8.2 Notes – Hair continued8.2 Notes – Hair continued

ObjectivesObjectives

• List hair features that are useful for microscopic comparison of human hairs

• Explain proper collection of forensic hair evidence

Identification & Comparison of HairIdentification & Comparison of Hair

• Human hair comparison is not reliable without DNA– Hair exhibits variable characteristics not only

between individuals but within a single individual

• Body area from which the hair originated can be determined – Head hair, pubic hair, beard hair

Identification & Comparison of HairIdentification & Comparison of Hair

• Microscopic examination can distinguish dyed or bleached from natural– Natural end portion different from dyed

portion– Can determine when bleaching occurred based

on distance between the two• Hair grows at 1 cm per month

Identification cont.Identification cont.• Can distinguish between races

– Negroid hair is normally kinky with dense unevenly distributed pigments

• Cross-sections are flat to oval in shape– Caucasian hair is normally straight or wavy

with fine or coarse pigmentation that is more evenly distributed

• Cross-sections are oval to round in shape

Identification cont.Identification cont.

• Cannot be easily determined– Age (with exception of infant hair)– Sex (nuclear DNA from the same can allow

for determination)

• Hair with follicular tissue indicates hair was pulled or brushed out

Identification cont.Identification cont.

• Nuclear DNA from the hair root or follicular tissue can be used to identify a particular person– From the root is easier to obtain DNA in the anagen

phase• Mitochondrial DNA can be used in the absence

of nuclear DNA– Cannot be used to individualize

Collection & Preservation Collection & Preservation of Hair Evidenceof Hair Evidence

1. Must be accompanied by a number of standard/reference samples from the victim, the crime scene, and from suspects

2. Standard hairs must come from the same body area

Collection & Preservation Collection & Preservation of Hair Evidenceof Hair Evidence

3. Standard hairs must be sufficient to represent a sample of hair from one area of the body

4. Generally includes 50 full length hairs from scalp; minimum of 2 dozen full length pubic hairs

5. Hair samples collected from the victim during an autopsy

Case StudiesCase Studies

• Read page 201 and 204– Central Park Jogger Case– Ennis Cosby Murder Case