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Hair Evidence

Hair Evidence. Hairs as physical evidence. Valuable because can remain intact for years So strong that they have same tensile strength of steel of same gauge Presence often denotes physical contact. Morphology (Structure) of Hair. Made of keratin -- a protein Consists of: Root (bulb)

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Hair Evidence

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  1. Hair Evidence

  2. Hairs as physical evidence • Valuable because can remain intact for years • So strong that they have same tensile strength of steel of same gauge • Presence often denotes physical contact

  3. Morphology (Structure) of Hair • Made of keratin -- a protein • Consists of: • Root (bulb) • Shaft • Tip http://www.hshairclinic.co.uk/_images/hair_structure.jpg

  4. Root • When pulled from head, some translucent tissue surrounding the hair shaft near the root may be found • Called “follicular tag” http://www.fbi.gov/about-us/lab/forensic-science-communications/fsc/jan2004/research/images/fig58.jpg

  5. Follicular Tags: Can be used for DNA analysis http://hannahc12.files.wordpress.com/2010/04/picture-92.png

  6. Hair Shaft Structure: Cuticle, Cortex and Medulla • 3 sections to a hair shaft • Medulla (interior) • Cortex (main section) • Cuticle (exterior) http://3.bp.blogspot.com/_xvklWrDLexk/S8txNTzoVbI/AAAAAAAACAg/Kbk03aJ5u64/s320/hair-cross-section.gif

  7. Cuticle: scale structure covering the exterior of hair • Formed from overlapping scales that always point towards the tip end • Useful in species identification • 3 basic patterns: • Coronal • Spinous • Imbricate Coronal Spinous Imbricate

  8. Cuticle: scale structure covering the exterior of hair • Coronal: crown-like pattern; like stacked cups • Rodent • Spinous: triangular, petal-like scales • Cat • Imbricate: flattened scales with narrpw margins • Human Coronal Spinous Imbricate

  9. Hair Cortex • Main body of hair shaft • Embedded with pigment granules that give hair color • Can be used to compare hairs of different persons http://www.ecobyte.com.au/a_Basic_Hair_struc_Xsec.jpg

  10. Hair Medulla • Cellular column running through the center of the hair • Can be continuous, interrupted or fragmented http://intro.chem.okstate.edu/chemsource/Forensic/forechem11.gif

  11. Hair Medulla • Presence and appearance varies among individuals • Most human hairs have no or fragmented medulla • Asian hairs may have continuous medulla. http://www.bfro.net/images/whatis/figures/Fig.%203%20with%20caption.jpg

  12. Shape of the medulla • Shape varies by species • Humans: medulla is nearly cylindrical • Animals: • Cat: bead-like • Deer: spherical cells http://www.personal.psu.edu/users/c/l/clv14/sci101/images/standardhair%20copy.jpg

  13. Medullary Index • Varies by species • Calculation: Width of Medulla = MI Width of Cortex

  14. Hair Comparison • Matching color, length and diameter • Can use microscope to distinguish animal hair from human hair • Animals: distinguish using scale structure, medullary index and shape • Humans: • distinguish by looking at presence or absence of medulla. • Distribution, shape and color intensity of pigment granules in cortex

  15. Hair and DNA • Mitochondrial DNA can be extracted from the hair shaft • Inherited only from mother • The root contains nuclear DNA • Only present if hair is forcibly removed

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