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What a surprise. File this one under the Department of Duh, because anyone who's been following the history of Taser use (524 Taser-related deaths so far) has figured out there can't be that much smoke without some fire.

The electrical shock delivered to the chest by a Taser can lead to cardiac arrest and sudden death, according to a new study, although it is unknown how frequently such deaths occur.

The study, which analyzed detailed records from the cases of eight people who went into cardiac arrest after receiving shocks from a Taser X26 fired at a distance, is likely to add to the debate about the safety of the weapons. Seven of the people in the study died; one survived.

Advocacy groups like Amnesty International have argued that Tasers, the most widely used of a class of weapons known as electrical control devices, are potentially lethal and that stricter rules should govern their use.But proponents maintain that the devices — which are used by more than 16,700 law enforcement agencies in 107 countries, said Steve Tuttle, a spokesman for Taser — pose less risk to civilians than firearms and are safer for police officers than physically tackling a suspect.

The results of studies of the devices’ safety in humans have been mixed.

Medical experts said on Monday that the new report, published online on Monday in the journal Circulation, makes clear that electrical shocks from Tasers, which shoot barbs into the clothes and skin, can in some cases set off irregular heart rhythms, leading to cardiac arrest.

“This is no longer arguable,” said Dr. Byron Lee, a cardiologist and director of the electrophysiology laboratory at the University of California, San Francisco. “This is a scientific fact. The national debate should now center on whether the risk of sudden death with Tasers is low enough to warrant widespread use by law enforcement.”

The author of the study, Dr. Douglas P. Zipes, a cardiologist and professor emeritus at Indiana University, has served as a witness for plaintiffs in lawsuits against Taser — a fact that Mr. Tuttle said tainted the findings. “Clearly, Dr. Zipes has a strong financial bias based on his career as an expert witness,” Mr. Tuttle said in an e-mail, adding that a 2011 ificant risk of cardiac arrest “when deployed reasonably.”

However, Dr. Robert J. Myerburg, a professor of medicine in cardiology at the University of Miami Miller School of Medicine, said that Dr. Zipes’s role in litigation also gave him extensive access to data from medical records, police records and autopsy reports. The study, he said, had persuaded him that in at least some of the eight cases, the Taser shock was responsible for the cardiac arrests.