1. Chapter 8
Hairs & Fibers

2. Hair Appendage of the skin Grows from hair follicle
Color & structure are important forensic features
Composed of 3 layers

3. Hair Shaft Layers
Cortex
Cuticle
Medulla

4. Cuticle Outside covering Made of scales
Different species  different scale patterns

5. Cortex
Main body of hair
Contains pigments that give hair its color

6. Medulla Central canal Varies in thickness (by species)
Not present in all hairs

7. Types of Medullas
Continuous:
Interrupted:
Fragmented:
Absent

8. Hair Growth Occurs at root Grows at a rate of 1 cm/month
3 phases: Anagen  Catagen  Telogen

10. Anagen Phase Initial growth (lasts 2 – 8 years)
Follicle is actively making hair
Root bulb  flame shaped
**Follicular Tag  Clear tissue around hair (near root)
 BEST source of DNA

11. Catagen Phase Growth slows Follicle breaks down Root bulb shrinks
Lasts 2 – 4 weeks

12. Telogen Phase Resting phase Growth stops Hair falls out
Root bulb  club shaped
No more than 10%
of follicles are in
telogen at any time!!

13. Identification of Hair
Determine whether it’s human or animal
Scale Structure
Medulla Shape
Medullary Index
**Problem  Hairs can vary from one to the next in the same individual**
Help make an ID

14. Comparison of Hair View hairs with comparison microscope
Need standard/reference samples to compare the evidence to  50 head
 24 pubic
Color, length, & diameter must match

15. Hair Evidence CAN Determine …
Place of body origin  head, beard, pubic
Race  but only sometimes
Hair Evidence CANNOT Determine …
Age or sex of an individual

16. Special Note Hair is an important piece of evidence, BUT is only 100%
when DNA is analyzed!!!

17. Fibers Can be natural or man-made
Important in homicides, assaults, & sexual offenses (Cross-transfer)
BUT mass production of fabrics has  evidential value

19. Natural Fibers Come from animal or plant sources Wool  Sheep
Cashmere  Goat
Mink
Cotton  Plant
 Twisted, ribbon-like shape
Animal

20.                       
Cotton
Wool

21.                       
Flax Fibers Viewed
with Polarized Light

22. Man-made Fibers Rayon (1911) Nylon (1939) Polyester Acrylics Spandex
Synthetic

23. Rayon
Nylon

24. Identification of Fibers
Try to trace their origin
Examine color & diameter with comparison microscope
Look for striations & cross-sectional shape
Determine dye composition

25. Cross-section of Man-made Fibers SEM Cross-section
                      
               
Cross-section of
Man-made Fibers
SEM Cross-section
of Nylon Carpet Fibers

26. Collection & Preservation
Remove fibers with clean forceps
Package articles of clothing separately
Use adhesive tape lifts on carpet, rugs, & bedding