CHEM 207 - Chapter #8 - Trace

CHEM 207 - Chapter #8 - Trace - Trace suspect 1 Trace...

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1 Trace Evidence Trace Evidence Hairs, Fibers and Paints Hairs, Fibers and Paints Trace suspect 1 Trace suspect 2 Trace suspect 2 Trace suspect 3 Trace suspect 3 Trace suspects at the scene Trace suspects at the scene Background Background All previous chapters have set the stage for the evidence analysis Trace evidence analysis holds the key to many successful case resolutions PDF Created with deskPDF TS PDF Writer - DEMO :: http://www.docudesk.com
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2 Morphology of Hair Hair often found at scene Individual characteristics of hair (chemical and physical) difficult to isolate. Hair is important, provides strong corroborative evidence for placing person at crime scene What is Hair? Hair is an appendage of skin Grows out of the hair follicle (a body organ) Three layers of interest Three layers of interest Medulla Cortex Cuticle What is Hair? What is Hair? Hair not easily destroyed, therefore useful for personal identification and comparison Use microscope to observe and compare hairs Cuticle Cuticle Outside covering of hair Formed by overlapping scales (cuticular scales) that surround shaft, cortex, and medulla Scales form from pigment free cells that have hardened and flattened as hair grows Scales act as a protective layer Cuticle Beaver scale Wild hair, human Scale cast impression Scale type, imbricate PDF Created with deskPDF TS PDF Writer - DEMO :: http://www.docudesk.com
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3 Cortex Cortex Composed of spindle shaped cell aligned in a regular array, parallel to length of hair Hair color due to pigment granules interspersed in cortex Hair color dependent on kind and amount of pigment present in cortex Cortex Microscopically, see only black, brown and yellow pigment granules Shade of hair depends on amount of granules present Exceptions: true blonde or true red hair (coloring from phaeomelanin or trichosiderins, respectively) Cortex Cortex Cortex, pigment granules medulla Hair natural and dyed, 800x Hair, dark, human Hair, dark, human Pigment granules Medulla Medulla Collection of cells having the appearance of a central canal running through hair Very broad/wide in animals (other than human), greater than half diameter of shaft Human medulla narrower Medulla Compare medullary index when analyzing hair samples Help determine human vs. non-human hair Medullary Index- Ratio of medulla diameter to diameter of hair shaft Not all hairs have medulla PDF Created with deskPDF TS PDF Writer - DEMO :: http://www.docudesk.com
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