The safety of tasers is questioned again

May 25, 2006
By ALEX BERENSON, New York Times

The safety of Tasers, the electric pistols that are widely used by police, is under new scrutiny after a study by a Wisconsin scientist showed that shocks from the guns cause the hearts of healthy pigs to stop beating.

The finding contradicts previous studies that showed that Taser shocks did not cause heart disturbances in pigs, whose hearts are similar to those in humans.

John G. Webster, a professor of biomedical engineering at the University of Wisconsin who conducted the new study, said the earlier studies contained serious errors because they did not account for the fact that pigs have a thick layer of muscle insulating their hearts from their skin. Humans do not.

Dr. Webster removed the muscle from the pigs' chests and placed Taser barbs close to their hearts before shocking the animals. "The previous research made a mistake," Dr. Webster said. "I was a little surprised. But I believe this research more accurately reflects the anatomy of humans."

While most Taser shots land too far from the heart to be lethal, barbs that penetrate the spaces between the ribs that surround the heart may have the potential to cause electrocution, he said.

Steve Tuttle, a spokesman for Taser International, which makes the weapons, said Dr. Webster's research was flawed and did not reflect the way that Tasers were used in humans. The current from a Taser shock is dispersed through the body rather than running directly into the heart, Mr. Tuttle said in an e-mail statement.

The earlier studies on pigs were financed by Taser International. The Justice Department paid for Mr. Webster's study, which is not yet completed. An abstract is posted on Dr. Webster's Web site, http://www.engr.wisc.edu/bme/faculty/webster--john.html

Tasers are pistol-shaped weapons that fire barbs up to 35 feet, delivering a 50,000-volt shock. Because they propel the barbs with compressed nitrogen instead of gunpowder, Tasers are not considered firearms and are not regulated by the Bureau of Alcohol, Tobacco and Firearms or any other federal agency.

Dr. Ted Chan, a professor of clinical medicine at the University of California, San Diego who has studied the effect of Taser shocks on human volunteers, said Mr. Webster's research did not prove that Tasers could cause lethal heart disturbances.

In his research, which is also financed by the Justice Department, Dr. Chan has shocked more than 100 people and not found any changes in heart rhythms. More sophisticated tests conducted on about a dozen people have also failed to find damage, Dr. Chan said.

"Animal studies can point in certain directions, but ultimately you have to look at humans," he said.

Dr. Chan did add that most of the volunteers he tested were not shocked directly over their hearts.

More than 150 people have died after being shocked by Tasers, according to data compiled by Amnesty International, which has called for a moratorium on use of the guns. The weapons are used by almost 10,000 police departments in the United States and internationally, as well as the military. Tasers have been used or tested on volunteers about 200,000 times, Mr. Tuttle said.

Coroners have attributed most of the deaths to causes other than the Taser shock, like cocaine overdoses. But in a handful of cases Tasers have been listed as the primary or contributing cause.

Doctors and scientists have questioned whether Tasers can cause ventricular fibrillation, a lethal heart rhythm disturbance, as well as acidosis, a dangerous change in blood chemistry. Taser International says that many of the deaths have resulted from drug overdoses and that its weapons are safer than most other ways that police officers can use to restrain people.

Since 2002, Tasers have become popular with police departments because they offer officers a way to incapacitate people without having to touch them and because most people do not appear to suffer long-term injury after being shocked. Concerns about safety hurt Taser sales last year, but they have picked up in 2006, with Taser International reporting $14 million in sales in the first quarter.

In October, the Police Executive Research Forum, a nonprofit group that is dedicated to improving police tactics and strategies, recommended that officers be allowed to use the weapons only on suspects who are actively resisting arrest. Some police departments have allowed officers to use Tasers on people who are simply refusing to follow their orders.

The forum's recommendations are not binding. But police departments that do not follow them could face greater legal liability.

Dr. Webster shocked 10 anesthetized pigs with a Taser after removing the skin and muscle over their hearts. On average, the pigs suffered ventricular fibrillation when a Taser barb was placed within 0.7 inch of their heart, according to the abstract of the clinical trial posted on Dr. Webster's Web site. In humans, the heart is situated 0.4 to 2 inches under the skin, Dr. Webster said.

Ventricular fibrillation is an electrical disturbance that causes the heart to beat irregularly and be unable to pump blood. It causes death within minutes unless the heart's normal rhythm is restored.