http://www.economist.com/blogs/babbage/2012/02/surveillance-technology
Surveillance technology
Transparency above all
Feb 3rd 2012, 13:10 by C.F. | BONN
SECURITY types and privacy watchdogs rarely agree on anything. They do, however, both concede the importance of transparency. The rub is that whereas for human-rights advocates this means no underhand shenanigans impinging on citizens' civil liberties, security experts think of the ability literally to see through people and detect whether they are carrying any potentially threatening implements. The latest spat erupted in January when Raymond Kelly, New York's police commissioner, declared that his force is working with America's defence department to have so-called T-ray scanners mounted on squad cars. Mr Kelly said that the technology offers "a great deal of promise" in detecting concealed weapons without a physical search.Terahertz radiation, to give T-rays their less jazzy name, makes up a band of the electromagnetic spectrum squeezed in between microwaves and infrared, equivalent to frequencies of 300 billion-3 trillion cycles per second. Everything with a temperature of 10 degrees above absolute zero or more emits T-rays. What is more, different substances sport characteristic terahertz tags. Scientists have had some success in using T-rays to distinguish similar substances and hope one day to be able to tell, say, cancerous tissue from healthy one, or benign plastic from plastic explosives. Today's terahertz scanners are, however, clever enough to tell a human body, which emits copious amounts of the stuff, from, say, a metal handgun, which produces much less. And they can do this from a distance, without shining a beam on its target first, as is the case with X-rays.
Since 2004 ThruVision, a spin-out from the Rutherford Appleton Laboratory, a national research facility in Oxfordshire, has been building scanners which it claims can do just that. Three years ago the company rolled out a device the size of a big loudspeaker, called T5000, which it has since sold to the Dubai Mercantile Exchange and London's second financial centre, Canary Wharf, among others, where it aims to pick out biggish concealed objects non-invasively as far away as 25 metres. Last year it announcedthat the United States Air Force purchased an upgraded version of the T5000, the TS5, whose range stretches up to 30 meters for large objects.
Predictably, the idea has civil libertarians up in arms. The New York Civil Liberties Union, an advocacy group, told the New York Times that "the public needs more information about this technology, how it works and the dangers it presents." It may draw comfort from legal precedents. In 2001 the Supreme Court ruled that the police need a warrant to deploy a thermal-imaging systems to detect high-intensity lamps of the sort used to grow marijuana. Earlier this year it handed down a decision forbidding law enforcement agencies to track suspects using GPS without a judicial thumbs-up. Terahertz scanners will no doubt spur similar legal wrangles.
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