1. Hair & Fibers

2. Class vs. Individual Evidence
Hair is considered class evidence unless
DNA can be isolated from the root.
Remember:
Class evidence can only be connected to a group
Individualized evidence can be connected to a unique source.

3. Locard’s principle
When two objects come into contact, material is exchanged.
How much material is transferred is affected by
Intensity of contact
Duration of contact
Type of surfaces

4. Questions to ask about trace evidence (hair and fibers)
1. What is it?
2. Man-made or natural?
3. What is its source?
4. How common is it?
5. Can it be identified to a single source?

5. Equipment Stereomicroscope Compound microscope
Phase contrast microscope
Scanning electron microscope
Comparison Microscope
FTIR- Fourier Transform Infra Red Spectrophotometer
GC- Gas chromatograph

6. Why is human hair useful in forensics?
Sheds easily
Clings to clothes
Lasts for long periods of time
Toxins (esp. heavy metals) are deposited in hair. You can estimate the time of poisoning based on the growth rate of hair)
Case study: Robert Curley case from Wilkes-Barre

7. Human Hair
scalp
pubic
eyebrow & eyelashes
beard
chest
arm
leg

8. Structure of Hair Follicle= pocket of cells where hair grows Cuticle
Cortex
Medulla

9. 1. Cuticle- overlapping scales always point up the shaft of the hair
2. Cortex- internal body, pigments
3. Medulla- inner core
Smaller in humans than in animals

10. Types of cuticles Coronal – common in mice, rats
Spinous(petal) – triangular shape, found in cats - makes cat hair stick to other materials easily
Imbricate (flat) – humans

11. Cortex
Contains pigment of the hair

12. Medulla Types
Solid or continuous
Interrupted
Fragmented

13. How to match hairs Consider: 1. color and width 2. medulla type
3. cuticle type
4. shape of hair in cross section

14. Hair in cross section Armpit ----- oval Beard ----- triangular
Head round
Eyelashes and brows taper

15. Sources of Animal Hair Living animal Pelt Wool sweater
Often pet hair transferred during crime

16. Fibers Small, elongated pieces of material used to make: Cloth Carpet
Paper
Cardboard
Rope
String

17. Fibers Classification: a) Natural- animal hairs (wool)
- excrement (silk)
- plant (cotton)
- mineral (asbestos)
b) Man-made
nylon
polyester
rayon

18. Fibers Sorted by: Color Fluorescence Thickness Water retention
Cross-section
FTIR
Chromatography of dyes