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Chp. 10 Hair Analysis
PLEASE DO NOW
1. How many hairs does the average person have on his/her head?a) All
b) Brown hair
c) Red hair
d) Blond hair
2. What information can a forensic scientist determine from a human hair?
Hair as Evidence
• Continually falls from the body– About 100 hairs fall out each day
• Not readily lost or displaced• Goes unnoticed by criminal• Not easily destroyed• Useful associative evidence since it
originates directly from the individual
Hair Structure
• Hair = epidermal appendage that grows out of the skin from an organ known as the follicle– Root = portion of hair that lies in follicle
• Bulb = enlarged base of root• Dermal papilla = connective tissue
surrounded by bulb– Shaft = portion of hair above skin’s surface
• Composed primarily of keratin• Feature unique to mammals
Hair Growth
• Average period of hair growth 1,000 days– Grows 1 cm per month
• 3 distinct growth phases– Anagen (80-90% of hairs)
• Follicle actively producing hair– Catagen (2% of hairs)
• Transitional period– Telogen (10-18% of hairs)
• Follicle dormant/resting
Hair Growth
• Anagen Phase– Cells in dermal
papilla undergo mitosis and grow up to form hair shaft
– Bulb is described as flame shaped
Hair Growth
• Catagen Phase– Cells in the shaft
continue to differentiate but no more pigmentation or color produced in hair towards root
– Bulb of the root shrinks and becomes surrounded by the club – a capsule of cells
Hair Growth
• Telogen Phase– Hair anchored in
follicle only by club– Germ cells below
club getting ready to form next hair
– Dermal papilla looks like a ball below germ cells waiting to be surrounded by next bulb
Hair Structure
• The shaft of the hair has 3 layers– Cuticle = thin translucent scale layer
surrounding shaft– Cortex = main body of hair shaft– Medulla = central canal-like structure
Cuticle
• Made up of overlapping, nonnucleated, pigment-free, keratinized cells that have formed scales– As many as 6 layers of scales per hair– Scales always point away from the root
• Outer and inner cuticle margins can be:– Cracked– Ragged– Serrated– Flattened
Cuticle
Cuticle
• Viewing cuticle scales– Mount hair between
glass slides– Prepare a clear cast
of the cuticular surface
– Scanning electron microscope
Cortex
• Composed of elongated keratinized filaments aligned together parallel to the length of the hair
• Contained within cells of cortex– Cortical fusi = delicate air spaces
• Vary in amount, size, shape and distribution• Appear dark with transmitted light and bright with
direct light– Hair pigment = solid structure that gives hair color
• Vary in size, shape, distribution and density• Appear dark and granular• Smaller than cortical fusi
– Ovoid bodies• Solid structures that are oval in shape• Larger than pigment granules
Cortex
Cortex
Medulla• Cellular column running
through the center of the cortex
• Function is to increase protective properties of hair by adding internal space
• Medulla structure on humans is amorphous
• Pattern can be absent, fragmental, interrupted, or continuous
• Appearance will vary from person to person and within hairs of the same individual
Medulla
Hair as Evidence• Class evidence• Have to compare evidence against reference
samples• To collect samples:
– Bright light aids in the visualization of questioned hairs at a crime scene
– Stored in paper packets or between sealed glass slides
– Wide transparent tape obtains difficult to see hairs from clothing and carpets
– Note location from where collected• To collect reference samples:
– Collected from both victim and suspect– About 50 samples collected for comparison– Should be combed and pulled to represent all
growth stages– Should be taken from each region of the area– Must represent any chemically treated areas of the
hair
Identification of Human Hair
• First step in the forensic investigation of human hair is to identify the hair in question in the following categories:– Species Origin– Racial Origin– Somatic Origin
• A direct comparison with a reference hair can only be made after the hair is classified in this way
Species Origin
• 3 Types of Animal Hairs– Vibrissa
• Tactile and sensitive whiskers• Largest and longest hairs on body usually
– Bristle/Guard• Coarse hairs that make up the protective
outer coat• Distinctive in appearance and morphology
between different animal families– Wool/Fur
• Fine short hairs that cover the body and make up the inner coat
• Provides insulation from wet and cold
Species Origin
• 4 Types of Human Hairs– Primordial
• Coarse and whisker like• Appear during 3rd month of gestation• Grow on upper lips, eyebrows, palms and soles of
fetus– Lanugo
• Fine, soft, unmedullated and unpigmented• Replace primordial hairs but shed after 6 months of
gestation– Vellus
• Fine, soft, unmedullated and short (2 cm)• Spread uniformly over body surface except for
palms, soles, lips, and nipples– Terminal
• Replace vellus hairs at specific sites and stages of life
• Scalp and eyebrows, pubic areas, face, chest, back, arms and legs
Species Origin
• Cuticle– Human
• Imbricate scales = scales are small, flattened and with little serration
– Animal• Exhibit a wide range of cuticular patterns
Species Origin - CuticleHuman Hair – Imbricate
ScalesMink Hair – Spinous Scales
Bat Hair – Coronal Scales
Species Origin
• Cortex– Human
• Untreated human hair is uniform in color• Pigmentation granules are evenly distributed
or slightly more dense toward cuticle – Animal
• Hairs exhibit rapid color changes along the shaft called banding
• Pigmentation granules are more dense toward the medulla
Pigment Distribution in Human Hair
Pigment Distribution in Animal Hair
Species Origin - Cortex
Species Origin
• Medulla– Human
• Rarely 1/3 width of hair shaft• Structure is amorphous• Pattern can be absent, fragmented,
interrupted, or continuous– Animal
• More than 1/2 width of hair shaft• Distinct medulla structure between
species
Uniserial and Multiserial Ladder Medulla in Rabbit Hairs
Vacuolated Medulla in Dog Hair
Lattice Medulla in Deer Hair
Species Origin - Medulla
Racial Origin
DiameterCross
SectionPigmentation Cuticle Undulation
Caucasian70-100
μmOval Even Medium Uncommon
Asian90-120
μm Round Dense Thick Never
African American
60-90 μm FlatDense and Clumped
- Prevalent
Caucasian Hair
Mongoloid (Asian) Hair
Negroid (African American) Hair
Somatic Origin
Scalp: Head hair, 100-1000mm long, 25-125 um diameter; 0.4 mm/day growth; small root; tapered tip; little diameter variation; various medullation; often with cut tips may be artificially treatedPubic: Pudendal; 10-60 mm long; coarse diameter and prominent diameter variation and buckling; broad medulla; follicular tags common; asymmetrical cross section twisted and may be straight, curved, or spirally tuftedVulvar: Secondary pubic hair; finer and shorter; may be abradedChest: Pectoral; moderate to considerable diameter variation; long fine archlike tip; usually longer than pubic hairBeard: Facial hair; very coarse; 50-300 mm long; large root, irregular structure; often triangular cross section; complex medullation; blunted or razor cut tip; grows 0.4 mm/dayAxillary: Arm pit; 10-50 mm long; grows 0.3 mm/day; coarse; blunt tip, abraded or frayed; usually straighter than pubic hair; many cortical fusi; sometimes yellowed and bleachedEyebrow: 1 cm long; 0.16 mm/day growth; curved; relatively coarse for length; smooth curve with punctuate tip and large medullaEyelash: Ciliary; less than 1 cm long; short curved pointed hairLimb: Leg and arm hair; 3-6 mm long; fine tip; irregularly medullated; often indistinctly and slightly pigmentedEar: Tragi; pinnae; downyButtocks: Anal hair; short blunted and abraded hairNose: Similar to facial hair (beard)
Pubic Hair Limb Hair
Beard Hair
Association of Human Hair
• Characteristics used for hair comparison– Structure– Color– Cuticular Traits– Length– Acquired Characteristics
Structure of Hair
Color of Hair
Cuticular Traits
Acquired Characteristics
Scissor Cut Razor Cut
Split End Broken/Clippers
Microscopy
• 3 types of microscope used:– Stereoscopic Microscope - gross observations of
the hairs• Study trace evidence on the hair’s surface, spatial
configuration, roots, and tips– Compound or Polarizing Microscope - allows for
higher magnification and resolution• Delineates hair’s finer structural characteristics
(pigment, scale, structure, cortical fusi, medulla)– Transmitted Light Comparison Microscope -
compare known and unknown hairs side-by-side
• Mounting choices– Dry mount– Temporary liquid mounting media– Permanent mounting media
Conclusions from Comparisons
• One of 3 conclusions can be reached:– The hairs matched in microscopic characteristics
indicating an association– The hairs were not alike and therefore did not
originate from the same individual– No conclusion can be drawn from the evidence
• Factors affecting degree of certainty associated with conclusion:– Number of unknown hairs found to be similar to
reference hairs– Number of microscopic features observed– The presence of unusual characteristics– Condition of specimens– Completeness of reference sample collection
Was Hair Forcefully Removed?• Look for follicular tag
– Tissue from the follicle attached to the root of the hair
– If a hair pulled from the body was securely attached to the follicle (anagen stage) a follicular tag will be present
• If there:– Yes hair was pulled out
• If absent:– Could have fallen out naturally– Could have been pulled out but cannot tell because
• If the hair was in the telogen phase, no tissue would be attached
• Some individuals lack follicular tissue on plucked anagen hairs
Naturally shed hairs dislodged through combing display
undamaged, club-shaped roots
A hair forcibly removed from the scalp will exhibit stretching and
damage to the root area
(PULLED)
Forcibly removed hairs may have tissue
attached called the follicular tag
Is Hair from a Dead Body?• Look for postmortem banding
– A dark band around the hair near the root where the skin surface meets the hair shaft
– Found on hairs pulled from decomposing skin
• If present:– May indicate that the body was moved after
death
Individualization of Human Hair
• DNA allows for the individualization of hair– Nuclear DNA
• Found in the follicular tag• Will identify hair with one individual
– Mitochondrial DNA• Found throughout cells of hair• Will identify hair to individuals of the same
maternal line
Quick Review
Human hair is one of the most frequently found pieces of evidence at the scene of a violent crime. It can provide a link between the criminal and the crime.
From hair one can determine: If the source is human or animal Race (sometimes) Origin of the location on the source’s body Whether the hair was forcibly removed If the hair has been treated with chemicals If drugs have been ingested
Collect Reference Samples
Identification Comparison DNA
Review of Hair Analysis
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