Comparison microscopes are used to see if a hair sample found at a scene matches a known sample. Examination of hair can also determine the animal family of origin, the body area of origin for human hairs and the method of removal from the body, as well as providing an indication of racial origin. Scalp hair can give the scientist the most information because it usually undergoes the most varied treatments (dying, curling, cutting, hairspray, etc...).

Hair comparison is not conclusive and this is the reason why DNA methods may also be used. Since all nucleated cells in the body contain DNA, hair roots and roots sheaths may be used, and the amount of DNA may be amplified using a method called PCR. The DNA is then typed and a match may be found. The first 10 mm of the bottom of each hair may be used for the DNA testing because it contains the root sheath. Although it does not contain nuclear DNA, the hair shaft may be analyzed for mitochondrial DNA.
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