Line of fire: A British police officer trains using a Taser gun. The stun guns were issued to a select number of U.K. police forces as part of a pilot scheme in 2007.

Credit: AFP

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TORONTO: A new Canadian study questions police claims that Taser stun guns don't affect the heart. Experiments reveal that, that in animals at least, the Taser can dangerously increase the speed at which it beats.

"Contrary to prior theory, we describe how under certain circumstances the Taser can affect the heart," said Paul Dorian, a cardiologist at St. Michael's Hospital's in Toronto, Canada and lead author of the report.

Tasers are used by police forces in the U.S., Canada, the U.K., and increasingly in Australia. Though they have never been directly implicated in a death, an inquest started this week in British Columbia into the death of Polish tourist Robert Dziekanski. He died shortly after Canadian police stunned him with a Taser at an airport in Vancouver in October 2007.

What is a Taser?

The Taser is a 'non-lethal' weapon developed by Taser International in Arizona, USA. It's a small, handheld device that shoots two darts between four and ten metres away. It uses compressed nitrogen gas like a paintball gun. The two darts are connected to the Taser with small wires that emit a series of 50,000-volt electrical pulses over five seconds to cause pain and loss of muscle control.

There have been examples of people who have fatally injured themselves following a fall after Tasering and a 2007 study in the Annals of Emergency Medicine reported a case where sudden muscle contraction had led to severe spinal injury. Amnesty International claimed last year that 280 deaths in the U.S. and 16 in Canada have been indirectly linked to the use of Tasers.

The latest report into the safety of the weapon is detailed this week in the Canadian Medical Association Journal and describes tests performed on pigs. In the experiment, a Taser was attached to the chest of a pig and fired for five or 15 seconds.

The authors found that as long as the trigger was pressed and electricity was entering the pig's body, the heart beat so rapidly that it could not pump blood. The doctors then administered adrenaline to the pig to simulate real-world stress – and found that on a few occasions the pig's heart maintained a potentially fatal rapid rhythm for a few seconds after the trigger was released.

"Excited delirium"

Not everyone agrees that this constitutes an unacceptable danger though.

"If Tasers kill people, they should drop dead when the Taser hits them, not hours later," commented Gary Vilke, director of clinical research for emergency medicine at the University of California in San Diego, USA. Vilke, who is an expert on deaths under police custody, said, "10 to 11 per cent of people in a state of 'excited delirium' die no matter what, even if they are in an ambulance."

At a May 2007 meeting of the Society for Academic Emergency Medicine in Chicago, Vilke presented the results of his study which found that Tasering had no lasting effect on 32 healthy police officers it was tested upon. He also argued that pigs are a poor model for human hearts, while the "thousands" of police officers across the world that have been Tasered, without incident (during training exercises) are a much better indicator of safety.

The authors of the new report acknowledge that animal models are not perfect. "[But] most of the basic mechanistic concepts in cardiac fibrillation and defibrillation are derived from animal studies, not humans," they write. "In addition, the safety margins for energy of stun gun discharge established by manufacturers were derived from animal models."

The experts now call for further testing of Tasers to establish the effect of factors such as gender, cardiac diseases, drug use, and duration on the safe use of stun guns.