San Francisco - Ten years ago, two teenaged misfits walked into their high school in Columbine, Colorado, and proceeded to perpetrate one of the most horrific mass murders in US history.

Eric Harris and Dylan Klebold were both 18 when they launched their attack on April 20, 1999, wielding sawed-off shotguns, a semiautomatic pistol and home-made bombs.

For 49 minutes they rampaged through the building as America watched on live TV, killing 12 students and a teacher and wounding 24 others before committing suicide.

The initial theories that they were reacting to bullying at the school have since been debunked. While no firm motive has emerged for their atrocity, the notion that they were ordinary kids who strayed has been debunked by most psychologists who have studied the case.

"These are kids with serious psychological problems," says Peter Langman, author of Why Kids Kill: Inside the Minds of School Shooters. "These are not ordinary kids who played too many video games. These are not ordinary kids who just wanted to be famous. These are simply not ordinary kids."

In the aftermath of the killing, the overriding sentiment of "never again" promised to cast a new focus on America's lax gun laws. But the hopes of anti-gun activists were sorely disappointed, says Daniel Vice, senior attorney for the Brady Campaign, a national organization that lobbies for stricter gun controls. The group was founded by Ronald Reagan's White House press secretary, who was paralyzed during the assassination attempt against the US president in 1981.

"At the state level, things have changed for the better, but not at the federal level," says Vice. "In fact, under President George W Bush they moved backwards. He was listening to the gun lobby. They had bragged they would be operating out of the White House, and under Bush they were."

Some examples: Bush failed to renew a measure requiring a five-day waiting period for the purchase of handguns or a federal ban on military-style assault weapons.

Vice is hopeful that under President Barack Obama the tide can be turned. But anti-gun activists have looked on with horror in recent months at a surge of high-profile violence - mass murderers using guns to go on the rampage in California, Alabama, New York, Washington and elsewhere, claiming almost 60 lives in less than a month.

"It's still very easy for dangerous people to get dangerous weapons," Vice says.

That recent spate of mass murders should increase the clamour for tighter gun control. However, a recent CNN poll found just 39 per cent of Americans in favour of stricter laws, compared to 54 per cent eight years ago.

How easy is it to get guns in America? In one recent investigation by ABC's 20/20 programme, the brother of one of the 32 victims of the 2007 Virginia Tech massacre was given 5,000 dollars in cash to go to a gun show. He bought a Glock handgun as he was waiting in line to get in.

Within an hour, he proceeded to fill his car with a veritable arsenal - no background checks, no questions asked, and no record of where those guns go next.

That ease of acquisition not only spreads death in the US - it exports it to the country's neighbours.

"Military-style weapons are flowing across the border to Mexico," says Vice.

The US neighbour to the south saw more than 6,300 people slain last year in drug-gang wars.

America's culpability was noted by Secretary of State Hillary Clinton on a recent visit to Mexico.

"Our inability to prevent weapons from being illegally smuggled across the border to arm these criminals causes the death of police officers, soldiers and civilians," Clinton said. "I feel very strongly we have a co-responsibility."

That sense of commitment gives Vice hope after a decade in which initial promises to tighten gun controls were flouted.

"The gun lobby lost big in the last election," he says. "We are hopeful that with the new president and Congress things will finally start to change."

But the facts on the ground may be more stubborn. A study by the FBI found that gun sales in the first three months of 2009 are up 27 per cent over the prior year - perhaps because gun lovers fear a weapons ban, or are more worried about public safety as the economy worsens.