There's a chap called Simon A Cole who's been calling into question the forensic validity of fingerprints.
Here's a link to one of his many papers, "
Is Fingerprint Identification Valid? Rhetorics of Reliability in Fingerprint Proponents' Discourse" from his, University of California, Irvine
webpage.
Part of his argument is something he calls the fingerprint examiner's fallacy.
"
The fingerprint examiner’s fallacy holds that the fundamental empirical
question concerning forensic fingerprint identification is not
How accurate are latent print examiners’ attributions of source?
but rather
Are all human friction ridge arrangements unique?"
At the heart of the fingerprint examiner's fallacy, therefore, is the elevation of
uniqueness over
accuracy.
Before going on, here are the compulsory links to
Brandon Mayfield (erroneously linked to the Madrid train bombings of 2004 on the basis of fingerprint evidence) and
Shirley McKie (accused of leaving her thumbprint at a murder scene). Both examples of cases where the fingerprint examiners got it spectacularly wrong: unfortunately I can't link to other cases where they got it spectacularly wrong until the people concerned prove their innocence.
However, it isn't only within the area of fingerprints that the fingerprint fallacy crops up.
In
Dallagher, a ninety-four year old, deaf, arthritic woman was suffocated while she was in bed. It seemed clear that an intruder had broken into her house through a small transom window above her bed during the middle of the night: he had scrambled through the window and then suffocated the victim. The prosecution made the case that the intruder was the appellant. Ear prints were found on glass immediately below the transom window; the prints were examined by experts and compared to control prints provided by the appellant and others. The experts found that the ear prints from the scene matched those provided by the appellant who was subsequently convicted.
Later however, the conviction was found not to be safe and was overturned.
While another case, as reported by the
BBC ('Ear print' burglar wins appeal), was overturned.
In this case the fingerprint examiner's fallacy was shown when "
... specialist ear-print officer Cheryl McGowan told the jury that no two ears were the same [(
uniqueness)]
and she did not believe the ear could belong to anyone other than the defendant [(over
accuracy)]."
Q. Err, Cheryl ... how accurate is your belief?
A. One-hundred Percent.
Q. Based on what?
A. ...
Anyway, here's a much subtler one from
Job v Halifax [2009]. In brief, a chap has phantom withdrawals taken from his bank. He complains to the bank; they don't reimburse him; he takes his complaints to the court.
Anyway, during the proceedings
Inglis J said,
"
It is said that it is for the bank to show that the card did not have any flaws that would enable the key to be extracted from it; that a strong random number generator was used; that there were appropriate controls on key management; and that there were appropriate controls on the personalisation process. The only evidence is identified as being Mr Baker's assertion that there has never been a key compromise in the industry. The assertion is only a statement of the bank's ignorance."
That, "
there has never been a key compromise in the industry" is the
uniqueness part of the fingerprint examiner's fallacy. Again, this is presented
in lieu of
accuracy.
What are the accuracy rates? It is implied that they're one-hundred percent but where's the evidence? How was it measured? Is your measurement process valid? Etc.
Mr Justice Inglis's comments are quite interesting here,
uniqueness in lieu of
accuracy ... "
a statement of ... ignorance."
As I read the Law Commission's consultation paper
Expert Evidence in Criminal Trials I wonder whether or not their recommendations will end up getting rid of fingerprint evidence. I doubt it. They only mention fingerprints once in the report and that is with regard to something called
judicial notice. This is where the judge says, "
it's obvious to me the technique is valid, I'm not prepared to listen to any arguments otherwise, so the evidence can be admitted."