hair exhibits the same microscopic characteristics as the known hairs, it is concluded that the hair is consistent with originating from that animal

17. Human Hairs Physical contact may result in the transfer of hairs
Primary transfer— transfer directly from the region of the body where they are growing
Secondary transfer—transfer from the clothing of individuals.
Approx. 100 head hairs are shed by an individual each day.
Contact between a victim and a suspect's environment can easily cause a secondary transfer of hair. Hairs that are found on the clothing of suspects or victims and appear to have fallen out naturally may be the result of primary or secondary transfer. Hairs that have been forcibly removed may suggest a violent confrontation

18. Head Hair Usually the longest hairs on the human body
Characterized as having a uniform diameter and, often, a cut tip
Alterations to the natural appearance of hair include use of hair dyes, rinses, permanents, frosts, and other chemical applications. Environmental alterations can result from exposure to excessive sunlight, wind, dryness, and other conditions
It is recommended that head hair samples be obtained as soon as possible from suspects and victims of crime. Head hair samples obtained years after a crime are generally not suitable for meaningful comparison purposes

19. Glass-Cut or Broken Hair Tip
Cut Hair Tip
Worn Razor-Cut Tip

20. Pubic Hairs
Considerable variation exists between individuals in the population
Pubic hairs are not subject to as much change as head hairs over time, and because of this, a sample taken a year or more after a crime may still be suitable for meaningful comparison purposes
Generally coarse and wiry in appearance. They exhibit considerable diameter variation
Tapered tips are common, these hairs may also be cut.

21. Facial Hairs Commonly called beard hairs or mustache hairs
These hairs are coarse in appearance and can have a triangular cross section
Characteristics include a wide medulla and a razor- cut tip.
The presence of facial hairs on the clothing of a suspect or victim may help establish contact between these individuals. While these hairs may be compared microscopically, the significance of the association may not be as great as head hair and pubic hair associations.

22. Limb Hairs Hairs from the legs and arms constitute limb hairs
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.
While limb hairs are not routinely compared in a forensic laboratory, they can differ in appearance between individuals.
Differences are not considered sufficient to allow limb hairs to be of value for meaningful comparison purposes.

23. Types of Human Hair by Race
Caucasian Negroid Mongolid

24. Negroid (African)
Hairs of Negroid or African origin are regularly curly or kinky, have a flattened cross section, and can appear curly, wavy, or coiled.
Negroid pigment granules are larger than those found in Mongoloid and Caucasian hair and are grouped in clumps of different sizes and shapes.

25. Caucasoid (European)
Hairs of Caucasoid or Caucasian origin can be of fine to medium coarseness, are generally straight or wavy in appearance, and exhibit colors ranging from blonde to brown to black.
The hair shafts of Caucasian hairs vary from round to oval in cross section and have fine to medium-sized, evenly distributed pigment granules.

26. Mongoloid (Asian)
Hairs of Mongoloid or Asian origin are regularly coarse, straight, and circular in cross section, with a wider diameter than the hairs of the other racial groups.
The outer layer of the hair, the cuticle, is usually significantly thicker than the cuticle of Negroid and Caucasian hairs, and the medulla, or central canal, is continuous and wide.

27. Human Hairs to Determine Age
The age of an individual cannot be determined definitively by a microscopic examination
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 are generally finer and less distinctive 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.

28. Hair Microscopy
Examination of human hairs in the forensic laboratory is typically conducted through the use of light microscopy
Two-step process—the identification of questioned hairs and the comparison of questioned and known hairs using a comparison microscope

29. Comparing Strands The comparison microscope is an indispensable tool
When comparing strands of human hair, the criminalist is particularly interested in matching the color, length, and diameter.
A careful microscopic examination of hair will reveal morphological features that can distinguish human hair from the hair of animals.
Scale structure, medullary index, and medullary shape are particularly important in animal hair identification.

30. Comparing Strands
Other important features for comparing human hair are:
the presence or absence of a medulla
the distribution, shape, and color intensity of the pigment granules present in the cortex
The most common request is to determine whether or not hair recovered at the crime scene compares to hair removed from the suspect.
Microscopic hair examinations tend to be subjective and highly dependent on the skills and integrity of the analyst.

31. Checking for Understanding…
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?

32. Hair and DNA
Recent major breakthroughs in DNA profiling have extended this technology to the individualization of human hair.
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 telogen (final) phase.
Often, when hair is forcibly removed a follicular tag, a translucent piece of tissue surrounding the hair’s shaft near the root may be present.
This has proven to be a rich source of nuclear DNA associated with hair.

33. Hair and Mitochondrial DNA
Mitochondrial DNA can be extracted from the hair shaft.
Mitochondrial DNA is found in cellular material located outside of the nucleus and it is transmitted only from the mother to child.
Why might comparing mitochondrial DNA be used for?

34. Collection and Preservation
As a general rule, forensic hair comparisons involve either head hair or pubic hair.
The collection of 50 full-length hairs from all areas of the scalp will normally ensure a representative sampling of head hair.
A minimum collection of two dozen full-length pubic hairs should cover the range of characteristics present in pubic hair.
Hair samples are also collected from the victims of suspicious deaths during an autopsy.

35. What is this?