This entry was posted by Friday, 15 October, 2010
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No two people have the same fingerprints.

That’s how come we get to put people in jail or stick ’em in the lectric chair based on fingerprint evidence. It’s “incontrovertible”

How DO we know that fingerprints are unique? That no two people have the same ones?

Well.. see.. that’s the thing.

Experts such as Simon Cole (New York Times) say its’ a lot of hooey. It’s just “folk wisdom”. Fingerprint matching, says Cole, isn’t nearly as reliable as we grew up thinking it was.

How many whodunits have you read where the bad guy left prints on the wine glass? If they matched, he’s catched.


You’ve always accepted that this was completely true. You don’t want to get into an argument with your own brain, do you?


from an article in Wikipedia about fingerprints:

“Despite the absence of objective standards, scientific validation, and adequate statistical studies, a natural question to ask is how well fingerprint examiners actually perform. Proficiency tests do not validate a procedure per se, but they can provide some insight into error rates. In 1995, the Collaborative Testing Service (CTS) administered a proficiency test that, for the first time, was “designed, assembled, and reviewed” by the International Association for Identification (IAI).The results were disappointing. Four suspect cards with prints of all ten fingers were provided together with seven latents. Of 156 people taking the test, only 68 (44%) correctly classified all seven latents. Overall, the tests contained a total of 48 incorrect identifications. David Grieve, the editor of the Journal of Forensic Identification, describes the reaction of the forensic community to the results of the CTS test as ranging from “shock to disbelief,”..

Not so good, eh? Get yourself a mediocre fingerprint technician and who KNOWS what fate has in store. (Latents, by the way, are prints that don’t show up till you “dust em”).


Maybe there’s a better way.

Dr. Mark Nixon (and others) at the University of Southampton say that  the little swirly thing in the ear,  the helix, is durn good for telling us apart with close to 100% accuracy. That’s what we’re looking for, right? 99+ %?  Will “earprints” replace fingerprints at Scotland Yard?

Not likely, according to A Wild at the University of Rhode Island (That’s as much identification as your gonna get; he’s one of Mister ScienceAintSoBad’s best kept secrets). Wild reminds us that accuracy isn’t enough. Criminal types, he says, would have to start scattering photos of their own ears around crime scenes or, perhaps, begin pressing the sides of their heads against corpses, for ear detection to have any forensic value. Whereas it is hard to avoid leaving fingerprints and DNA behind, your average perpetrator can probably figure out how to keep his ears off the walls.


To be fair, Dr. Nixon and his colleagues probably had different applications in mind for the ear identification technique such as biometric screening. For that purpose, with further development, it may well turn out to be useful.


Photo Credit: FBI (Thanks, guys.)


  1. Quora

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