The studies that have been done to determine the risks of the Taser stun gun are flawed, a Vancouver epidemiologist told a provincial Taser inquiry Friday.

"I don't think you can extrapolate the results to the real world," said Dr. Keith Chambers.

He recommended that until more research is done to resolve the many unanswered questions about the risks and benefits of the weapon, limits on its use, with standardized guidelines, should be put in place.

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Chambers said the "genie is already out of the bag," meaning it may be too late to conduct proper controlled trials of the weapon. But outcomes could be tracked with better systems of data collection.

He said one of the problems with existing research studies is that the circumstances in them don't occur in the real world. Most of the people on whom Tasers were tested were healthy volunteers who received a single five-second electrical jolt, which incapacitates a person by contracting muscles.

The earliest Taser research involved testing on pigs.

"Animal studies and volunteer studies don't support the real world and don't measure the magnitude of the harms and benefits," said Chambers, an epidemiologist who designs medical research studies.

"In my mind, we have no idea of the relative risk in a large population due to Taser use."

In the studies that have been done, the sample sizes were too small to obtain reliable results, he said. For example, one study used only 66 people.

"It's a huge problem, the sample size," he told inquiry commissioner Thomas Braidwood, a retired judge.

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