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

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

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

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

10. Phases of Hair Growth

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

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