A new breed of police chase crooks down the information superhighway, reports Phil Reeves in Los Angeles
Donnell Howard Hughes seems to have prepared carefully for his crime. For weeks Hughes, a paedophile, had conversed electronically with a 13-year-old boy called Martin, swapping stories and jokes on a computer "chatline". Then he put the proposit ion that turned him from a cyber-pest into a criminal predator: "Let's meet".

Hughes drove to the agreed rendezvous - a restaurant parking lot in California. He had brought with him a bag filled with condoms and sex aids and a deck of cards for playing strip poker. But when he stepped out of his car, he received an unpleasant surprise - "Martin" promptly snapped his wrists in handcuffs.

Hughes, a 51-year-old insurance broker, had tangled with Sergeant Jim McMahon, one of America's small but growing band of "cybercops" who patrol the shadier reaches of the Information Highway in an effort to root out crime.

Their beat - they work for the San Jose police department in the heart of California's Silicon Valley - covers virtually every aspect of the computer industry. The team is currently hunting two men who stole $1 million of computer equipment and sold muchof it at rock-bottom prices on the Internet's bulletin boards. But it also tracks down on-line credit card fraudsters, weeds out software thieves and snares pornographers and paedophiles like Hughes (who was eventually sentenced to five years' probation).

"We are always extremely busy," Sgt McMahon says, pointing out that this year his department has solved 290 crimes.

In some ways, despite the complexity of Sgt McMahon's field, there is little to separate the cyber-sleuth from any other American city cop.

Sgt McMahon learnt his computer skills on the job, after gaining degrees in political science and personnel management. Although some of the other officers feel his work is rather nerdy, it is not desk job - and he still wears a 9mm Smith & Wesson at hiship. "This is as violent a situation as any other criminal activity," he explains. "In my four years on the Hi-Tech Detail, I have been on crime scenes where we have faced AK-47s, Uzis, sawn off shotguns, AR-15s . . . you name it, we've seen it."

"Martin" is only one of the many assumed names he has used in his undercover work. Not long ago he seized $100,000 of stolen chips after posing as a fence who ran a small computer company.

The theft of technology from Silicon Valley companies can involve many millions of dollars, and is not confined to hardware. Several years ago, the unit nabbed a former Apple employee who was touting the stolen " source code" for its 7.5 operating systemto another company, Radius Corporation. Radius decided to forego the possible commercial benefits and tipped off the police.

Sgt McMahon estimates there are only around 1,000 people patrolling the back alleys of cyberspace in search of crime. About half of these are federal, state or local police officers; the remainder are private citizens, predominantly those in the private investigation business.

But as the frontiers of the electronic world roll back, it is become increasingly clear that more resources are needed. (The fact that McMahon's is the largest computer crime investigation unit in the United States, outside the FBI, is a measure of the Mickey Mouse scale of things).

This is why he supplements his team's efforts by running a public bulletin board called Crime Bytes, a dial-in service to which the public can report e-crime, read details of other offences, and eventually (when the technology is ready) download picturesof wanted criminals and missing people." I believe in community policing. If you have thousands of people living and working in an area, then you have thousands of sets of ears and eyes. All I am trying to do is use them."

Whether this will suffice remains to be seen; computer criminals seem to be proliferating at the same speed as the technology they exploit.

Time magazine, for example, reported that Michelle Slatalla and Josh Quittner, journalists who live in Long Island, New York, had recently received "an electronic mail bomb", describing it as "equivalent to dumping a truckload of garbage on a neighbour'sfront lawn". Their Internet mailbox had been bombarded by so many thousands of unsolicited pieces of e-mail that it shut down.

Moreover, hackers had apparently illegally accessed the telephone company computers and reprogrammed the couple's telephone to forward calls to an obscene recorded message. Curiously, the Internet messages were reportedly signed by the "Internet Liberation Front", and railed against "capitalist pig" corporations which had turned the Internet into "an overflowing cesspool of greed".

Sgt McMahon and his team sometimes investigate "vapourware" crimes - confidence tricks for which criminals create dummy companies, offer non-existent products for sale, take orders electronically and then re-divert the resulting funds to a bank.

"You can be just as damaged on the Internet or on public bulletin boards as you can when someone sticks a gun in your face," he says. "If someone takes $20,000 from you on the Internet, it is no different than someone stopping by your house and taking it." Like any decent cop, he is always looking for informants. "In fact," he says, "I'd be very happy if you would published my Internet address: sjpd@netcom.com."