How is hair analysis junk science? Maybe you just mean that people misuse the facts to come to incorrect conclusions?

It's only supposed to be used to include or exclude someone, and based on the numbers/probabilities it's generally only useful for excluding someone. Of course that's not how most prosecutors use it...

Hair analysis, as in looking at two hair samples under a microscope and determining if they are a match, is definitely junk science. The FBI has specifically acknowledged this, dozens of cases have been overturned because subsequent genetic testing has shown hair samples did not, in fact, match. In at least one case someone was convicted based almost entirely on hair sample analysis, and later DNS testing showed that not only was the hair not a match, the hair found at the crime scene belonged to a dog. https://www.nemannlawoffices.com/blog/fbi-forensics-convicte...