Hair Structure
This is the outermost layer of the hair made of overlapping scales.
What is the cuticle?
Hair without the follicle attached is considered this type of evidence.
What is class evidence?
The smallest unit of a textile material.
What is a fiber?
In a flame test, investigators observe burn speed, odor, and this remaining material.
What is residue?
The unusual fibers found on victims were this color.
What is yellow-green?
This layer contains pigment and is the thickest part of the hair.
What is the cortex?
This type of DNA is used when testing a hair shaft without a root.
What is mitochondrial DNA (mtDNA)?
These fibers are typically smooth and shiny.
What are synthetic fibers?
A fiber that melts into a hard bead is most likely this type.
What is synthetic?
The fibers were determined to be this material.
What is nylon?
This central core may be continuous, fragmented, or absent.
What is the medulla?
mtDNA testing only traces this family line.
What is the maternal line?
Cotton is this type of fiber.
What is a natural (plant) fiber?
A fiber that smells like burning hair is most likely this.
What is wool/animal fiber?
Why were these fibers significant to the case?
They were rare and matched carpet in Williams’ home and car.
This structure must be present to obtain nuclear DNA from hair.
What is the follicle/root?
Hair alone cannot definitively prove this in court.
What is identity/guilt?
Fibers most often provide this type of evidence.
What is class evidence?
A white, fluffy ash suggests this type of fiber.
What is a natural plant fiber (like cotton)?
Why was fiber evidence powerful in this case even without DNA?
Extremely low probability of coincidence + multiple matches.
Which hair structure is most useful for distinguishing between species rather than individuals?
What is the cuticle (or medulla)?
Name two features investigators examine under a microscope when comparing hairs.
What is Medulla pattern, cortex thickness, pigment distribution, cuticle scales, root shape, etc.?
Finding multiple cross-transfers between suspect and victim increases the likelihood of this.
What is physical contact/association?
Why is flame testing useful in forensic science?
It helps determine fiber type and narrow possible origin.
Investigators calculated that the odds of both rare fiber matches occurring by coincidence were approximately 1 in 29 million. What does this statistic demonstrate in forensic terms?
It demonstrates an extremely low probability of coincidence, meaning the fiber evidence strongly supported association between Williams and the victims.