OntarioSasquatch
Microscopy of Hair Part 1: A Practical Guide and Manual for Human Hair
Published in Forensic Science Communications, Research and Technology, January 2004 – Volume 6 – Number 1
Douglas W. Deedrick , Supervisory Special Agent, Scientific Analysis Section
Sandra L. Koch, Physical Scientist, Forensic Examiner, Trace Evidence Unit, Federal Bureau of Investigation, Quantico, Virginia
http://www2.fbi.gov/hq/lab/fsc/backissu/jan2004/research/2004_01_research01b.htm
Human Hairs Identification
Human hairs can generally be identified by racial origin, body area, and other comparison characteristics.
Racial Origin
Key characteristics serve as racial indicators. These indicators are generalities and apply primarily to head hairs. The examiner may encounter hairs that cannot easily be associated with a particular racial model because of poorly defined characteristics, limited size, or inconsistent indicators. These hairs can be identified as apparent racial mixtures or as not classifiable. In spite of an inability to substantiate race, the hair may still be of value for comparison purposes. This racial admixture may serve to further individualize the hair and its source, particularly if the same mixed racial characteristics are observed in both the questioned and known samples.
Caucasian (Figures 24 and 25)
Shaft diameter: moderate with minimal variation (mean diameter for human head hairs - 80um) Pigment granules: sparse to moderately dense with fairly even distribution Cross-sectional shape: oval
Figure 24.
Photomicrograph
of Cross-section
of Caucasian Hair
Figure 25.
Photomicrograph
of Caucasian
Head Hair
Negroid (Figures 26 and 27)
Shaft diameter: moderate to fine with considerable variation Pigment granules: densely distributed (hair shaft may be opaque) and arranged in prominent clumps Shaft: prominent twist and curl Cross-sectional shape: flattened
Figure 26.
Photomicrograph
of Cross-section
of Negroid Hair
Figure 27.
Photomicrograph
of Negroid
Head Hair
Mongoloid (Figures 28 and 29)
Shaft diameter: coarse and usually with little or no variation Pigment granules: densely distributed and often arranged in large patchy areas or streaks Medulla: prominent (often broad and continuous) Cuticle: thick Cross-sectional shape: round
Figure 28.
Photomicrograph
of Cross-section
of Mongoloid Hair
Figure 29.
Photomicrograph
of Mongoloid
Head Hair
Body Area
Certain features of individual hairs identify the region of the body where it originated. The features listed are generalities and align themselves with racial models derived from known samples. Body area can be made with considerable accuracy; however, variations occur that can make this determination difficult. Hairs that fall into this category include those that are immature, transitional, and fragmentary.
Head Hairs
Long with moderate shaft diameter and diameter variation Medulla absent to continuous and relatively narrow when compared to the structure of hairs from other body areas Often with cut or split tips Can show artificial treatment, solar bleaching, or mechanical damage Soft texture, pliable
Pubic Hairs
Shaft diameter coarse with wide variations and buckling (Figure 30) Medulla relatively broad and usually continuous when present (Figure 31) Root frequently with tag (Figure 32) Tip usually tapered, rounded, or abraded Stiff texture, wiry
Figure 30.
Photomicrograph
of Pubic Hair
Buckling
Figure 31.
Photomicrograph
of Pubic Hair
Medulla
Figure 32.
Photomicrograph
of Pubic Hair Root
Limb Hairs
Diameter fine with little variation Gross appearance of hair is arc-like in shape Medulla is discontinuous to trace with a granular appearance (Figure 33) Tips usually tapered, often blunt and abraded, rounded scale ends due to wear (Figure 34) Soft texture
Figure 33.
Photomicrograph
of Limb Hair
Medulla
Figure 34.
Photomicrograph
of Limb Hair Tip
Facial Hairs (Beard/Mustache)
Diameter very coarse with irregular or triangular cross-sectional shape (Figure 35) Medulla very broad and continuous, may be doubled (Figure 36)
Figure 35.
Photomicrograph
of Beard Hair
(Shape)
Figure 36.
Photomicrograph
of Beard Hair
Medulla (Doubled)
Chest Hairs
Shaft diameter moderate and variable Tip often darker in color, long and fine, arc-like Medulla may be granular Stiff texture
Axillary or Underarm Hairs
Resemble pubic hairs in general appearance, but less wiry Medullary appearance similar to limb hairs Diameter moderate and variable with less buckling than pubic hairs Tips long and fine, frequently with bleached appearance
Other Body Hairs
Eyebrow: Stubby, some diameter fluctuation, saber-like in appearance Eyelash: Short, stubby with little shaft diameter fluctuation, saber-like in appearance Trunk: A combination of features of limb and pubic hairs, a transitional hair
Comparison Characteristics
Certain physical features such as sex, size, age, shape, eye color, hair texture, and color can distinguish individuals. None of these features is peculiar to only one individual, but the general appearance and arrangement of these features serves as criteria for identification. There are, likewise, a number of features or characteristics that may be present in a given hair sample that, when considered collectively, provide a basis for association.
There is no criterion for the importance assigned to a particular characteristic. Such a determination can be made only by the individual examiner and must be based on experience. Hair characteristics are not frequently studied because of all the variations in a single sample and the inherent difficulty in assigning standard values for the variations. If, however, particular characteristics are seen in a hair samples that appear with regularity throughout the sample, they must be considered as significant.
The process of identification or association involves distinct stages in the course of an examination. The following 15 different features or characteristics should be considered in the comparison of hair specimens. There are other lists that identify 25 or more hair characteristics, but those lists generally do not disagree in substance with the following, only in the manner of organization.
Race: Features that serve to determine racial origin have been discussed previously. Hairs of a particular racial group can exhibit a significant range in the distribution of microscopic characteristics. The photomicrographs of Figures 37-45 illustrate some of the variation that can be seen in the head hairs of different individuals from different racial groups.
Figure 37.
Photomicrograph
of Head Hair of
Caucasian Individual
Figure 38.
Photomicrograph
of Head Hair of
Caucasian Individual
Figure 39.
Photomicrograph
of Head Hair of
Caucasian Individual
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