Wednesday, November 22, 2006

The 60% Problem

The big story this morning, at least in this part of the world (NW England), was that the local police are being issued with fingerprint checking devices. Reporters and civil libertarians alike reported breathlessly about the police's new ability to carry out roadside checks to check identities. Some seemingly conflicting assertions and figures were bandied around on TV and on the web: - 60% of people stopped by the police give false identity information - The automatic number plate recognition (ANPR) teams, who already cross check vehicle number plates against databases, will be able to verify a person's identity within five minutes without having to take them to a police station - More than 6.5 million fingerprints are cross-referenced - The device has an accuracy of 94-95% and will be used for identification purposes only, say police, and there are electronic safeguards to prevent misuse - The encounter can be 15 minutes on the roadside rather than three hours in the police station - Fingerprints will only be stored onto a mobile device until it is full, which is at around 100 fingerprints. - Inspector Steve Rawlings said it takes two sets of fingerprints and the fingerprints are not retained - The device could save police forces £2.2m a year in resources wasted pursuing false identities So let's get this right: The police stop someone driving a car, perhaps acting suspiciously. They run the number plate and find out who the person driving it should be, based on insurance or registration information (or both). If the car doesn't have insurance, they arrest them and take them to the police station for driving without cover. They can find out who they are later I imagine. They ask the person who they are; if the details provided don't match the owner listed on their system, or the person isn't able to name that person and explain why they're driving the car, their fingerprints are taken. The fingerprints are checked against a database that contains about 10% of the UK population's records. There are something like 38 million drivers so we could be generous and say that if everyone who has committed an offence is also a driver, then something like 15% of the population is in the fingerprint database. If they're not in the fingerprint database, we have to trust they are who they say they are and either take them to the police station to find out more or let them go. But 60% of people who are stopped apparently provide false information. That's a stunning figure. The assumption must be, I suppose, that 6 out 10 are guilty of something and so tell lies about who they are, risking the police taking further steps. The next assumption must be that if you're prepared to tell a lie to the police, you're more than likely to have committed an offence for which you were fingerprinted and so you have your record on file and it will show up. The missing figure is perhaps how many people are stopped per year so that I could compare the 60% false identity giving with the 6.5 million records in the national fingerprint database and the £2.2 million cost of followup. Further, rather than delete records right away, the police want to hang on to "100" (or until the machine is full - must be ZX81 style memory), hoping that they'll catch you again and fingerprint you with the same machine. I can see these statistics being trotted out again, pretty soon I suspect, to justify ID cards and fingerprints being stored upon verification for later checking. All for £2.2 million in follow up costs by the police forces? I think I'm more interested in what the 60% are up to giving false identity data and whether more bad folks will be put away.


  1. Anonymous10:54 pm

    You've got no argument with me on this post. I noted an amazing lack of value judgement, it was quite an apolitical observation.

    I'd keep the fingerprints as a matter of course, which of course is a hope. No resource investigator could possibly miss this potential. It's the physical equivalent to recording the telephone number of people who ring you. One may not know whose hand this is, you've just fingerprinted, but we know it's the same hand as someone who lied to us last time. This is incredibly useful information, that may not be kept by the police but I'd be shocked if it wasn't recorded by somebody.

    However since most of my childhood mates were criminals, murderers, and the generally undesirable and almost all my adult mates are in law enforcement, or thereabouts, I don't particularly subscribe to the Socialist worker/Grauniad mentality that "Coppers are all fascists, especially as Ian Blair's got himself so well covered with his tapes of his conversations with the Attorney General et al, he can afford to actually enforce the law, as can be seen by the at least ostensibly genuine money for peerages scandal.

    It also has a huge potential piece of help for someone else, whom I'm sure have also worked out the possibilities of using their friendship with the public face of the law, for bypassing biometrics.


  2. Anonymous3:23 am

    One thing though, they now have 100 fingerprints of folks whose cars match their insurance and indentification. So you could perhaps say, this is a way of getting that 10% number up a bit?

  3. Even if they have the 100 fingerprints in the machine, I guess they're not authenticated to a standard that would allow them to be stored in the main database.

    This whole thing rests on a statistic that wasn't published, i.e. that someone stopped for one offence is more likely than not to have other offences outstanding, hence why 60% give false details (they know, of course, that they're wanted for something else or that they might be and so try and evade capture by giving false details). I'd love to know what that stat is.