San Francisco cardiologist and electrophysiologist Zian Tseng became interested in the use and effects of tasers after a taser-related death in San Francisco in January, 2005. In an interview with the San Francisco Chronicle, Dr. Tseng suggested tasers could induce cardiac arrhythmia.
"Shortly thereafter I was contacted by [Taser International, Inc.] directly to reconsider my statements to the media," he said. "They even offered to ... give me grant money for research."
Much of the scientific justification for the safety of tasers is based on formulae that don't examine their use in the "real world," Dr. Tseng said.
"What's not allowed in these theoretical calculations are worst-case scenarios," he said. "Tolerability in healthy volunteers under optimal conditions does not mean safety."
Many of the most commonly cited studies that show the devices are safe were financed by Taser International, Dr. Tseng said. Several of the authors of a 2005 study are Taser employees.
Many of these studies use simulated stun guns rather than tasers themselves, and a study on humans monitored only the subjects' heart rate before and after the shock - not during it, which is when other studies have shown that heart rates were most dramatically disrupted.
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The ability of tasers to disrupt a person's heart rate fatally increases if the weapon's barbs are embedded close to the heart or if the subject is affected by high adrenalin, heart disease, drug use or high blood acidity, Dr. Tseng said.
Several people have died after taser-related incidents in Canada since the devices were introduced in 1999, but no autopsy has found them responsible. Dr. Tseng said a fatal arrhythmia caused by a taser wouldn't show up in an autopsy.
"If somebody dies and they find no cause of death, it's almost certainly an arrhythmic death," he said, adding that tasers can affect a person's heartbeat long after the event.
Dr. Tseng said tasers may be able to play a role in law enforcement, but the way they're used should be re-examined. He recommended police avoid tasering subjects near the chest area and carry "dummy-proof" automatic external defibrillators with them to ensure they can aid anyone who goes into cardiac fibrillation.
B.C. sheriff services Superintendent Paul Corrado and senior use-of-force instructor Greg Ducharme presented the B.C. sheriffs' policy on taser use. They've been using tasers to assist in prisoner management since 2001.
Sheriffs don't routinely carry tasers and have to be trained beforehand, Supt. Corrado said, but they aren't told of any safety risks.
The presentations were part of a "study commission" headed by former Appeal Court judge Thomas Braidwood looking into taser use in the province. It's the first part of a provincial taser inquiry; the second part will focus on the death of Robert Dziekanski after he was tasered in Vancouver International Airport in October, 2007.
© 2008 The Globe and Mail