Technology used by the US military to trace snipers in Iraq and Afghanistan is to be employed by British police to combat gun crime and terrorism.

The ShotSpotter system, already used by police in 29 cities across the US, uses patented technology to detect the exact location of gunfire or explosives within 80ft in less than seven seconds. It works by using an elaborate network of microphones placed on lamp posts, rooftops, masts and pylons in urban crime hotspots.

Four British forces are interested in using the technology to combat organised crime and gang violence: Greater Manchester, Merseyside, West Midlands and the Metropolitan Police. It will be trialled in the UK in September and in use six months later.

The sensors, grouped between 15 and 20 per square mile, recognise the sound of gunfire or mortar. Within five to seven seconds of a shot or explosion, they send signals to each other via GPS (global positioning system), locating the source through "acoustic triangulation". Less than a second later, a parallel video system can zoom in on the same spot, potentially identifying any criminals. Within 15 seconds of the shot, a detailed message is sent to police operators.

A spokesman for Merseyside Police commented: "This technology is a potential asset in the fight against gun crime. By notifying police as soon as a shot is fired, it could save invaluable time in reaching a crime scene."

The company behind the technology, ShotSpotter Incorporated, says that as well as expressions of interest from the UK police forces, it has spoken to the British intelligence agencies.

The technology was developed in 1994 to detect sniper fire in war zones. It is now used in New York, Chicago, Boston, Los Angeles, San Francisco, New Orleans, Philadelphia and Washington, DC. In Washington it already covers 17 square miles, and by next year will be expanded to cover the whole city.

ShotSpotter came to public attention in 1999 when it helped to catch a sniper who was shooting at drivers on a highway in Columbus, Ohio. The gunman killed one woman and was later jailed for life.

"American police have mostly used this for area protection and to accompany visiting dignitaries," said Gregg Rowland, senior vice-president of ShotSpotter Inc. "Part of its use is as a deterrent – when criminals know they can be heard and found, they are more likely to think twice before using firearms. Twenty-nine different police forces ... wouldn't put their faith in technology that didn't work." He claims that the technology has brought reductions in gun crime of up to 35 per cent.

Whereas US police officers carry firearms, many British officers do not. That means that when armed police in Britain are called to a scene where they are not needed, a scarce resource can sometimes be wasted. "There will be advantages to British police knowing for sure where a gun or explosion has gone off," said Mr Rowland. "And the concerns over civil liberties that are associated with CCTV don't affect ShotSpotter, because it only detects a certain level of noise, not normal conversation."

A British firm, Gun Shot Locating Ltd, has been founded to promote the technology in the EU. The company has held four demonstrations to British civil and military police, British intelligence agencies and police from Ireland and Denmark, in the north of England on 8-9 July and in the south on 21-22 July.

One of the four forces to have expressed an interest, whose identity remains confidential, is believed to have agreed to buy ShotSpotter in September.

Belfast Telegraph