1. Hair and Fiber Analysis

2. Morphology of Hair Part of Integumentary System
Grows out of hair follicle
Hair consists of
Root/bulb
Shaft
Tip end

3. Morphology Cont. Hair Shaft is the focus of most forensic analysis
3 Parts
Cuticle-the scale structure covering exterior of the hair
Cortex-the main body of the hair shaft
Medulla-a cellular column running through the center of the hair

4. The Cuticle in Detail
Resistance to decomposition and retainment of structural features are due to cuticle
Overlapping scales made of hardened cells
Scale pattern not useful in distinguishing humans but can be utilized for species identification

7. Deer Cuticle

8. The Cortex in Detail
Main body of the hair shaft made of cortical cells
Embedded with pigment granules that give color to hair

9. The Medulla in Detail Central canal of the hair
Medullary index- measures the diameter of the medulla compared to diameter of hair shaft
Written as a fraction….humans less 1/3 animals ½ or greater
Medulla can be continuous, fragmented, interrupted, or non exsistent

11. The Root in Detail Allows for hair growth (three phases)
1. Anagen phase- initial growth phase during which the hair follicle actively produces hair
2. Catagen phase- a transition stage between the anagen and telogen phases
3. Telogen phase- the final growth phase in which hair naturally falls out of the skin
Follicular tag is the most important part because it contains the “richest” source of DNA for the hair

13. Misconceptions of Hair
Hair CANNOT be used to identify a single head or body through its structural characteristics
Only if DNA is present can it be matched
Can determine the area of the body that the hair came from
Some racial origins can be determined from hair
Age and sex cannot be determined (exception infant hair or dye)

14. Fiber History
Most fibers originally came from natural resources: plants and animals
Post 1920 scientist created dozens of new fibers

15. Types of Fibers Natural Fibers—animal or plant sources Sheep—wool
Goats—mohair, cashmere
Camels, Llamas, Alpacas, mink, rabbit, beaver, and muskrat
Cotton

19. Types of Fibers
Manufactured Fibers—fibers derived from either synthetic or natural polymers
First of these were made from materials derived from cotton or wood pulp
Pure cellulose is extracted from them
Also called regenerated fibers
Rayon, acetate, tracetate (all come from cellulose)
Currently many are made solely from chemicals and are called synthetic fibers
Nylons, polyesters, acrylics

20. Rayon

22. Natural and Synthetic Manufactured
Cellulose—natural carbohydrate polymer
Synthetics– polymers are the basic unit of these fibers

23. Identification and Comparison of Manufactured Fibers
Origin of the fiber is key in utilizing it as a piece of evidence
First step is a microscopic examination
Look at the color, diameter, and longitudinal striations
Cross sections of the fibers can also be beneficial to tying fiber back to the manufacturer

24. Cross Section

25. Identification and Comparison of Manufactured Fibers
Microspectrophotometer- compare colors of fibers through spectral patterns
Chromatographic- analyze the dye composition by extracting dye from fibers themselves

26. Identification and Comparison of Manufactured Fibers
Fibers need to have the same chemical composition
Nylon and subgroups of nylon
Acrylic fibers can be broken down into 24 different groups

27. Identification and Comparison of Manufactured Fibers
Birefringence-- polarize white light passing though a synthetic fiber is split into two rays that are perpendicular to each other
Infrared Absorption– polymers that make up fiber selectively absorb infrared light in a characteristic pattern

28. Collection and Preservation of Fiber Evidence