OTTAWA - The RCMP has loosened a restriction on multiple Taser shocks amid growing evidence that repeated stun gun jolts increase risk of death.

A new statistical analysis by Montreal biomedical engineer Pierre Savard suggests the chances of someone dying after being hit with a police Taser increase the more times they are stunned.

The research comes as a public inquiry examines the death of Polish immigrant Robert Dziekanski, who got five shocks from an RCMP Taser in October 2007 at the Vancouver airport. An amateur video of Dziekanski writhing on the floor was beamed around the world, sparking new questions about stun gun safety.

Savard carried out the study using a database of over 3,200 RCMP Taser incidents from 2002 to 2007 compiled by The Canadian Press and the CBC/Radio-Canada. He also looked at an Amnesty International study of Taser cases involving more than 300 deaths in the United States.

During the six-year period, nine people died in Canada after being Tasered by the RCMP. In at least seven of the nine deaths, accounts indicate the person was jolted multiple times.

"What is new here is the high level of relationship between the duration and the risk of death," Savard told the CBC.

"So it is a linear relationship, the more you are exposed - if you double the exposure, you double the risk."

Taser International, the Arizona-based maker of the stun guns, has vigorously defended their safety - in and out of court. The manufacturer says no use-of-force tool is risk-free, but stresses that the weapon has not been directly responsible for a Taser-related death in Canada.

RCMP complaints commission chairman Paul Kennedy has called on the RCMP to restrict Taser use to major threats where a person is combative or risks serious harm to themselves or others.

The RCMP says it has limited Taser use to situations involving a threat to officer or public safety.

The electronic devices can be fired from a distance and cycled repeatedly once steel probes puncture a suspect's skin or clothing. The guns can also be used multiple times in up-close stun mode, a sensation likened to leaning on a hot stove. A typical cycle lasts five seconds but can be made to last longer.

The new RCMP policy warns officers that Taser use carries a risk of death, particularly for agitated people. And it still advises them that multiple or continuous shocks "may be hazardous to a subject."

However, the police force has scratched a warning first made in 2005: "Unless situational factors dictate otherwise, do not cycle the (Taser) repeatedly, or more than 15-20 seconds at a time against a subject."

Savard, who has submitted his findings for publication in a peer-reviewed science journal, said the the 15-to 20-second threshold is the point at which the chance of death can increase dramatically.

"When we see that risk of fatality increases with exposure it is a strong argument in favour of a relationship between cause and effect . . . so the police officer should limit the duration of exposure."

Cpl. Gregg Gillis, the RCMP's national use-of-force co-ordinator, told CBC the force has consulted other research in changing its policy.

"In 2005, we said be cautious about the use of multiple exposures because we're not sure what the outcome might be from that . . . we now have research that sort of speaks to that issue," Gillis said.

"So as a result that's why, in our policy, we're confident in saying there's a risk to using multiple exposures but it's not an absolutely forbidden issue."

Gillis cited studies from two researchers.

The first, by American Theodore Chan, did not look into multiple shocks - instead, he examined police officers who had received a single five-second shock. The second, conducted by Jeff Ho and published in a journal, only dealt with the effects of repeated shocks on breathing.

Late Wednesday RCMP Commissioner William Elliott sent the CBC a letter insisting the RCMP's new Taser policy does restrict use of the weapons, noting it says the officer's actions must be reasonable and the force used must be necessary in the circumstances.

However, Elliott's letter did not directly address the dropped wording on repeated cycling.

Liberal MP Ujjal Dosanjh said the RCMP is going backward on Taser policy.

Dosanjh, who was a member of the Commons committee that called for curbing Mountie stun gun use, expressed anger at the notion Taser policy has been tightened.

In fact, said Dosanjh, restrictions have been removed.

"The public safety minister has an obligation to call Mr. Elliott into his office and say, 'What are you doing? Why are you not levelling with Canadians? Why are you not levelling with the House of Commons Committee that made recommendations?"'

Dosanjh says it is clear the RCMP is out of touch with the anger Canadians feel about Dziekanski's death.