chapter 8 hairs & fibers. hair appendage of the skin grows from hair follicle color &...
TRANSCRIPT
Chapter 8
Hairs & Fibers
Hair Appendage of the skin
Grows from hair follicle
Color & structure are important forensic features
Composed of 3 layers
Hair Shaft Layers
Cuticle Outside covering
Made of scales
Different species different scale patterns
Cortex
Main body of hair
Contains pigments that give hair its color
Medulla
Central canal
Varies in thickness (by species)
Not present in all hairs
Types of Medullas
Continuous:
Interrupted:
Fragmented:
Absent
Hair Growth
Occurs at root
Grows at a rate of 1 cm/month
3 phases: Anagen Catagen Telogen
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
Catagen Phase
Growth slows
Follicle breaks down
Root bulb shrinks
Lasts 2 – 4 weeks
Telogen Phase Resting phase
Growth stops
Hair falls out
Root bulb club shaped
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**
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
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
Special Note
Hair is an important piece of
evidence, BUT is only 100%
when DNA is analyzed!!!
Fibers Can be natural or man-made
Important in homicides, assaults, & sexual offenses (Cross-transfer)
BUT mass production of fabrics has evidential value
Natural Fibers Come from animal or plant sources
Wool Sheep Cashmere Goat Mink
Cotton Plant Twisted, ribbon-like shape
Man-made Fibers
Rayon (1911) Nylon (1939) Polyester Acrylics Spandex
Identification of Fibers Try to trace their origin
Examine color & diameter with comparison microscope
Look for striations & cross-sectional shape
Determine dye composition
Collection & Preservation
Remove fibers with clean forceps
Package articles of clothing separately
Use adhesive tape lifts on carpet, rugs, & bedding