Chapter 13: Hairs
Trace evidence involves minute quantities of items you might find on places such as the body, under the
fingernails, in clothing, or at the crime scene. As suggested by Locard's Exchange Principal, the
evidence may be found on the victim or on the perpetrator. These items can include, but are not limited
to, hair, fibers, gunshot residue, paint chips, glass, impressions, volatile chemical residue etc...
Because trace evidence can be so varied, we will only focus on hair and fibers in this chapter. Other
forms of trace evidence will be studied in later chapters.
Hair & Fiber Terminology
The terms in this section are defined by how they are used in forensic hair examinations.
 Amorphous medulla is a medulla that has no distinct form, pattern, or shape when viewed with a transmitted
light microscope.
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Anagen is the active growth phase of a hair follicle in the hair growth cycle. The root from a pulled anagen
hair is elongated, may be covered with a root sheath, and is usually fully pigmented.
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Buckling is an abrupt change in the shape and orientation of a hair shaft with or without a slight twist, often
seen in pubic hairs.
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Catagen is the transitional phase of the hair follicle from the active growth phase (anagen) to the resting
growth phase (telogen) in the hair growth cycle.
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Continuous medulla is a medullary appearance showing no disruptions along the shaft of the hair.
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Cortex is the primary anatomical region of a hair between the cuticle region and the medullary region
composed of elongated and fusiform cells.
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Cortical fusi are small spaces that appear as tiny dark structures in the hair shaft; they can be filled with air
or liquid.
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Cortical texture is the relief or definition of the margins of the cortical cells when viewed using transmitted
light microscopy.
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Cross-sectional shape is the shape of a hair shaft cut and viewed at a right angle to its longitudinal axis.
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Discontinuous medulla is a medullary appearance in which the proportion of the visible areas of medulla is
greater than the areas when the medulla is not visible.
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Distal end is the end of the hair away from the root.
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Fusiform is a term that refers to a spindle-shaped (tapered at each end) gap present in the hair shaft.
Convolution is a rotation or twisting of the hair shaft that can occur naturally, from disease, or as a result of
mechanical force.
Cuticle is the outermost region of a hair composed of layers of overlapping scales.
Cuticle thickness is the relative size of the cuticle from its outer margin to the cortex when viewed
microscopically. This is usually described as thin, medium, or thick.
Eumelanin is the brown pigment occurring in human and animal hair.
Follicle is the cavity in the skin from which hair grows.
Follicular tag is tissue from a hair follicle that is still attached to the root end of a hair.
Fragmented medulla is a medullary appearance in which the proportion of the visible areas of medulla is
less than the areas when the medulla is not visible.
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Imbricate is a term that describes a scale pattern with edges overlapping in a wavy pattern. This pattern is
typical of human hair.
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Inner cuticle margin is the apparent border between the cortex and the visible cuticle.
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Known sample is a collected hair sample intended to be representative of a particular body area of a specific
person or animal.
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Lanugo are fine hairs found on newborns, lost shortly after birth.
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Looped cuticle is a feature in which the distal edges of the cuticular scales are curved from or cup toward
the hair shaft.
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Medial region is the portion of the hair between the proximal and distal ends.
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Melanin is a natural pigment of which two forms, eumelanin and phaeomelanin, determine the color of human
and animal hair.

Mongoloid is an anthropological term designating one of the major groups of human beings originating from
Asia, excluding the Indian subcontinent and including Native American Indians.

Opaque medulla is a medulla with large pockets of air causing it to appear black when viewed with
transmitted light microscopy.
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Ovoid bodies are oval-shaped, heavily pigmented bodies usually found in the hair cortex.
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Phaeomelanin is a reddish-brown to yellow pigment occurring in human and animal hair.
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Pigment distribution is the pattern of the pigment granules observed in the hair shaft, such as uniform,
peripheral, one-sided, variable, or central.
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Pigment granules are small particles in a hair that impart color. .
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Root is the follicular structure at the proximal end of a hair.
Keratin is a class of sulfur-containing fibrous proteins that forms the foundation of outgrowth tissue from the
epidermis, such as hair, nails, feathers, and horns of animals.
Lice are parasitic insects that may be found on humans. These include head lice, body or clothing lice, and
crab lice that live in the pubic region, eyelashes, or eyebrows.
Medulla is the core of the hair shaft that is composed of air vacuoles and cells.
Medullary configuration is the form of medullary cells from the proximal end to the distal end of the hair
shaft.
Peripheral region is the portion of the hair including the cuticle and the outer areas of the cortex most distant
from the medullary or central region.
Pigment aggregation is the cluster of individual pigment granules.
Pigment density is the relative abundance of pigment granules in the hair cortex when viewed
microscopically.
Proximal end is the portion of the hair towards the root.
Questioned sample is a sample of unknown origin.
Range is the variation of a specific characteristic exhibited by a hair or hairs from one person.
Representative sample is a collection of hairs from a specific body area that reflects the range of
characteristics in a person's hair.
Root sheath is the follicular tissue occasionally found surrounding a root structure.
Scales are tiny plate-like structures composed of keratin that forms the cuticle.
Serrated cuticle is a cuticle in which the outer margin has the notched appearance of a saw blade.
Shaft is the portion of the hair external to the hair follicle.
Shaft form is the macroscopic shape of the hair.
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Shaft thickness is the diameter of the hair. This may be expressed numerically or in relative terms, such a
thin, medium, or thick.
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Telogen is the last phase of the hair growth cycle when the hair root becomes keratinized and bulbousshaped (club-like).
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Texture is the appearance and feel of a hair due to its length, thickness, and shaft form.
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Trichology is the study of hair.
Tip is the most distal end of a hair shaft.
Translucent is a condition when light is transmitted through a material and diffused so that objects beyond
cannot be seen clearly. The appearance of a medulla that has cells filled with fluid rather than air is
translucent rather than opaque.
Vellus are fine body hair.
Hair1
Hairs, which 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.
Because 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.
Hair Microscopy
The examination of human hairs in the forensic laboratory is typically conducted through the use of
light microscopy. This examination routinely involves a two-step process—the identification of
questioned hairs and the comparison of questioned and known hairs. The purpose for conducting
this examination is to ascertain whether two or more individuals could have come into contact or
whether one or more individuals could have come into contact with an object. This associative
1
Heather Brannon, MD. The Biology of Hair: Structure and Function of Hair Follicles, About.com, “Dermatology,”
http://dermatology.about.com/cs/hairanatomy/a/hairbiology.htm, (accessed September 15, 2011).
evidence is particularly useful in crimes of violence, such as homicide, sexual assault, and
aggravated assault, where physical contact may have occurred. Crimes such as burglary and armed
robbery typically involve the recovery of debris and articles of clothing which may contain hairs useful
for the identification of suspects.
The value of hair evidence is related to the variability of hair characteristics between individuals in
the population, which can be visualized through the use of comparison microscopy. There are many
factors that impact on the reliability of a hair association, including experience, training, suitability of
known hair standards, and adequacy of equipment. Although hair evidence is a valuable tool in
human identification, it is difficult to establish a statistical probability for a particular association due in
part to the lack of reliable quantitative assessments of the microscopic characteristics present in
hairs.
The comparison microscope consists of two compound light microscopes connected by an optical
bridge that allows for the simultaneous viewing of questioned hairs and known hairs. Typically, a
glass microscope slide containing known or reference hairs is positioned on the stage of one
microscope, and a glass microscope slide containing a questioned hair or hairs is positioned on the
stage of the other microscope. This enables the hair examiner to compare the microscopic
characteristics of the known and questioned hairs in one field. The range of magnification used is
approximately 40X to 400X.
Fig. 7-1. Two hair samples viewed side by side
can be analyzed and compared. These two strands
were determined to be from the same individual.
The hair examination process involves many different steps, the first of which is to determine
whether the hair in question originated from an animal or a human being. If the hair originated from
an animal, it is possible to further identify it to a particular type of animal. Although certain hairs can
be attributed to species, it is not possible to identify hairs to a specific animal to the exclusion of other
similar animals. An example of this occurs when dog hairs can be associated to a particular breed
but cannot be identified to a specific dog within that breed.
Figures 7-2: Human hairs photographed under the
microscope.
Non-Human Hairs
Figures 7-3: Horse Hairs.
Figure 7-4: Dog hair.
Figure 7-5: Cat hairs.
Figures 7-6: Mouse hairs.
Figures 7-8: Rabbit hairs
Figure 7-9: Deer hair
Figures 7-10: Cow hairs
Hair Anatomy and Growth
Follicle - The follicle is a stocking-like
structure that contains several layers
with different jobs. At the base of the
follicle is a projection formed like
sticking a finger in the bottom of a
stocking and pushing it in a small
amount. This projection is called a
papilla and it contains capillaries, or
tiny blood vessels, that feed the cells.
The living part of the hair is bottom part
of the stocking surrounding the papilla
called the bulb. This bottom part is the
only part fed by the capillaries. The
cells in the bulb divide every 23 to 72
hours, faster than any other cells in the
body.
The follicle is surrounded by two
sheaths - an inner and outer sheath.
These sheaths protect and mold the
growing hair shaft. The inner sheath follows the hair shaft and ends below the opening of a sebaceous
(oil) gland, and sometimes an apocrine (scent) gland. The outer sheath continues all the way up to the
gland. A muscle called an erector pili muscle attaches below the gland to a fibrous layer around the
outer sheath. When this muscle contracts, it causes the hair to stand up.
The sebaceous gland is important because it produces sebum which is a natural conditioner. More
sebum is produced after puberty. The sebum production decreases in women throughout their lives.
The production also decreases in men, but not as much as in
women.
Shaft - The hair shaft is made up of dead, hard protein called
keratin in three layers. The inner layer is called the medulla and
may not be present. The next layer is the cortex and the outer
layer is the cuticle. The cortex makes up the majority of the hair
shaft. The cuticle is formed by tightly packed scales in an
overlapping structure similar to roof shingles (See figure 7-11 for
cuticle patterns of various animals). Most hair conditioning
products attempt to affect the cuticle. There are pigment cells that
are distributed throughout the cortex and medulla giving the hair
it's characteristic color.
Hair is present on many different regions of the body. Each region,
such as the head, pubic area, chest, axillae, and limbs, has hairs
with microscopical characteristics attributable to that region.
Although it is possible to identify a hair as originating from a
particular body area, the regions of the body that are primarily used in forensic comparisons are the
head and pubic areas. As hairs undergo a cyclical growth (anagen) and resting phase (telogen), the
visible microscopic characteristics are sufficient to determine the phase of growth of the hair.
During the anagen phase, the hair is actively growing, and materials are deposited in the hair shaft by
cells found in the follicle. Metabolically active and dividing cells above and around the dermal papilla of
the follicle grow upward during this phase, to form the major components of the hair—the medulla,
cortex, cuticle, and accompanying root sheath. In the telogen phase, the follicle is dormant or resting.
The transition period between the anagen and telogen phases is referred to as the catagen phase.
Hairs are routinely lost during the telogen phase and often become a primary source of evidentiary
material. An example of this natural shedding process can be seen when one combs through the hairs
on the head. It is not uncommon for hairs of this type to be transferred to another individual or to an
object during physical contact. Hairs can also become dislodged from the body while they are in an
actively growing state, such as by pulling or by striking with an object. The microscopical appearance of
the root area will allow for the determination of the growth phase.
On a healthy head, 80 to 90 percent of the hair follicles are in the anagen phase, 2 percent are in the
catagen phase, and 10 to 18 percent are in the telogen phase. Once the hair reaches the telogen
phase, the follicles have achieved a mature, stable stage of quiescence. During the telogen phase, the
hair is anchored in the follicle only by the root, which is club-shaped. The germ cells below the clubshaped root will give rise to the next generation of an anagen hair. The replacement of human scalp
hair occurs in a scattered mosaic fashion with no apparent wave-like or seasonal pattern. The average
period of growth for scalp hair is approximately 1,000 days; the resting phase lasts about 100 days.
Approximately 10 percent of the hairs on a human head (100/1000), therefore, are in the quiescent
telogen phase, and a minimal amount of force—such as that from combing—is required to dislodge the
hairs from the dormant follicle.
Figure 7-11: Scale or cuticle
patterns of several different kinds of
hair. (a) Human head hair (600x),
(b) dog fur (1250x), (c) Deer hair
(120x), (d) Rabbit fur (300x), (e) Cat
fur (2000x),
(f) Horse hair (450x). Reproduced
from Saferstein, Criminalistics, 5th
Ed., Prentice Hall, 1995.
Medulla Patterns:
The medulla patterns of animals may be broad,
occupying more than half of the shaft diameter.
Human head hair medulla patterns may be
classified as absent, fragmental, interrupted, or
continuous. (See Figure 7-12).
Figure 7-12 (left). Human head hair medulla parrtens.
Reference: Bisbing, Richard E., in Saferstein, Editor,
Forensic Science Handbook, Vol. 1, 2nd
Ed., Prentice Hall, 2002.
Figure 7-13 (right). Medulla patterns from different types
of hair. (a) Human head hair (450x), (b) dog fur (450x), (c)
Deer hair (100x), (d) Rabbit fur (450x), (e) Cat fur (450x),
(f) Mouse hair (450x). Reproduced from Saferstein,
Criminalistics, 5th Ed., Prentice Hall, 1995
Hair identification consists of determining the species, racial origin, and body or somatic location.
Species origin can readily be distinguished from the cuticle and medulla characteristics. (See
Figures 7-11 and 7-13.)
Three racial groups are used in forensic investigations: Caucasoid, Mongoloid, and Negroid. (See
Table 7-1)
Race
Includes
Diameter
Cross
Section
Pigmentation Cuticle
Undulation
Negroid
Blacks
60-90 μm
Flat
Dense and
clumped
─
Prevalent
Caucasoid
American,
European,
Mexican,
and
Middle
Eastern
70-100 μm
Oval
Evenly
distributed
Medium
Uncommon
Mongoloid
Orientals
and
American
Indian
90-120 μm
Round
Dense auburn
Thick
Never
Table 7-1. Racial characteristics of hair. Reference: Bisbing, Richard E., in Saferstein, Editor, Forensic Science Handbook,
Vol. 1, 2nd Ed., Prentice Hall, 2002.
Before a comparison of hair can be made, it must be determined which portion of the body the hair
originated from. (See Table 7-2).
Scalp
Pubic
Vulvar
Chest
Head hair; 100-1000 mm long, 25-125 μm diameter; 0.4 mm/day growth; small root;
tapered tip, little diameter variation; various medullation; often with cut tips; may be
artificially treated.
Pudential; 10-60 mm long; coarse diameter and prominent diameter variation and
buckling; broad medulla; follicular tags common; asymmetrical cross section twisted
and constricted; may be straight, curved, or spirally tufted.
Secondary public hair; finer and shorter than pubic hair; may be abraded.
Pectoral; moderate to considerable diameter variation; long fine archlike tip; usually
longer than public hair.
Beard
Facial hair, very coarse; 50-300 mm long; large root irregular structure; often triangular
cross section; complex medullation; blunted or razor-cut tip; grows 0.40 mm/day.
Axillary
Arm pit; 10-50 mm long; grows 0.30 mm/day; coarse, blunt tip, abraded or frayed;
usually straighter than pubic hair; many cortical fusi; sometimes yellowed and
bleached.
Eyebrow
Superciliary; 1 cm long; 0.16 mm/day growth; curved; relatively coarse for length;
smooth curve with punctuate tip and large medulla
Eyelash
Limb
Ear
Buttocks
Nose
Ciliary; less than 1 cm long; short curved pointed hair.
Leg and arm hair; 3-6 mm long; fine tip irregularly medullated; often indistinctly and
slightly pigmented.
Tragi, pinnae; downy.
Anal hair; short blunted and abraded hair.
Similar to facial hair (beard)
Table 7-2. Types of body hair. Reference: Bisbing, Richard E., in Saferstein, Editor, Forensic Science Handbook, Vol. 1, 2nd
Ed., Prentice Hall, 2002.
Tip Analysis
Viewing the tips of hairs give an indication as to how they were removed from the body.
Fallen Out Hairs
Figures 7-14: (above) Notice the bulb of the hairs; the root is intact. These hairs fell out due to natural circumstances.
Figures 7-15 (below): Natural tips of hairs.
Figures 7-16: These hairs have
been forcibly removed. Notice the
excessive tissue on the bulbs.
Frequently Asked Question about Hair
Is it possible to determine where on a human body a hair originated?
In most cases, it is quite easy to identify where on a body a hair originated, even more so when several
hairs are available. Head hair has a smaller diameter than hair from the rest of the body and is more
evenly colored. Hair from the legs and trunk contain more medulla than head hair, and exhibit a less
uniform distribution of pigment. Pubic hairs are short, curly, and have a much more pronounced
medulla. Facial hair is coarse and may have a triangular cross section, with blunt tips as a result of
trimming and shaving.
Can the race be determined from the examination of a hair?
In some cases it is possible to identify the race of an individual through an examination of a hair. This is
usually accomplished by observing some general characteristics of the hair from different races. For
example, Negroid hairs are normally kinky, containing dense, unevenly distributed pigments. Caucasian
hairs are straight or wavy, with very fine to coarse pigments that are more evenly distributed when
compared to Negroid hair. Sometimes a cross-sectional examination of hair may also aid in the
identification of race. Cross sections of hair from Caucasians are oval to round in shape, whereas cross
sections of Negroid hair are flat or oval in shape. Due to the lack of pure genealogies in the United
States, these observations are trivial at best. However, if an adequate sample is present to perform an
examination of the DNA, then specific information may be determined about the donor’s racial origin,
and the origin of his ancestors.
Can the age or sex of a person be determined by examining their hair?
The age of an individual cannot be determined from a hair examination, except with infant hair. Infant
hairs are fine, short in length, and have fine pigment. In the past, the dyed or bleached hair may have
suggested hair from a female. But, present hairstyles make these conclusions less likely. The recent
development of mtDNA (mitochondrial DNA) analysis has made it possible to determine the sex of an
individual by the examination of a single hair.
However, because the procedure is so time consuming and expensive, it is not often utilized. If a hair
has attached skin or blood, or is accompanied by several hairs, then DNA can be used to determine the
sex of the suspect.
Is it possible to determine if hair was forcibly removed from the body?
A microscopic examination of the hair root may establish whether the hair has fallen out or has been
pulled out of the skin. A hair root found to have follicular tissue (root sheath cells) adhering to it, as
shown on the following page, is indicative of a hair that has been pulled out.
Hair naturally falling off the body will show a bulbous-shaped root, free of adhering tissue.
However, the absence of sheath cells cannot always be relied upon for correctly judging whether or not
hair has been forcibly pulled from a body. In some cases the root of a hair may be devoid of adhering
tissue even when it has been pulled from the body. An important consideration is how quickly the hair is
pulled out of the head. Hairs pulled quickly from the head are much more likely to have blood or skin as
compared to hairs which have been removed slowly.
(fallen out)
(fallen out)
(cut)
(torn)
(torn)
(Both are pulled out hairs)
With the exception of mitochondrial DNA, it is not possible to extract DNA from a single hair without
blood or skin attached. Such a sample is referred to as a follicular tag. This would make the
identification of a person by their hair almost exact. The present process is very sensitive, contamination
and mishandling of the hair poses a great threat.