The Metropolitan Police's x-ray weapons scanner is having an outing this week as part of the Operation Blunt knife crime initiative. A scanner has also been deployed to operate on passengers at Hammersmith bus station, but this one is not a Rapiscan 1000 x-ray unit - which is significant.

According to an eye-witness account published at Spy Blog, the Hammersmith unit ("Two metal poles with boxes mounted on them, with red and white flashing lights") is a heavily detuned conventional metal detector sited at one escalator, with no other exit covered. At a busy interchange a detector can't realistically be set to actually detect much, given that it will be set off by keys, mobile phones, money, all the bits and pieces you have to put in the tray before you walk through the detector at the airport. It has got to be, as Spy Blog says, "security theatre."

The Hammersmith scanner clearly has an effect in terms of profile and getting people used to the idea of being scanned, and might have had some impact before word got around. Luckless tooled-up youths walking through it could be searched, tooled-up youths obviously walking around it could be searched too, but in operation it would really only be a pretext to stop and search suspicious-looking youth, rather than a genuine deployment of weapons-detection equipment. It is not clear what powers are being used by the police for these procedures, but it might be possible to use section 60 of the 1994 Public Order Act, which does not require reasonable suspicion that an individual may be carrying offensive weapons, but which can be deployed in response to "a major increase in robberies at knife-point in a small area; or reports that individuals are regularly carrying weapons in a particular area" (Home Office guidance July 2004). Is that stretching it? Guidelines currently require that details of the search be recorded by the officer responsible, while new rules coming into effect in April will also require the stop to be recorded.

But even without the stop and search such a deployment requires the presence of officers, at the very least to make sure nobody steals the detector. Which makes it even more of an exercise in being seen to be tackling knife crime. The deployment is described as a pilot, for this week only, and the overall exercise is taking place in Hammersmith, Sutton and Southwark, with a rollout to the rest of of London planned in the future. A rollout of what is not entirely clear.

What about the x-ray machines? The Rapiscan, which is a cubicle affair (which takes your clothes off, yes we know) is even less appropriate for a high throughput security checkpoint than a conventional metal detector. And as it is a mobile unit, putting it in a fixed location for any length of time is a bit silly. So you can't put it in busy places, there's a limit to how frequently you can use it to say, cordon a pub and search everybody inside, and responding to knife crime by using it to search everybody in a shopping centre isn't likely to prove totally popular. Skip privacy and civil liberties, people - what imbecile bought this useless piece of gear in the first place?

Well, an upside is that the Met at least appears not have paid for it. The current operations are described by the Metropolitan Police Authority, here, where among other thing it tells us "The X ray machine is supplied at no cost." It's at least conceivable that the Home Office's stocks, which have been offered on loan to other forces, are all evaluation samples, but that still wouldn't provide adequate justification for the costs associated with the deployment of the devices.

The MPA document, which describes Operation Blunt as "initiative to deter young people from carrying knives on the streets of London", makes it pretty clear that it's consciously a marketing operation, as opposed to one that can be expected to produce many actual arrests. It notes that the initiative "affects this section of the community to a greater extent than the general population" ("this" being young people, but more likely young black people) and therefore: "To mitigate this there are specific activities in this initiative to engage and consult with young people, so that they can inform us on what would deter them from carrying knives."

The x ray machine will therefore be taken to "key public events for demonstration purposes to illustrate to young people the technology available for detecting the carrying of knives. It will provide an opportunity for the exhibitors of this equipment to discuss with young people the reason why knives are so prevalent and what could be done to prevent them being carried."

So, impressively, there's a conventional metal detector at Hammersmith operating under conditions where it can't rationally detect much useful, and a more sophisticated x ray scanner which is largely inappropriate for live deployments being used as part of a marketing campaign to show young people what the technology can do (except it can't really), and to engage them in discussion about knife crime.

It's psyops, but actually down there underneath the huge pile of techno-flummery you can see the Met starting to arrive at our best shot at an answer. It isn't possible to stop people carrying knives by detecting all the knives and confiscating them, and even if you (accompanied by choruses of 'What have you got to hide?') soften up the public to accept selective area stop and searches, you're still only running a marketing campaign. Actually getting people to stop carrying weapons is a much more complex task involving, among many other factors, engagement and persuasion. That's a tough one, and not something the Met can do on its own, but as the tech-based approach clearly can't work at all, it's better than the alternative. But couldn't we maybe just drop the technology nonsense, skip the tough talking about sentencing from the Home Office and cut straight to the point, in future? ®

Related links:

BBC news report
Clarke's x-ray specs - police swoops, detectors for schools
Home Office stalls on weapons scanner health risks
'See through clothes' scanner gets outing at Heathrow