Hair can offer important information to criminal investigations. While hair can never be used as a sole indicator of guilt, hair can offer toxicology information as well as information such as whether the hair dye was used by the donor. The six main methods of hair collection are reviewed and include the use of clear tape, shaking or brushing a garment, and combing loose hairs. Hairs are analyzed as a whole and as a cross section. Hairs contain a root, shaft, and tip, all of which offer potential information to investigators. For example, the tip of a hair may indicate that a chemical treatment was used, suggesting that it is head hair and that the owner used hair dye or other chemicals. The root of hairs may contain follicular tissue, which is the richest source of DNA. The value of hair to forensic investigations cannot be overlooked and, in fact, hair is the most common type of trace evidence able to offer insights about crimes.