The Musings of Harry

Harry was among the recipients of Blair’s email sent to signatories of the Downing Street anti-id card petition. The entire email is nonsense: for the most part its arguments are the same old hat. The Government’s claims about terrorism, immigration, passport regulations, cost and soforth have been discredited on many occasions and there’s no particular need to repeat those arguments here. One paragraph, however, caught my eye — and several other people’s:

I also believe that the National Identity Register will help police bring those guilty of serious crimes to justice. They will be able, for example, to compare the fingerprints found at the scene of some 900,000 unsolved crimes against the information held on the register.

This is the first time that the Government have made this argument (they’re contradicting themselves, again, by the way). It’s also one of the things that this Government seems to misunderstand. This kind of idea is one of the most scary prospects raised by the increasing ubiquitousness of mass surviellence, it is dangerous, and is a threat to all of us. Why, you may say? What’s wrong with catching more criminals? If you’ve committed no crime, you’ve got nothing to worry about, right?

Wrong.

The massive, dangerous, incompetent gap in the Government’s thinking is to assume that fingerprints as a means of identification are 100% accurate, when in fact, they are not. This is not hard to see, even without knowing the details: nothing is infallible, and to predicate a policy on anything being infallible is really quite stupid. As it turns out, in this case, we do have details. We do know that fingerprints are not always reliable. One study, published in the Journal of Criminal Law & Criminology, placed the error rate at anything between 0.8% and 4.4%. From these figures, some simple maths shows fairly clearly why these fishing expeditions on big data sets are a really bad idea.

Blair said that unknown fingerprints from 900,000 crime scenes could be matched against the database. He’s actually not being honest: we know that this figure refers to the number of “crime scene marks” rather than the number of crime scenes. Therefore, we can assume that 900,000 is the total number of fingerprints to be checked against the NIR. The research above gives us a range of possible error rates: that is, the percentage of fingerprints that will give a positive match when in fact, the fingerprints are from different people. Let’s be conservative again, and take the lower figure of 0.8%. 0.8% of 900,000 is 7,200.

That means, if these figures are correct, that 7,200 fingerprints would be incorrectly matched, and would incorrectly place their owners at the scene of a crime. Even if you doubt the figures, the principle still stands: reduce that number by half and you still have a significant problem. If the upper figure of 4.4% were correct, we’d be talking about more than 39,000 false positives.

One could of course dive into a paranoid diatribe about huge miscarriages of justice that would occur as a result, but Harry believes that the reality would be somewhat more mundane: the police would have to investigate all of these people (in addition, obviously, to those correctly matched) to determine the quality of the evidence against them. This, of course, would be a massive waste of time and money. It’s doubtful that the police would consider doing this even were they asked to: they are streched thin enough as it is.

It’s this kind of slipshod thinking that makes the Government’s legislative agenda really worrying. It’s really very unlikely that the Government is full of morons who don’t realise that these problems exist. This leads one to question their motives. They’re either trying to sell the scheme on policies which they know to be infeasible, in which case they’re full of shit, or they haven’t thought these ideas through before presenting them, in which case they’re incompetent, or they’re up to something. Decide for yourself which you believe.

Harry will be voting tactically at the next election, with the sole purpose of ejecting these cretins from power.

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This entry was posted on Tuesday, February 20th, 2007 at 14:13 and is filed under Identity Cards. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.