The myth of fingerprints

The Observer newspaper is reporting plans being made in the European Union to impose mandatory fingerprinting on all children in the EU down to 12 years old, and possibly even down to 6. This is part of the “biometric passport” system, but they are explicitly talking about retaining and sharing the data between countries and agencies. There’s even talk of allowing access to the intelligence agencies of non-EU countries.

Lest anyone say, “What’s the harm?” or “The innocent have nothing to fear”, I’ll say once more that this is only true if the system never makes a mistake. However, fingerprints are not infallible. Sure, everyone knows that everyone’s fingerprints are unique (although, interestingly, this has never been proved – it’s simply assumed to be true). But when we start to talk about taking fingerprints, it gets harder. A print isn’t a perfect representation of the finger (there are always splotches and gaps), and a crime-scene print is often smudged or partial. When it comes to matching imperfect prints against the similarly imperfect prints stored on a database, the assessment (which is done by a human being, with their own error rate) becomes subjective and dubious. One problem is that fingerprint matches are always given as “matches” – this is definitely the person you want. Everywhere else in scientific evidence, we talk about the probability of a match being chance (1 in a 250 000, 1 in 900 000 and so on). Why should fingerprints be treated specially? And if “they” are going to start matching crime-scene prints (or whatever) aganist a EU-wide database with hundreds of millions of prints in it, those error rates had better be very small indeed or hundreds of people will get convicted of crimes they didn’t commit. Don’t think that could happen? Check out this, this article and this article from New Scientist (some require a sub to read fully) for an idea of the debate going on in the scientific community about this technique.

Are you worried yet?

pax et bonum

Article posted at 08:52am on 30 July 2006
Category: Politics, Science, General