U.S. study raises more questions about stun gun safety

January 25, 2009
CBC News

The Taser stun gun has been advertised and sold as a police tool that can decrease the number of suspect shooting deaths and officer injuries, but a new study suggests its use does not reduce the number of people who die in custody.

The study was conducted by researchers at the University of California San Francisco. They surveyed U.S. city police departments for cases of in-custody sudden deaths in the absence of lethal force in the five years before they started using Taser stun guns and the same period after deployment began. Fifty of the 84 departments approached were able to provide data.

The research group found a sharp increase in the rate of in-custody sudden death in the first full year of Taser deployment compared with the average rate in the five years before the stun guns were used.

"A little bit to our surprise we found a statistically significant six-fold increase in the in-custody sudden death rate in the first full year of Taser deployment, and that rate then declined down near baseline in years two to five," said one of the researchers, cardiologist Zian Tseng.

Tseng testified last May at the Braidwood inquiry, which is looking into the death of a Polish immigrant Robert Dziekanski at Vancouver International Airport in October 2007.

Over the entire reporting period, researchers found the average rate of 1.57 sudden deaths per 100,000 arrests in the 50 cities. In the first full year after stun guns were deployed, the rate was 5.96 per 100,000 arrests, a 6.4-fold increase over the predeployment period.

The study showed that in the first complete year after deployment, the rate of deaths caused by officers using firearms remained high at 15.1 per 100,000 arrests, a 2.3-fold increase over the predeployment period. In years two to five after deployment, the rate of lethal force deaths decreased to 9.1 per 100,000 arrests.

Officers adjusted use, researcher believes

Tseng said his team concluded that police likely changed the way they used the Taser after the first year and that accounted for the drop in sudden in-custody deaths. He thinks the findings point to the importance of stringent policies for Taser use.

Tseng told Vancouver's Braidwood inquiry that a normal healthy person could die after a jolt from the stun gun if the shock went into the chest during a vulnerable point in the heart beat.

The U.S. researchers acknowledge their study is "purely observational" and has limitations because they did not ask police for details about the reported in-custody deaths and did not ask whether the Taser had actually been applied in those incidents, meaning the weapon was used only in a subset of these deaths.

However, they said, other investigators have suggested that stun guns may cause sudden death by increasing the risk of excited delirium, a much-debated condition in which sudden death occurs after a violent struggle.

Canadian physicians concerned

The Canadian Medical Association has raised concerns in the past about police departments relying on the manufacturer's claims of safety, and has called on police departments to open their databases to researchers.

Dr. Matthew Stanbrook, deputy editor for science at the CMA's Journal, thinks the U.S. study is a good first step toward building a body of work about real-life stun gun use.

"Greater societal pressure needs to be put on agencies on this to release that information for the public good because people are asking serious questions about this," he said.

Taser International, which is based on Scottsdale, Ariz., has been selling the most popular brand of stun gun to police departments in North America since 2001. The company has data on its website that it says shows the number of injuries to police officers has dropped dramatically since the introduction of the stun gun.

The San Francisco study found no change in the injury rate to officers. However, researchers noted in their report that the 10 largest U.S cities where stun guns are used most frequently refused to release their Taser data for the study.