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Gallery: The Science of Forensics

In 2005, Congress asked the National Academy of Sciences to survey the landscape of forensic science. The result, this past February, was a 255-page report. Here are a few of the surprising facts they found.

By Matt Ransford Posted 3.26.09 at 3:28 pm 2 Comments

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Hair

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Television detectives relish pulling a single hair from a crime scene, like the proverbial needle from a haystack. "If only the perp hadn't shed this one strand," they say, "he would've gotten away with it." In real life, though, a strand of hair is not the smoking gun CSI may have you believe. While hair evidence may be valuable in narrowing a field of suspects, matching it to one particular individual is not at all a straightforward task. Forensic scientists use a variety of indicators--color, length, thickness, whether hair has been dyed or curled--to assign a hair to an individual, but there is no threshold for how many features must be the same in order to declare a match. Even when the examiners determine a match under a microscope, the potential for error is high. A 2002 FBI study discovered microscopic matches to be wrong 12.5% of the time when subsequently checked with mtDNA analysis.

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2 Comments

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rjgarrett

03/27/09 at 7:47 pm

This story relates information about a proficiency test allegedly conducted by the International Association for Identification in 1995. It also infers that the recently published NAS study references that study in their report. Both allusions are factually incorrect. The IAI has never conducted a proficiency study regarding fingerprint examiners. Collaborative Testing Services (CTS), did attempt to conduct such a test in 1995. The IAI was not a part of that study. From time to time we are contacted to recommend sources for information and guidance. While those involved who participate may be members of the IAI, they do so as independent agents not representing the IAI. The CTS test was problematic in that it was poorly designed, allowed participants who were not trained fingerprint examiners and used examiners from international venues who practice to a different standard. The results of that test were long ago dismissed as unscientific and not reflective of the fingerprint community. Please remove any reference to an IAI proficiency test in your article. You are free, from my perspective to identify CTS, but it would be dishonest to represent that test as a measure of the competency of fingerprint examiners in the US. Thank you.

Bob Garrett,CSCSA, CLPE, FFS
President
International Association for Identification

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ford2go

03/29/09 at 1:57 am

garrett is making a pretty strong call of bs. If he is who he says he is, it would seem that he's correct

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