What kind of evidence is provided by human and animal hairs, or synthetic fibers?

Answer 1

It provides what the victim was last in contact with; if the hair or substance is unique, it could nail the perp if you have a good match (ex: tri-lobal fibers on a vic and the same consistant tri-lobal fibers in the alleged perps trunk of a car).

On "Medical Detectives" several years ago, a vic and perp were matched through the hair of his cat, which was of a unique breed.

Answer 2

DNA, on the animal and human hair, also texture. Chemical composition of synthetic fibers, and I would suppose treated human hair.