Classifications
What is the two main types of fiber?
Synthetic (Man-made) and Natural
Francisco has hair that is 15cm long. He has some noticeably weak and damaged hair potentially resulting from poison. The healthy section of her hair measures 3cm long. How long ago did the poisoning start?
9.2 months ago
What type of evidence is hair?
class evidence if without the follicle due to the fact that we can still make observations on the type, texture, and color.
What type of evidence is fiber? 4 types
Circumstantial physical trace and class
What do you use to pick up hair and fibers?
Tape, vacuums, and forceps
What are the two parts of a hair and what do they do?
Follicle: contains DNA
Shaft: the body of the hair that protects the insides
Jenny has some noticeably weak and damaged hair potentially resulting from poison. The healthy section of her hair measures 7cm long. The unhealthy part of her hair is 10cm long. How long is her hair?
17cm long
What areas must we collect hair from?
Body, head, public, underarm, beard/mustache, eyelash/eyebrow
DOUBLE JEOPARDY
What is the purpose of hair. At least 2
Regulate body temp
decrease friction
protect against sunlight
act as a sense organ
What test should you use when you have more than one fiber as evidence?
Burn it or submerge it in acid
What are the three natural fibers? Explain
Animal: hair, fur, webbing
Seeds: cotton
Minerals: asbestos
Tony has hair that is 33cm long. She has some noticeably weak and damaged hair potentially resulting from poison. The unhealthy section of her hair measures 10cm long. How long ago did the poisoning start?
7.8 months
What are the two differences between human and animal hair?
Human hair has pigmentation denser towards the cuticle, animals have pigmentation denser toward the medulla
The medulla is larger in animals than in humans
What questions would you ask about the number of fibers found?
How many fibers were found? More fibers suggest possible violence or longer period of contact
What test do you use to test for substances in hair? Explain
Neutron activation analysis: a technique that can identify up to 14 different elements in hair to find the chemical composition. This is used to compare hairs and find if they are identical
What are the three parts of a hair shaft? Explain.
Cuticle: outer part of the hair that protects the rest
Cortex: the mid part of the hair that give the hair pigmentation
Medulla: middle of the hair
Bob has hair that is 20cm long. She has some noticeably weak and damaged hair potentially resulting from poison. The healthy section of her hair measures 19cm long. How long ago did the poisoning start?
0.8 months ago
Explain the life cycle of hair.
Anagen: Active hair growth
Catagen: hair goes through changes
Telogen: Hair stops growing and is prone to falling out
Why is early collection of fiber critical?
Within 24 hours, an estimated 95% of all fibers have been lost
What tests should you do when you only have one fiber as evidence?
Polarizing light microscopy: uses a microscope with a special filter that allows scientists to look at the fiber using special light wavelengths
infrared spectroscopy: emits a beam of light that bounces off the material and returns. How the beam of light has changed reveals the chemical structure of the fiber
What are all four examples of synthetic (man-made) fibers?
Polyester, nylon, acrylic, olefins
2+2-1
3 quick mats
What are the different types of medulla?
Continuous: one unbroken line of color
Interrupted: pigmented line broken at regular intervals
Fragmented: pigmented line unevenly spaced
Solid: pigmented area filling both the medulla and the cortex
None: no medulla
What questions would you ask about: type of fiber?
What is the composition of the fiber? How common or rare is it?
What is direct and secondary transfer?
Direct transfer: transfer of evidence from one person to another
Secondary transfer: transfer of evidence from a source to a person to another