Lecture 8: Physical Evidence II (Hair) Flashcards
What is the definition of hair?
Any of the fine threadlike strands growing from the skin of humans, mammals, and some other animals.
Can human hair be individualized through morphology?
No, it is not yet possible to individualize human hair to a single head or body through its morphology.
What partial success has been achieved in individualizing human hairs?
Isolating and characterizing the DNA (nuclear DNA) present in hair.
What can be determined from hair evidence?
- Is it a hair?
- Is it human?
- What area of the body is it from?
- What is the person’s ancestry?
- Is there damage, disease, treatment?
- Is it suitable for comparison?
Name the six types of hair on the human body.
- Head hair
- Eyebrows and eyelashes
- Beard and mustache hair
- Underarm hair
- Auxiliary or body hair
- Pubic hair
Which types of hair are most commonly found at crime scenes?
Hair from the head and pubic region.
What is the structure of hair?
- grows out of hair follicle
- root/bulb, shaft, and tip.
What are the three layers of hair?
- Cuticle
- Cortex
- Medulla
What is the cuticle of hair?
- Scale structure covering the exterior of the hair
- Cannot individualize human hair
- Can make species identification
- Viewed using SEM
True or False: The scale pattern of the cuticle useful for individualizing human hair.
False, only useful for species identification
What pigments are embedded in the cortex of hair, and its purpose?
- Eumelanin and pheomelanin
- Imparts hair with color
- Comparison of hair among diff. individuals
- Can be used for racial determination
What does the medullary index indicate?
D(medulla) / D(hair shaft)
(Medulla is the cellular column running through the center of the hair)
How does the medulla differ between humans and animals?
For humans, the medulla generally occupies less than one-third the diameter of the shaft, while for animals, it is generally one-half or greater.
How can the medulla provide us with racial information?
Summarize general racial determination using hair analysis
What are common damages to hair?
- Breaking
- Burning
- Putrefied roots
- Insect marks
- Cutting
- Crushing
What is a follicular tag?
Translucent tissue surrounding the hair’s shaft near the root, which can be a rich source of nuclear DNA -> Help to individualize hair
What is the significance of the root of the hair?
- Provides nutritions to produce hair and continue its growth
- Along with surrounding cells in hair follicle
What are the three growth phases of hair?
- Anagen
- Catagen
- Telogen
What happens during the anagen phase of hair growth?
It is the initial growth period of hair, lasting up to 7 years, and can yield a rich source of DNA.
What happens during the catagen phase of hair growth?
Transitional phase where hair growth slows and prepares to shed. Lasts from 2-3 weeks
What happens during the telogen phase of hair growth?
The final phase of growth where hair naturally falls out without tissue, lasting 2-6 months. Then the follicle repeats the process with new hair
Summarize the three growth phases of hair
Anagen, Catagen, Telogen
What is the average growth rate of hair?
1.3 centimeters every month.
What is the significance of hair tips?
- Important comparative feature
- Can identify type of treatment and time since cutting
- Take on rounded form in 2-3 weeks
What substances can hair analysis detect?
- Cocaine
- Heroin
- Benzodiazepines
- Amphetamines
What is Neutron Activation Analysis (NAA)?
A technique that can identify up to 14 different elements in a single two-centimeter-long strand of human hair.
What types of DNA can be extracted from hair?
- Nuclear DNA (nDNA)
- Mitochondrial DNA (mtDNA)
Extracted from the root or follicular tag of an anagenic hair
What is the significance of nuclear DNA in hair analysis?
Nuclear DNA can lead to individualization with odds of association typically one in billions or trillions.
What are unsuitable hairs for comparison?
- Damaged
- Too short
- Too light in color
- Fragment
- Extreme treatment
How many hairs should be sampled for comparison?
A minimum of 25-50 hairs from all areas of the head.
If hair is forcibly removed from a victim or suspect, (_)?
- A follicular tag may be present
- Blood and tissue are attached and able to be analyzed for blood type and DNA
True or False: Hair can always provide DNA evidence.
False
Due to the hair growth phase, whether tissue can be collected from hair follicles, and mtDNA V.S. nDNA
nDNA V.S. mtDNA
nDNA: Comes from both parents
mtDNA: Passed only from mother to offspring
