A 2009 report by a committee of the National Academy of Sciences found “serious problems” with an assortment of methods routinely relied on by prosecutors and the police, reported the New York Times. They included fingerprinting, blood typing, weapons identification, shoe print comparisons, handwriting, bite marks and — yes — hair testing. DNA was the game changer. The 2009 report said that, with the exception of nuclear DNA analysis, “no forensic method has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source.”
The Times produced a video documentary on the discrediting forensic evidence with DNA.
The Innocence Project, a nonprofit group based in New York that uses DNA testing to help clear people wrongly convicted of crimes, has played a notable role in casting doubt on how forensic science is applied. Nationwide over the past 25 years, the project says, 316 people sent to prison have been exonerated through DNA analysis; 18 of them served time on death row. Hair comparisons performed by crime labs were factors in nearly one-fourth of those cases.
This is not to say that these techniques are no good at all. Indeed, the F.B.I. still affirms its faith in microscopic hair analysis, particularly as a first look. But it now tries to follow that procedure with a deeper and more certain investigation that uses DNA sampling, and it has done so for 18 years. Nonetheless, many forensic methods no longer come wrapped in the shield of invincibility they once widely enjoyed (especially among those prone to take TV shows literally). Fingerprints get blurred, bullets get smashed, blood specimens get tainted, hairs get mischaracterized.
In addition, the F.B.I. says it is examining more than 2,500 old cases that lacked DNA evidence, to determine if hair analysis, of itself, played a role in guilty verdicts. It is unclear how far along this review is.
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