Before disaster strikes

A system that can detect concealed weapons in a crowd without alerting suspects that they have been spotted is at an advanced stage of development in the US.

The US government plans to combine millimetre wave (MMW) sensor technology with new image processing software to give security staff at airports, courthouses and other public buildings advance warning of people carrying guns, knives and other hidden weapons.

Details of the ambitious project , led by a UK researcher, were confirmed by a US security source, who said the system could be ready for full-scale trials by the end of next year.

It aims to reduce the risk of incidents such as the one at Los Angeles airport in July, when a man walked into the terminal armed with two pistols and a knife. He shot two people dead at the ticket counter of Israeli airline El Al before being killed by security guards.

MMW detectors monitor the difference between natural heat energy emitted from the human body and solid objects carried about the person. The variations are represented as an image, revealing shapes such as guns and knives.Unlike X-ray scanners, passive MMW systems emit no radiation and have no immediate health implications. They can also reveal both metallic and non-metallic objects.

The US Department of Justice has sponsored California-based Trex Enterprises to develop a compact, portable MMW weapons detector. It wants one small enough to be built into walls or otherwise concealed and affordable enough to go into widespread use.

The project is being led by Trex Enterprises’ UK researcher Dr Stuart Clark, who said a working version should be ready before the end of the year.

‘We are about three months away,’ said Clark. ‘We’re assembling and refining parts of the system on a daily basis.’

He added: ‘We have the physics working and I have a high degree of confidence in the technology. The challenge has been to build these portable, affordable systems.’The authorities plan to combine the MMW detector with advanced image analysis software being developed separately at the US Air Force research laboratory in New York State. The software would process data from the MMW sensors, looking out for suspicious objects and alerting security staff when necessary.

The development of a software processing layer that sits between the MMW images and human operators is crucial to the success of the system on several grounds, according to the US security source.

It takes human guards away from the scene of potential danger. Security checks using MMW and other advanced screening technologies have been tested at airports around the world since September 11 last year, but always in the form of a distinct portal where people know they are being screened and can react if they think they have been discovered.

A covert system using image processing software could also continuously monitor crowds far more effectively than a human being struggling to maintain concentration.The system’s developers hope automated processing would also remove some of the invasion of privacy issues inevitably raised by MMW imaging, which left to its own devices visually undresses a human being to the bare skin.

The software would reveal only solid shapes, representing the rest of the body as an indistinct mass.

The US authorities envisage the MMW weapons scanner taking its place alongside a range of new sensors that will be used both openly and covertly in high-risk public buildings within the next few years.