SPLITTING HAIRS: THE ART OF FORENSIC HAIR COMPARISONS

Everyone knows what hair is—there’s no mystery about it. It grows out of your skin and, unlike DNA, is tangible, visible, and often uncooperative. It’s value as evidence, however, is hotly debated. Most people in law enforcement regard it as useless and archaic, while hair examiners think comparisons have gotten a bad rap by attorneys and cops spoiled by the high elimination factor of DNA analysis. If your hero or heroine encounters a hair examiner, they might be defensive of the technique, as well as concerned about job security. In this article I will discuss hair comparisons, the point of which is to determine if a hair came from a particular person. This is completely different from the chemical analysis done to determine drug use, which is an accurate and common technique, but is not used for identification purposes. There is, to date, no chemical means used to identify a hair, for the simple reason that everyone’s hair is basically similar. It’s all keratin proteins held together by extremely strong disulfide bonds. The only way to identify hair (excluding DNA, which I’ll get to later) is visually. You put it on a slide and put the slide under a microscope, and that’s as high-tech as it gets. So a murder has been committed and there’s a hair left at your crime scene. First of all, it’s probably the victim’s. But if the victim is a blond and the hair is dark brown, then you might have a clue. Enter a suspect with dark brown hair. The police officers then need to collect a reference sample—gently or harshly, depending on their mood—of fifty to one hundred hairs. This sounds like a lot, but the average person loses that many per day. The hairs should be both combed and plucked, to obtain roots which have finished growing and end in a neat bulb (telogen) and roots which are still growing, and end in a stretched out tangle (anagen). That way, whether your suspect hair is anagen or telogen, you can compare like to like. Your hair examiner will not mount all these hairs on slides (thank God!), only a ‘representative sample’, trying to get all lengths, thicknesses, and other obvious physical characteristics represented on your sample slides. Slides, by the way, are only 2” x 3” at most, so trying to get a foot-long hair onto one is an exercise in frustration. Hair examiners appreciate buzz cuts. They also appreciate dying and bleaching, which is extremely easy to detect. The hair shaft is one color, then bingo, it’s another.

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