Canadian medical researchers are disputing the theory that stun guns do not cause irregular heart rhythms that are sometimes fatal.
Tests had shown that Taser shock could cause fibrillation -- a very rapid, irregular contraction of muscles fibers -- in any muscle, except the heart.
"Bottom line is we think that assumption is incorrect," said Dr. Paul Dorian, a medical researcher from the University of Toronto. "Under certain circumstances, the Taser electrical discharges can, in fact, cause the heart muscle to beat and to beat very fast."
Dorian and his team shocked six pigs with stun guns looking for signs of ventricular fibrillation (VF) and other adverse heart effects. The results echo a recent Chicago study, where prolonged stun gun shocks caused VF.
Two pigs died in the Chicago study. One pig died of VF in Dorian's study and the other five pigs showed cardiac disturbance.
When it occurs in humans, VF can be lethal, Dorian said.
"When this rapid irregular heart rhythm occurs, the heart doesn't beat effectively," Dorian told CTV News. "No blood is pumped from it, and the victim, unless they get CPR and gets an electrical shock to the heart, will die within 10 minutes."
In response to the Toronto study, manufacturer Taser International said it will present results from three cardiac studies of its own later this month at the Heart Rhythm Conference in San Francisco, California.
"Taser International is dismayed by attempts to present this information as something it is not," the company said in a statement.
"I can understand if they're dismayed," Dorian said. "I'm dismayed as well. Dismayed that we have a technology that potentially can cause harm."
When Victoria police conducted Canada's first Taser trials in 1999, VF was the medical problem they were most concerned about.
But no one was considering the adverse effects of another medical condition caused when muscles are shocked and contract too quickly. High levels of acidity, or low levels of alkalinity in the body fluids, including the blood, can cause acidosis.
"The problem with acidosis is that the organs don't function properly when the acids are present in the blood," Dorian said.
Inspector Darren Laur, who spearheaded the Victoria Taser trial, told CTV News in an email that VF was the only medical concern of their research.
"I was not involved in any studies surrounding acidosis," he wrote.
Ken Stethem, a use-of-force expert from Washington, D.C. said acidosis, which worsens if victims are stunned repeatedly, needs to be considered in the Taser debate.
"These devices being used and backed up by policies that don't limit the number of stuns of the length of the exposure times -- it's hard to believe how that would support public safety," Stethem said.
The officer who is in charge of the Taser program for the Victoria police department told a public inquiry Tuesday that he's uncertain if Tasers cause death.
"I think I would be negligent as a police trainer if I stood up here and said they don't cause death," Constable Mike Massine told inquiry commissioner Thomas Braidwood, a retired B.C. Court of Appeal judge who is conducting the first public inquiry into the controversial use of Tasers.
"I don't know if they do. I don't know if they don't," the officer added. "Maybe there is a correlation, I don't know. I hope when we find out what it is, I hope we find that silver bullet."
Massine said putting a moratorium on Tasers would cause a knee jerk reaction, adding stun guns are a necessary tool for officers facing violent suspects.
The inquiry, which started Monday in Vancouver, is scheduled to continue until May 23.
With a report from CTV British Columbia's Peter Grainger
