News analysis: Deadly games - They're bloody. But can they make you a killer?

Gareth is a professional killer. He'll shoot you down in seconds, then finish the job with the razor on his sleeve. And he won't just get away with it - he'll be paid handsomely, and cheered on by thousands of people.

The slaughters happen in Asia. There, this clean-cut, cold-eyed 21-year-old from the West Midlands challenges all-comers and murders them mercilessly, under blazing stage lights in vast arenas. "The one who eliminates his opponent the most times wins," says Gareth Marshall, a full-time electronic gunslinger.

He is among the Top 10 computer duellists in the world. To guarantee a life of free flights, hotels, sponsorship and non-stop destruction, he practises the game Quake for up to 12 hours a day. So does he ever emerge, blinking into daylight with the urge to slash his way through the queue at the Walsall Sainsbury's? "No," says Gareth flatly. "Why would I?"

Because violent video games turn nice young men into real-life killers, if you believe the critics. Manhunt, in which you choke, strangle, stab and shoot your way out of a nightmare city, was blamed for the murder of a boy in Leicester. The teenage killers of Columbine High in the US were hard-core players of the hellish game Doom. And as reports came in of Cho Seung-Hui's deadly rampage at Virginia Tech on Monday it was assumed he must also have been under the influence of some gruesome shoot-'em-up.

But then we saw scenes of him appearing to emulate the murderous South Korean movie Oldboy. It was film that got the campus killer going, it seems - which chimed eerily with the findings of the British Board of Film Classification (BBFC), published a day after the shootings.

"Some research in the US appears to support the hypothesis that playing video games can make people more aggressive," says the BBFC, whose job it is to evaluate and certify the goriest. But while players may lose track of time and become "zombie-like" after hours in a fantasy world, the BBFC believes they are unlikely to want to kill anyone for real.

Games just do not generate the same level of emotional attachment as films, the report says. Cinema-goers often forget they are watching a screen and feel such empathy for characters that they weep. That rarely happens in front of a PlayStation, says the BBFC. "Intense concentration, and fierce determination to win or make progress, are not the same as deep emotional involvement [in the story]."

Even the most absorbed players remain aware of guiding the action, which makes them less likely to confuse games with reality. It also allows them to do things they wouldn't even watch on film. "My brother was playing it once and he was in a car with a prostitute," a gamer from Newcastle told the BBFC. "He was only about nine or 10. If it was in a film, it's dirty - but in a computer it's funny."

The boy was probably playing Grand Theft Auto (GTA). This series, which has sold 35 million copies, was developed by a design team in Edinburgh called Rockstar North, responsible for some of the most notorious games around.

Adult titles are booming as the target audience ages: two-thirds of gamers are now adults. Your correspondent is among them, having once bunked off college to play a football management simulator for three days. Staying up all night to test the effects of hack, slash and shoot games sounded awful, and yet ... within an hour of firing up GTA, I was stealing police motorcycles, ploughing through pedestrians and punching people in the street just for fun, like a happy slapper in a hoodie. And laughing out loud, as an alarmed friend pointed out. "Players become involved in actions that are absurdly remote from their everyday life and this absurdity makes them laugh," says the BBFC. In a traffic jam next morning I had a very powerful urge to ram my way through and steam off down the wrong side of the road.

The scenes from GTA replaying manically in my brain were mixed with others from World of Warcraft, a virtual universe with more than eight million online players. Some call it Warcrack, it's so addictive. "This one's a life-stealer," said the young man who sold it to me. "You team up with people who are in Romania or somewhere, hours ahead. Quit and they lose points, so you stay up. They go to bed at two, but for you it's four. And you've got to get up for work at seven."

Warcraft takes a mind-numbingly long time to create an avatar and develop skills. Hacking wolves to pieces got boring, so I reached at last for Manhunt, said to be the most violent game around. Several shops refused to sell it after Manhunt was linked to the death in 2004 of 14-year-old Stefan Pakeerah, stabbed and beaten to death with a claw hammer after being lured to a park by a friend.

Sales soared when its influence was reported, although the judge, lawyers and police said Manhunt played no part in the crime. In it, you are James Earl Cash, a murderer taken from Death Row by the unseen director of a slash movie, who will only let you go if you kill hoodlums as graphically as possible. So you pull a plastic bag over one man's head and hold him down while he struggles. Eventually, you get a chainsaw.

It looks like a horror film, and the sequel this summer will be even more vivid. Games are expected to become more realistic and therefore more involving, because developers long to make us cry like we do at the movies. When that happens (if you follow the BBFC logic), they will get more dangerous. Giselle Pakeerah, Stefan's mother, still blames Manhunt for her son's death. She says the release of a sequel "shows how morally irresponsible the industry is".

Edgy, exhausted, with a headache and burning eyes, I quit Manhunt as dawn came, understanding why the follow-up will be rated 18-plus. Even Gareth Marshall, full-time virtual gunman, thinks it is sick. But he insists - like so many in the industry - that games do not make killers.

"There is always other stuff going on in the lives of these people," said the mild-mannered young assassin. "Anyway, who is giving them the games? I know parents who say Grand Theft Auto is doing terrible things to their little boy, but it's an 18 and they're letting an 11-year-old play it. Who do you think is to blame there, then?"

World of Warcraft

8.5 million subscribers

Vast, online, multi-player fantasy world. Create an avatar to take on beasts, monsters, orcs and wizards in an ever-expanding, obsessively detailed universe.

A board game long before 'Lord of the Rings' movies. Virtual version by Blizzard Entertainment, California.

UK rating: 12-plus

Gory, but requires endless patience to acquire weapons and skills.

Medal of Honor

27 million sales

Fight them on the beaches of Normandy in the most successful Second World War simulation of all. From an idea by Steven Spielberg whilst making 'Band of Brothers'. Developed by the LA studio of games super-power Electronic Arts.

UK rating: 16-plus.

Achtung, eat lead! Realistic soldiers spray bullets on historic battlefields, but die comic-book deaths.

Grand Theft Auto: Vice City Stories

13 million sales

Drag out a driver, steal a car, pick up a hooker and build a criminal empire in 1984 Miam (with cheesy soundtrack).

Created on the mean streets of Edinburgh, Scotland, by Rockstar North, a software team founded in the Eighties.

UK rating: 18

Sleazy, easy violence but the graphics are cartoony and the blood glows like radioactive ketchup.

Manhunt

Fewer than 1 million (estimated)

Slaughter your way out of an urban nightmare using anything from a plastic bag to a chainsaw. Meet the Smileys, who love to dismember.

The most notorious game on the shelves is another one by Rockstar, now owned by US company Take-Two Interactive. A sequel is due out this summer.

UK rating: 18

Looks like a slasher movie, with killing the only aim. Vicious. Nasty. Deranged.