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Topic: Even scientists fail to understand the importance of blind testing (Read 4037 times) previous topic - next topic
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Even scientists fail to understand the importance of blind testing

I heard this programme on Radio 4 over the weekend.

In summary, fingerprint analysis is usually done "sighted" - the examiners know whether the suspect has an alibi, previous convictions etc.

A study has shown that, in marginal cases, the expert's judgement of the fingerprints can be swayed by this extra information - i.e. if the known print belongs to someone with motive, opportunity, etc then the expert is more likely to say that it matches the print from the crime scene. In the study, when the exact same prints were compared but the examiners were told there was no motive, opportunity etc, they were less likely to report a match.

Yet some fingerprint examiners reject this finding, taking it as a slur against their profession, and refuse to perform blind testing of fingerprints.


I listened to this programme in amazement. These scientists were saying exactly the same things audiophools say when they deny the placebo effect. Except they weren't fools - just completely unaware of the absolute need for blind testing, and the subconscious bias we humans suffer from.

The programme is here for a week...
http://www.bbc.co.uk/iplayer/cy/episode/b0...ind_16_11_2010/

...and this is the summary...
Quote
Forensic Science, Psychology and Human Cognition: When the Oregon attorney, Brandon Mayfield, was arrested for the Madrid bombings six years ago, the FBI's fingerprint examiners claimed they were 100% sure that his fingerprints were on the bag containing detonators and explosives. But they were wrong. And this sensational error has drawn attention ever since, to the widely held, but erroneous belief, that fingerprint identification is infallible.
Cognitive psychologists and neuroscientists have challenged forensic science as a whole to raise its game; and acknowledge that errors in fingerprinting and other forensic disciplines are inevitable because of the architecture of cognition and the way our brains process information. Claudia Hammond talks to Dr Itiel Dror, cognitive neuroscientist, whose groundbreaking studies first drew attention to the fact that individual forensic examiners can be swayed by context and affected by bias. Jim Fraser, Professor of Forensic Science from the University of Strathclyde and the Forensic Science Regulator for England and Wales, Andrew Rennison, discuss the steps being taken to amend procedures and protocols.


Cheers,
David.

Even scientists fail to understand the importance of blind testing

Reply #1 –
Uhmm... by what definition is a fingerprint examiner a "scientist"?

Even scientists fail to understand the importance of blind testing

Reply #2 –
^what he said. I was gonna ask the same question. I didn't know they weren't completely replaced by computers though. I guess they missed bronze orientation day.

Even scientists fail to understand the importance of blind testing

Reply #3 –
I think that's why all these debates on Hydrogenaudio interest me so much. In any case, my time spent here does not reflect the time I spend with actual music listening. It's just a very insightful playground for battles over truth and truthiness in general. The same happens all over the world with all kind of topics. But the benefit of HA (compared to other topics and virtual places) is better moderation and the feasibility of reasonable TOS!

Even scientists fail to understand the importance of blind testing

Reply #4 –
This is a common problem in places where "expert understanding" is involved, and where the people do not have training in perception issues.

It's a problem in many things, including "eyewitness testamony", police testamony, etc.
-----
J. D. (jj) Johnston

Even scientists fail to understand the importance of blind testing

Reply #5 –
It's not very difficult to forge fingerprints, e.g. with silicon, so even with perfectly reliable fingerprint identification, there is not necessarily proof that a fingerprint has been left by the person who is supposed to be its owner.
Ironically one of the best defense systems against fingerprint fraud is putting personal data like fingerprints online, so that anyone has access to them. This renders fingerprints practically useless in most forensic cases.

Even scientists fail to understand the importance of blind testing

Reply #6 –
Defense calls Arnold as expert witness on the police's methods.

The people calls your local hi-fi pusher.