1 / 24

Hairs

Hairs. Trace Evidence. Hair as Physical Evidence. Class evidence Removal indicates physical contact between victim and perpetrator- Locard’s Principle. Hair as Physical Evidence. Not good evidence by itself. Present with other evidence it becomes stronger. Hair as Physical Evidence.

carlos-armstrong
Download Presentation

Hairs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Hairs Trace Evidence

  2. Hair as Physical Evidence • Class evidence • Removal indicates physical contact between victim and perpetrator- Locard’s Principle

  3. Hair as Physical Evidence • Not good evidence by itself. • Present with other evidence it becomes stronger

  4. Hair as Physical Evidence • Compare hairs by color and structure • Extract DNA from (if present) root for comparison – Individual evidence. **Now hair is excellent evidence

  5. Characteristics of Hair • Appendage of the skin • Grows out of the hair follicle • Length of hair extends from follicle → shaft → tip • Follicle (root) contains DNA

  6. Hair Shaft • Three layers: • Cuticle: surface of hair • Cortex: main body, contains pigment • Medulla: hollow core

  7. Hair Diagram

  8. Cuticle : Outer Layer • Transparent, outer layer • Scales point down from younger end towards older ends of hair

  9. Cuticle : Scale Patterns Human Hair BatHair Mink Hair Human or Animal Hair

  10. Cortex: Color Layer • Largest part of hair shaft • Melanin = pigment granules

  11. Cortex: Hair Pigmentation

  12. Properties of the Medulla • Medullary index (ratio of medulla:shaft) • Pattern (continuous, interrupted, or absent) • Shape (human vs. animal)

  13. Human Medulla Patterns Interrupted Absent Continuous

  14. Answers from Hair • Body area • Racial origin • Age and Sex (infant vs. adult, DNA from root for gender) • Forcible removal (more sheath cells)

  15. Body Area • Head (scalp) • Eyebrows and eyelashes • Beard and mustache • Underarm • Auxiliary or body hair • Pubic hair Pubic Hair Beard Hair Limb Hair

  16. Racial Origin African American Asian Caucasian (European)

  17. Scissor-cut Broken Burned Razor-cut

  18. Dyed Hair Lice Egg Case

  19. DNA Evidence • Root: nuclear DNA • Shaft: mitochondrial DNA (mtDNA)

  20. Growth Stages of the Hair: • Anagen Stage:  The active growth phase of the hair follicle.  • Catagen Stage:  The transition period between growth and rest.  Hair continues to grow, but at a decreasing rate.  The root bulb looks elongated from being pushed out of the follicle. • Telogen:  The rest period for the follicle.  The current hair is shed and no new growth takes place for a period of time.

  21. Hair as Forensic Evidence

  22. Hair Collection • Collected from crime scene by plucking, shaking and scraping surfaces • Use tape over small surfaces • Vacuum large surfaces • Initial analysis performed under compound microscope • Collect 50 hairs from suspect for comparison. Not all hairs are the same

  23. Testing For Chemicals • Neutron activation analysis (NAA) – identify 14 different elements in hair • Antimony, argon, bromine, copper, gold, manganese, silver, sodium, zinc • Hair grows about 1.3 cm per month – calculate timeline for exposure to toxins or poison

More Related