trace evidence
DESCRIPTION
Trace Evidence. Hair. NS2232 - Littlefield. Trace Evidence--any small pieces of material, man-made or naturally occurring Most common examples: Hair Fiber. NS2232 - Littlefield. Questions for Trace Evidence. What is it? Is it man-made or natural? What is its source? How common is it? - PowerPoint PPT PresentationTRANSCRIPT
Trace Evidence--any small pieces of material, man-made or naturally occurring
Most common examples: Hair Fiber
NS2232 - Littlefield
Questions for Trace Evidence
What is it?
Is it man-made or natural?
What is its source?
How common is it?
Can it be identified to a single
source?
NS2232 - Littlefield
From hair one can determine:
Human or animal Race Origin Manner in which hair was removed Treated hair Drugs ingested
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Hair Cuticle Scale Types Mosaic Pectinate Imbricate Petal Diamond petal Chevron
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Hair Cortex
The cortex gives the hair its shape.
It has two major characteristics: Melanin Cortical fusi
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Continuous
Intermittent or interrupted
Fragmented
Absent--not present
Hair Medulla Types
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Medullary Index
Medullary Index for human hair is generally less than 1/3.
For animal hair, it is usually greater than 1/2.
Hair Growth
Anagen--hair that is growing Catagen--hair at rest Telogen--hair that is dying
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Collection of Hair Evidence
Questioned hairs Known/Control Sample
– 50 full-length hairs from all areas of scalp– 24 full-length pubic hairs
NS2232 - Littlefield
Hair ToxicologyAdvantages:
– Easier to collect and store– Is externally available– Can provide information on the
individual’s history of drug use.
Collections must be taken from different locations on the body to get an accurate timeline.
NS2232 - Littlefield