Even though they are often used as restraining devices on members of the public, police do not carry out routine tests on Taser guns, a CTV News investigation has found.

It means that police officers are unaware of the true electrical output of what has proven to be a lethal weapon. 

This information has come to light in the wake of the death  in 2004 of Robert Bagnell, who was killed almost instantly after being shocked by a Vancouver police Taser.

Questions about the safety of Tasers have also been sparked by the recent death of Robert Dziekanski at Vancouver International Airport last fall. The polish immigrant is one of 20 Canadians who have died after being shocked by a Taser gun.

Engineering firm Intertek tested the two weapons fired during the Bagnell incident. Their research found while one Taser performed within a normal electrical output, the other was 30 times higher.

Taser International, a U.S. stun gun manufacturer, later disputed Intertek's test results. Since then, the two Bagnell Tasers were sent to the Canadian Police Research Centre in Ottawa for further examination. That was two years ago.

Victoria Const. Mike Massine, considered one of Canada's foremost police experts on stun guns, says Tasers are not tested by police.

"I'm assuming (Tasers) are tested at the factory," he said. "We don't have the mechanism to do that."

Professor William Dunford of UBC's electrical engineering department was surprised to learn that police don't regularly check their Tasers.

"It's reasonable that testing be done once a month or once a week, whatever is appropriate," Dunford said. "You look at how these things fail -- that's the whole engineering method."

Intertek's data came as a surprise to Federal Lliberal Party safety critic Ujjal Dosanjh.

"If they've known about this and have done nothing -- that is absolutely wrong," Dosanjh said.

Ten years ago, Const. Massine took part in Canada's first Taser trial. The six-month study set the stage for the purchase of the weapons by police forces coast to coast.

"How safe are they? It really depends on who you talk to," Massine told CTV News. "If you have pro-Taser people, they'll say they're safe. If you have anti-Taser people, they're gonna say they aren't safe."

With a report from CTV British Columbia's Peter Grainger