Ch. 3 Forensics. I. Why is human hair useful in forensics? SSheds easily CClings to clothes LLasts for long periods of time TToxins (esp. heavy.

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Presentation transcript:

Ch. 3 Forensics

I. Why is human hair useful in forensics? SSheds easily CClings to clothes LLasts for long periods of time TToxins (esp. heavy metals) are deposited in hair. You can estimate the time of poisoning based on the growth rate of hair. CCase study: Robert Curley case from Wilkes- Barre

 Comparison microscope Side-by-side comparison of hairs  Chemical analysis Chemicals absorbed by skin - incorporated into hair Contains ingested toxins (arsenic, lead, drugs)  Neutron activation analysis Can I.D. concentration of up to 14 different elements in 2cm of hair  DNA fingerprinting (need follicle)

 follicle= pocket of cells where hair grows  Cuticle transparent outer layer  Cortex Contains pigment (melanin)  Medulla Center

 overlapping scales always point from proximal to distal end of shaft  Human hair & animal hair differ in type of cuticle Human = imbricate Other mammals Human Deer

B. CORTEX C. MEDULLA  Largest part of hair shaft in humans  Pigment may be evenly or unevenly distributed  Amount of melanin determines hair color  May be hollow, filled with cells, or absent  If present, may be fragmented, continuous, or doubled  Animal hair always has a thicker medulla than human hair

continuous fragmented absent

 Locard’s exchange principle – hair transferred by contact.  Macroscopic characteristics – length, color, curliness  Microscopic characteritsics – medullary pattern & index, pigmentation of cortex, type of scales on cuticle.  Flourescence – dyes and other treatments flouresce under certain colors of light.

 Ingested or absorbed chemicals incorporate into the hair shaft.  Hair is dissolved & substances are released & identified.  A timeline can be established by testing different portions of a hair.  NAA (neutron activation analysis) can be used to test for up to 14 different elements in hair – combo unique to individuals

 Follicular tag may have blood and proteins attached.  May be analyzed for blood type  DNA of follicular cells may also be analyzed. Appearance of hair shaft = class evidence Blood type = class evidence DNA analysis = individual evidence

 Alma Tirtsche (1921)  Eva Shoen (1990)  Napoleon Bonaparte Hair collected – 1805, 1814, 1821 Hair analyzed – 2001 & 2002