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Hair Evidence
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Parts of the Hair
Distal end
Medulla
Cuticle
Cortex
Proximal end
Proximal end of hair is the part that is/was closest to the scalp. Distal end is farthest from the scalp. Cortex is the part of the hair containing pigment. Cuticle is the covering on the hair. Medulla is the pattern down the center of the hair. Follicle is the organ that hair grows from in the scalp.
Follicle
Root
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Medulla Types
Fragmented patterned medulla has no pattern in the breaks found in the medulla. Intermittent has regularly spaced breaks.
Intermittent
continuous
Fragmented
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Medullas
Hair in top image- uniserial ladder medulla pattern
Hair in middle image- multiserial ladder medulla pattern
Hair in bottom image- deer medula
Deedrick, D. W. Hairs, fibers, crime, and evidence, Forensic Science Communications [Online]. (Jan 2004). Available:
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Cuticle Types
Imbricate
human
Spinous
cat
Coronal
mouse
Deedrick, D. W. Hairs, fibers, crime, and evidence, Forensic Science Communications [Online]. (Jan 2004). Available:
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Deedrick, D. W. Hairs, fibers, crime, and evidence, Forensic Science Communications [Online]. (Jan 2004). Available:
Human Cuticle
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Medullary Index
Width of the medulla/ width of the hair shaft
If it is less than 1/3, it is human
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Cortex
Contains pigment granules.
Pigment distribution
Dyed hair
Undyed hair
Undeveloped or missing pigments cause grey hair
Normal hair has unevenly distributed pigment. Dyed hair has pigment that is evenly placed on the hair shaft. Semi-permanent dyes color only the surface of the hair. Permamnent dyes color the entire shaft.
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Proximal End
End nearest torso
Root or no root?
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Distal End
End farthest from the torso
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11. Telogen, Anagen & Categen Phases of Hair
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Observe Cuticle
Type of cuticle
Is this possibly human?
Damaged or undamaged
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Questions About Hair
All hair on one head the same?
Different on different body areas?
Tell race of person from hair?
Sex of person from hair?
Age of person from hair?
Hair varies in any area. Hair on top of your head is the most rough, lightest hair. Underneath, in back is darkest most fine hair. Different in all areas of the head due to difference in exposure to elements and wear and tear.
Hair in different body areas has different characteristics: underarm hair is slightly different from body hair, pubic hair and in post adolescent males, facial hair. Facial hair in male is triangular in its cross-sectional shape.
The are three general ancestries that all people come from: Mongoloid, Caucasian and Negroid ancestries. Hair from pure Mongoloid ancestry is black and more oval or flat in its cross-sectional shape (which makes it more fine and straighter.than the other ancestries. Hair from pure Negroid ancestry is also very full of dark pigment and very round in its cross-sectional shape (making it more curly and coarse than other ancestries). Caucasoid is somewhere in between in its cross-sectional shape and varying in color from pale blonde to red and dark brown.
Since there are virtually no pure ancestries remaining race can not be determined from the structure of hair.
There is no difference in hair from males and females.
Since the development of gray hair has nothing to do with aging, the color of hair tells nothing about its age. However, babies are born with undeveloped hair (no medulla or cuticle). At some point before one year of age babies lose all of their undeveloped hair and it is replaced with hair that is fully developed.
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14. Comparing Hair Samples?
Comparing hair from a scene to hair from a known source?
Is it Similar? What makes it Similar?
All the characteristics found on the known hair and the questioned hair must be identical.
What does it mean to say they are consistent with one another?
Hair has only class characteristics. What doe it mean to say they “match?” Forensic scientists really dislike the word “match.” If hair has all the same characteristics they still have only class characteristics. They can be said to have a similar source. That is hairs from multiple sources have these same characteristics. They can not be separated.
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Class vs. Individual
Hair has basically class characteristics
Matching distribution of pigment, medulla type and cuticle type can be found in many individuals.
Cellar material present
DNA???
In comparing hairs their pigment distribution, medulla pattern and cuticle must be the same in order to say that the two hairs are consistent with one another. If a root is attached to the hair then it has individual characteristics that can allow it to be linked to a a single person with high probability. Without a root hair has only mitochondrial DNA (mtDNA). Mitochondrial DNA allows a hair to be found to be consistent with a suspect and his or her relatives through their mother only. That is, mtDNA has a high probability of matching a suspect, their siblings with the same mother, their mother and their mother’s siblings, etc. Since they could theoretically have many relatives with the same mtDNA, how could a detective limit the number of possible suspects who could have been present at that crime scene in order for their hair to be found? (alibis)
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Hair Collection
Cellophane tape into Petri dish or
Vacuuming
Choose container that will prevent loss
Label and
Seal
Receipt for evidence!!!
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Control Samples
Determine the source of evidence
Uncontaminated
From known source
For hair-must be pulled
50 from all over head
24 from pubic area in case of sexual assault
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