34 terms

Forensics Trace Evidence Review

STUDY
PLAY
Name 2 REGENERATED fibers
rayon, acetate
Main structures of the hair shaft?
cuticle, medulla, cortex
What does the medulla usually look like in human hair?
absent, amorphous
Classifications of medulla
continuous, discontinuous, fragmented
Differences between a regenerated, synthetic and natural fiber?
regenerated--> semi-synthetic
synthetic--> man-made
natural-->animal or plant
Name 4 NATURAL fibers
cotton, hemp, wool, cashmere, mohair
Name 3 SYNTHETIC fibers
nylon, polyester, acrylics
What does evolution predict about human hair?
it doesn't serve a purpose and we will be hairless in the future
how do you prepare a wet mont slide?
glass slide, put a drop of water on the sample and put a cover slide on top
What are the main classifications of the cuticle?
coronal, spinous, imbricate
What type of cuticle do humans have?
imbricate
What type of cuticle do cats and mice have?
coronal
About how much does human hair grow every month?
1/2 inches
Which fiber is generally twisted..cotton or lycra?
cotton (plant fibers are twisted like cotton and linen)
Where is the pigment in a hair shaft?
cortex
What does amorphous mean?
not a specific shape, inconsistent
What are the 3 stages of hair growth?
anagen, catagen, telogen
Explain the appearance of the root in each hair growth stage.
Anagen --> hair is actively growing and fully attached
Catagen --> root becomes elongated and can be easily dislodged
Telogen --> not attached, when the hair is naturally shed it is club shaped
What is the medullary index for human hair?
less than 1/3
How is the medullary index calculated?
diameter of medulla/diameter of hair shaft
Describe the classification of evidence for hair and fibers.
trace evidence, cannot positively identify a suspect on its own but it can narrow it down
Explain the difference in thermal decomposition test results for wool and polyester.
wool changed the lead acetate and red litmus paper and the polyester only changed the blue litmus paper
What are other types of trace evidence?
fiber, glass, metal, paint fragments
What is a hair follicle?
an organ under the skin where the root of the hair fiber is
What growth stage is richest in nuclear DNA?
anagen
What structure is richest in mDNA?
medulla
How long does each growth stage last?
Anagen (up to 6 years) Catagen (3-7 weeks) Telogen (up to 6 months)
What is happening to the hair in the Anagen stage?
hair is actively growing and receiving blood, drugs and nutrients
What is happening to the hair in the Catagen stage?
Root becomes elongated, end stage of growth
What is happening to the hair in the Telogen stage?
not attached anymore, falls out
The specific protein in human hair is...
keratin
How can you determine the direction of hair growth?
direction of the cuticle, scales always point from root to tip
Draw an amino group of an amino acid.
R - NH2
What does morphology mean?
structure