Thursday, February 28, 2019

Hair sideways

Image in public domain, courtesy of Ryan McGuire
In the spirit of full confession, in the past few years I've learned a lot about genealogy research and my own family history, but I've not yet entered the realm of DNA testing. In my naivété on this subject, I've always assumed that if I ever did, the source of my DNA would be a strand or two of hair snipped off my head. That hair, I believed, was my distinctive marker of who I am as a person, especially because it contains my DNA.

Not so, as it turns out. First of all, scientists need to have a strand of hair that is plucked from the head at its root, because the DNA resides at the bulb of the hair, rather than in the shaft.
The hair follicle at the base of human hairs contains cellular material rich in DNA. In order to be used for DNA analysis, the hair must have been pulled from the body -- hairs that have been broken off do not contain DNA. Any body tissue that has not been degraded is a potential source of DNA. (from DNA Forensics Problem Sets)
But even then, it's not foolproof. Take identical siblings, for instance. Their DNA is indistinguishable.

Anyhow, the morphology of hair, that is, the microscopic comparison of hair forms, has been receiving much scrutiny. (Writers of detective novels, take note!) Over time, the use of hair in identifying a person, especially one who's committed a crime, has been a somewhat murky science. In the 18th, 19th, and 20th centuries, hair analysis could be enough to warrant criminal conviction. Even in the early 21st century, Tani Watkins, Richard E. Bisbing, Max Houck and Bonnie Betty published an article titled "The Science of Forensic Hair Comparisons and the Admissibility of Hair Comparison Evidence: Frye and Daubert Considered," which pointed out that, in addition to hair DNA testing: "forensic hair comparisons also provide an excellent means of discriminating between individuals." Perhaps, the argument was posited to validate forensic analysis of hair performed when no DNA was present?

However, an article in the April 2004 Science & Justice argues this isn't good enough: "Forensic Hair Morphology Comparison -- a dying art, or junk science?:
There has been debate in both the judicial and forensic fields concerning the admissibility and reliability of the so-called forensic comparison sciences such as handwriting, tool mark analyses, and hair analysis. In particular, there has been increasing controversy over the use and interpretation of hair comparison evidence and it has been held partly responsible for miscarriages of justice.
Etc. etc. (Follow the link for the full article.)

So, is forensic hair comparison a dying art or junk science? Both, it would seem. Take, for example, this 2017 case study by Colin Campbell Ross and James Driskell titled "Is Microscopic Hair Comparison a Legitimate Science?":
There have been several wrongful convictions caused, at least in part, by flawed or exaggerated microscopic hair comparison expert testimony. In the US, the FBI has been under fire because testifying agents have overstated the value of hair evidence. In some instances, hair analyses that were correctly conducted and accurately reported to courts and juries have resulted in the convictions of innocent defendants.
Please, for heaven's sake, no more wrongful convictions.

But wait, forensics just may be proceeding apace, via hair proteins. The article Hair Proteins Under the Microscope, by Seth Augenstein, shows an emerging science for establishing distinctive identities, even among identical siblings, by analyzing hair proteins. If that doesn't blow our hair sideways, what will?