Human rights group Amnesty International is renewing its call for a moratorium on Taser use after recent tests commissioned by CBC News and Radio-Canada found some of the stun guns deliver a higher level of electricity than the manufacturer promises.

The tests, conducted by the U.S.-based lab National Technical Systems, used 41 X26 model Tasers from seven police departments in that country. Each weapon was fired six times.

Of the 41 Tasers tested, four delivered significantly more current than Taser International says is possible. In those cases, the current was up to 50 per cent stronger than specified on the devices.

The abnormal X26 model Tasers were made before 2005, prompting some scientists to suggest police should stop using any older versions of the stun guns until they can be tested.

The human rights group has said it believes police forces around the world have relied too heavily on the manufacturer's safety claims. It wants to see more independent tests.

"The fact that Tasers were firing above their specified limits then raises questions as to what of the thousands of Tasers that are out there across Canada and across the United States, how often are they misfiring," said Alex Neve, secretary general of Amnesty International Canada.

TASER INTERNATIONAL OFFICIAL STATEMENT:

"TASER International has reviewed the testing results from the National Technology Systems study various TASER X26 electronic control devices as provided by the Canadian Broadcasting Corporation. The results from the testing are generally consistent with the specifications provided by TASER International and which would be expected from such tests.

TASER acknowledges that there are four data that appear to be outliers — instances where current increased as resistance increased, which would not be expected based on the laws of physics. TASER International intends to contact NTS to suggest that the tests be repeated to verify the results.

TASER International appreciates the continued interest in TASER technology, and sincerely hope that the CBC report will focus on the proven injury reductions law enforcement experience with this technology, rather than using engineering minutiae to confuse the viewer and create a false sense of controversy over a test that confirms the output of TASER X26's are consistent, and well below acceptable safety thresholds."

Arizona-based Taser International makes virtually all the stun guns in use today. They are intended to incapacitate people with an electric shock.

The RCMP says it pulled a random sample of some of the force's Tasers for testing, based on the results of the CBC News/Radio-Canada investigation.

A force communications official, Supt. Tim Cogan, informed CBC News late Thursday that preliminary test results showed the sample of Tasers operated within the manufacturer's specifications.

Pierre Savard, a biomedical engineering professor at École Polytechnique de Montréal, designed the technical procedure for the CBC's testing, based on Taser International's specifications.

Savard told CBC News it is scientifically significant that 10 per cent of the Tasers fired in the tests delivered more current than they are supposed to do, especially since he believes no one is verifying the company's claims.

"I think it's important because Taser is not subjected to international standards," Savard said.

"When you use a cellphone, well, cellphones have to respect a set of standards … for the electric magnetic field that it emits. The Taser, well, nobody knows except Taser International."

Savard said the cause of the increased current could be either due to faulty quality control during the stun guns' manufacturing or electrical components that deteriorate with age.

The findings are troubling, since police officers are trained to aim a Taser at the chest, said Savard, who studies heart rhythms and how they are affected by electrical stimulation.

"When you combine an increased current intensity with a dart that falls right over the heart for somebody who has cardiovascular disease or other conditions such as using drugs, for example, it can all add up to a fatal issue," Savard said.

Need time to examine results, Taser says

For years, police forces across North America assured people that Tasers were safe.

Taser International has said its product is "safer than Tylenol."

Taser said that because of the time needed to analyze the test results and the U.S. Thanksgiving holiday Nov. 27, the company couldn't provide someone for an interview before CBC News made its results public.

However, Magne Nerheim, Taser's vice-president of research and development, sent a written response, acknowledging the CBC tests show four of the Tasers malfunctioned.

Nerheim called the malfunctioning an anomaly — one that could be explained if the weapons are not spark-tested on a regular basis.

Nerheim also suggested the testing be repeated to verify the results. He made no comment about the age of the Tasers and whether there could be an issue of reliability.

During the tests commissioned by CBC News and Radio-Canada, three Tasers didn't fire, even with charged battery packs. Those were set aside and not counted in the final results.

But a Taser that doesn't deploy could create a safety issue for a police officer, Savard said.

"When we are talking about Tasers that don't function, I think it is dangerous for the policeman who would try to use the Taser and the individual response can be aggressive," he said.

The CBC showed the results to several electrical engineers as a peer review of the analysis. They agreed that, at the very least, the Tasers made before 2005 should be withdrawn and not used again until they are tested and proved reliable.