The review by the Justice Department, which will initially involve 30 such cases, follows the rapid growth in deployment of stun guns as a nonlethal alternative to bullet-firing weapons.
The department's research arm, the National Institute of Justice, said there have been 184 such deaths since 1986, the overwhelming majority since 2000. Amnesty International, which has called for a moratorium on stun gun use, says there have been roughly 160 deaths in the past five years.
The study will not look at whether the use of stun guns was appropriate, John Morgan, the institute's assistant director, said Wednesday. Instead, researchers will make medical assessments of the 30 cases, which include deaths that were attributed to a stun gun and some in which authorities could not determine whether a stun gun caused or contributed to a death, he said.
Two deaths occurred in 1986, one in 1990 and the rest since 2000, Morgan added.
In the remaining 154 cases, stun guns were ruled out as a factor in the deaths, but the study could eventually include those deaths as well, he said, saying the review could take up to two years.
"We hope this will help improve less-lethal technology generally," Morgan said. "If we find a particular operating characteristic is contributing to a problem, we hope that will be way to improve that technology."
Taser International of Scottsdale, Ariz., the largest maker of stun guns, said that the devices have saved more than 9,000 lives because police officers have been able to the weapon instead of handguns that fire bullets. Tasers deliver a 50,000-volt jolt through two barbed darts that can penetrate clothing.
"Given that the NIJ conducted a similar study on pepper spray which effectively ended the debate regarding its safety, we are hopeful this study will lead to the same outcome regarding electro-muscular disruption devices," Taser vice president Steve Tuttle said.
Dalia Hashad, director of Amnesty's USA Program, said the study is a good first step. "We've been asking the federal government for the last six years to take seriously that people are dying after being shot by this weapon," Hashad said.
A government study last year said more than 7,000 of the nation's 18,000 police agencies used Tasers, up from 1,000 in 2001.
Many of those who died were high on drugs, mentally ill or otherwise agitated, according to an Amnesty International report released in March. Many deaths in the past year occurred after victims were hit by Tasers at least three times and, in some cases, for prolonged periods, the report said.
Some police agencies have tightened their rules on stun-gun use following Taser-related deaths.
One goal of the new study is to get a better understanding of how the body reacts when hit by electricity from the devices.
Researchers will include medical examiners, pathologists, cardiologists and other experts, said Dr. Robert Hunsaker, president of the National Association of Medical Examiners and co-chairman of the group that is designing the study.
The International Association of Chiefs of Police, which has called for careful monitoring of stun gun use, also will be part of the review.