1. Trace Evidence
Hair & Fiber

2. Collection of Hair & Fiber Evidence

3. To remove a fiber from an object:
Preservation/Collection of CARRIERS of hair & fiber evidence rather than the actual hairs/fibers
Hair samples must also be collected from victims of suspicious deaths during autopsy
To remove a fiber from an object:
Use clean forceps
Place it on a small sheet of paper
Fold (druggist) and label paper
Place packet inside another container

4. Hair Evidence

5. Hair Evidence (Class Evidence)
Comparison of microscopic characteristics of questioned hairs to known hairs can provide strong corroborative evidence for placing an individual at a crime scene
properly collected
accompanied by adequate standard/reference samples
50 head samples
24 pubic samples

6. Hair Evidence – 2 Step Process
Identification of Questioned Hairs
Hair Examination:
Animal vs Human
Type of Animal
Comparison of Questioned & Known Hairs

7. Hair Morphology Grows out of hair follicle Root – embedded in follicle
Shaft – length of hair; subjected to most intense examination
3 Layers
Cuticle
Cortex
Medulla
Tip – end of hair

8. 3 Layers of the Shaft
Cuticle – scale structure covering exterior of shaft
Always point towards the tip
Useful in species identification
Cortex – main body of hair shaft
Embedded with pigment granules
Color, shape, distribution of pigments provide points of comparison

9. 3 Layers of the Shaft
Medulla – cellular column running through the center of the hair
Continuous
Interrupted
Fragmented
Absent

10. Human Vs Animal Hairs Medullary Index
Diameter of the medulla relative to the diameter of the hair shaft
For Humans, less than 1/3
For Animals, usually ½ or greater
Medulla Structure
Uniserial
Multiserial
Vacuolated
Lattice
Amorphous
Scale Patterns
Coronal (crown like)
Spinous (petal like)
Imbricate (flattened)

11. Human Vs Animal Hairs
Human hair exhibits ONLY an imbricate scale pattern
Some humans don’t have a medulla
Humans have less than 1/3 medullary index
Animal hair can have all three
Animals have medulla
Animals have ½ or greater medullary index

12. Human Hair Cross-section shapes of hair can help suggest racial origin
Circular
Oval
Flattened
Body Area Determination
Head hairs – longest, uniform diameter, cut tip
Pubic hairs – coarse, wiry, diameter variation
Facial hairs – coarse, triangular cross-section
Limb hairs – short, arc-shaped, tapered

13. Hair Growth
Anagen Phase – hair is actively growing; materials are deposited in the hair shaft
Catagen Phase – transition between anagen & telogen phases
Telogen Phase – resting phase; natural shedding will occur during this phase
Hair forcibly removed during the Anagen Phase will exhibit a damaged root tip – follicular tag
DNA Analysis of follicular tag - individualization

14. Fiber Evidence
A fiber is a smallest unit of a textile material that has a length many times longer than its diameter

15. Types of Fibers (Class Evidence)
Natural Fibers – derived from plant & animal sources
Wool
Mohair
Cotton
Cashmere
Manufactured Fibers – man-made
Regenerated Fibers – manufactured from natural raw materials
Rayon
Synthetic Fibers – made from synthetic chemicals
Nylon
Polyester

16. Fiber Evidence Examination
Torn fabrics that can be exactly fitted in a jigsaw-puzzle type manner – individualization
Microscopic Examination
Color
Diameter
Lenghthwise striations
Delustering particles (to reduce shine)
Cross-Sectional shape
Dye Analysis

17. Fiber Evidence Fibers can Occur naturally Be man-made
Be spun with other fibers to form a yarn, which is woven
Be knitted to form a fabric

18. Natural Fibers
Many different natural fibers originate from plants & animals
Plant
Cotton
Flax (linen)
Jute
Hemp
Animal
Wool
Alpaca
Cashmere
Mohair
Cotton and Wool are the most common plant and animal fibers
Less common fibers have increased significance
Cotton Fibers
Wool Fibers

19. Man-Made Fibers
More than half of all fibers used in production of textile materials are man-made
Some man-made fibers originate from natural materials such as cotton or wood
Others originate from synthetic materials

20. Man-Made Fibers Most common: Polyester Nylon Next most common: Acrylic
Rayon
Acetate
The shape of a man-made fiber can determine the value placed on that fiber
Some cross-sections are more common than others & unusual ones make a fiber more significant
Cross-sectional
views of nylon
carpet fibers as
seen with a
scanning electron microscope (SEM)

21. Fiber Evidence Fiber Color
Often several dyes are used to give a fiber a desired color. Individual fibers can be colored prior to being spun into yarns.
How color is applied and absorbed along the length of the fiber are important comparison characteristics.
Color-fading and discoloration can also lend increased value to a fiber association

22. Fiber Evidence Fiber Number Fiber Location
The greater the number of fibers, the more likely that contact actually occurred between these individuals
Fiber Location
The location of fibers on different areas of the body or on specific items at the crime scene influences the significance of the fiber association

23. Assigning Significance
When a fiber examiner matches a questioned fiber to a known item of clothing, there are only two possible explanations:
The fiber actually originated from the item of clothing
In order to say that the fiber originated from the item of clothing, the clothing either had to be the only fabric of its type ever produced or still remaining on earth, or the transfer of fibers was directly observed
The fiber did not originate from the item of clothing
Since neither of these situations is likely to occur or be known, fiber examiners will conclude that the fibers could have originated from the clothing or that the fibers are consistent with originating from the clothing.

24. Assigning Significance
Another important consideration is coincidence.
When fibers that match the clothing fibers of the suspect are found on the clothing of a victim, two conclusions may be drawn:
The fibers originated from the suspect
The fibers originated from another fabric source that not only was composed of fibers of the exact type and color, but was also in a position to contribute those fibers through primary or secondary contact.