Forensics - Hair
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| What kind of evidence is hair | class; without the folice left behind the hair can not be used to identify and individual
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| Functions of hair | On mammals regulates body temperature, decreases friction, and protects from the sun
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| Structure of the Hair | Inner medulla, cortex, outer cuticle
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| The Cuticle | the outermost layers covered in over-lapping scales to protect the inner layers of the hair
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| The Cortex | the thickest layer containing most of the pigment giving hair its color, distriutation of pigment between person to person varies
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| The Medulla | can be hollow or filled, absent, fragmented, continuous, doubled, pigmented, or un-pigmented
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| Different types of hair | cross section can be: cicrular, triangular, irregular, or flattened influencing the curl of the hair
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| Texture | can be coarse or fine
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| Regions where hair can grow | head, eyebrow/eyelashes, mustache/beard, underarms, arms/legs (auxilary), pubic
Distiguishable by the cross-sectional shape
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| 3 stages hair goes through (anagen) | anagen - longest stage in which hair grows while the follicle rapidly divide and deposit materials in the hair
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| 3 stages hair goes through (catagen) | hair grows and changes
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| 3 stages hair goes through (telogen) | during this stage the follicle becomes dormant: during this stage hair is easily lost
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| Life Cycle of Hair | grows around 1.3cm/month 0.44mm/day
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| Linking hair to suspects | Bleaching-disturbs the scales cuticle and removes pigment leaving hair brittle and a yellowish color Dyeing-colors the cuticle and the cortex of the hair shaft.hair grows each day treated hair will have a specific characteristic in common w/his/her hair
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| Hair in different races | physical characteristics that can be associated with certain groups however they dont always apply, also at times it will be impossible to group certain hairs because of a lack of characteristics and poorly defined measures
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| Ways to tell the difference between animal and human hair | pigmentation - tends to be more dense in animals near the medulla while it is more dense near the cutile in human, medullary index often is much thicker in animals than human, hair also can change colors in banded patterns cuticle of hair shaft
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| Medullary measure | Medullary index - diameter of medulla / diameter of entire hair
.50 or more animal
.50 or less human
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| Differences in human and animal | cuticle in animals has a spinous(resembles petals) or coronal (stack of crowns)
Cuticle in humans often imbricate (flattened and narrow)
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| Using Hair in investigation | Locard's principle
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| Testing for substances in the Hair Shaft | Chemicals that the skin absorbs often can be detected by analysis of the hair shaft.
A forensic scientist can perform chemical tests for the presence of various substances.
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| Testing for substances in the Hair Shaft cont. | The hair shaft can be examined in sections to establish a timeline for exposure to toxins.
Neutron Activation Analysis (NAA) can determine concentrations of substances in the sample.
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| Microscopic Assesment | performed first becasue cost effective and quick
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| Testing the Hair follicle | if air is forcibly removed may have "follicular tag
Blood and tissue attached to the follicle may be analyzed
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| Testing the HAir follicle cont. | if blood is found on the follicle it can be lood tested and perhaps show what type it is
if a microscopic match is found the DNA analyzed can be used to provided identification with a high degree of confidence
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Created by:
mpolizzi1
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