1. Trace Evidence

2. What do you think trace evidence is? Materials that are small enough to be easily overlooked by a crime scene investigator They are so small they can be transferred (exchanged) by contact or in the air by air currents!

3. Locard’s exchange Principle? When 2 objects come in contact with each other, a cross-transfer of materials occurs When 2 objects come in contact with each other, a cross-transfer of materials occurs

4. Types of Trace evidence Hair Hair Fibers & threads Fibers & threads Metals Metals Paint & other building materials Paint & other building materials Soil, rocks, minerals, & debris Soil, rocks, minerals, & debris String, rope, & containers String, rope, & containers Wood & plant material Wood & plant material

5. Anatomy of Hair Root (internal end) Root (internal end) Medulla Medulla – Inner core – May or may not be present Cortex – main shaft surrounding the medulla Cortex – main shaft surrounding the medulla Cuticle – scaly outer covering Cuticle – scaly outer covering Tip (external end) Tip (external end)

6. Medulla Patterns 1.Continuous – a solid line 2.Interrupted – broken at regular intervals, like the dotted yellow lines on a road 3.Fragmented – broken, but not in a regular pattern 4.Absent

7. Anatomy of Hair

8. Human, cat, Dog, and Mouse Hair

9. What can hair tell us? We know it can tell us whether the hair is human or not. We know it can tell us whether the hair is human or not. If human: If human: – Race – Pulled out or fell out? – Part of the body it came from – How it was cut or dressed If animal, what species? If animal, what species?

10. Phases of Hair Growth

11. Location of Origin Scalp hair Scalp hair – Little diameter variation – More uniform distribution of pigment – No medulla or fragmented Pubic hair Pubic hair – Short and curly – Wide variations in diameter – Continuous medulla Beard hair Beard hair

12. Collecting the Evidence About 40-50 samples from the scalp About 40-50 samples from the scalp About 24 full-length pubic hairs About 24 full-length pubic hairs Need entire hair: Need entire hair: – Variations in color and other features alng length of hair Collected how??? Collected how???

13. Hair Analysis at Work Ennis Cosby Ennis Cosby Central Park Jogger Central Park Jogger – Microscopic analysis vs. DNA analysis

14. Hair Needed! Bring in samples of pet hair! Bring in samples of pet hair! Try to find hairs that have fallen out. (Where should you look?) Try to find hairs that have fallen out. (Where should you look?) Beard hair anyone? Beard hair anyone?