Scientists who conducted tests for CBC News/Radio-Canada finding that some stun guns produced higher than advertised voltages are disputing suggestions by Taser International that their data was "scientifically flawed."

Roger Barr, among the engineers who reviewed the testing protocol, dismissed Taser International's concerns and said the CBC-commissioned tests were based on solid practices.

"The CBC tests measured the voltages and currents that came out of Tasers when they were fired. It measured in a systematic and professional way," said Barr, a biomedical engineering professor at Duke University in Raleigh, N.C.

The procedure, conducted by U.S.-based lab National Technical Systems, found that 10 per cent of the stun guns produced more electrical current than the weapons' specifications.

"This is not simply a matter of opinion," said Barr. "This is an issue of objective evidence, and perhaps not all of the evidence is in, but it is not a case where one can simply disregard some of the findings because someone else disagrees with them."

Taser International said CBC made scientific errors by failing to spark-test the weapons before firing them, which the company recommends police officers do on a regular basis.

Spark test a red herring: engineer

University of Montreal biomedical engineer Pierre Savard, who designed the testing system, says the spark-test issue is a red herring, since some Tasers delivered a higher electrical current after the first firing, the equivalent of a spark test.

"A spark test would last probably less than one second. And for two Tasers that showed abnormal currents, we were able to do repeated measurements after one or two seconds, and the current was still abnormally high after those initial tests."

Savard points out that the written instructions from Max Nerheim, Taser International's vice-president of research and development, made no mention of a spark test.

Taser International also criticized the CBC tests over the way the tests replicated electricity moving through a human body, which was measured in ohms. Prior to the tests, the company advised using a resistance of 250 ohms, but later said it should have been 600 ohms.

Savard says these changes in the testing protocol highlight a significant problem for anyone wanting to do independent testing of the Tasers.

"I think the real problem is that there's no international standard in how to test these devices and so the company is changing the protocol from one value of the resistance to the other," said Savard.

Savard said there's a need for more independent studies of the devices, but it would require a uniform protocol.

The CBC commissioned the tests using Tasers from seven unidentified police departments in the U.S., who agreed to provide the guns on the basis their identities would remain unknown.

Of 41 older-model X26 Tasers tested, four delivered significantly more current than Taser International advertised was possible. In some cases, the current was up to 50 per cent stronger than specified.

The X26 Tasers were manufactured before 2005 and are one of the most commonly used models.

Agencies review use of older Tasers

The findings prompted Savard to recommend police stop using any older versions of stun guns until they are tested.

Since then, several police agencies have begun checking their inventories for older devices. B.C, Alberta, Nova Scotia, Quebec and the RCMP have ordered police to suspend the use of Tasers bought before 2005 and in some cases before 2006.

On Thursday, Alberta Solicitor General Fred Lindsay announced a plan to gather up about 400 Tasers from police agencies around the province, purchased before Jan. 1, 2006, and have them tested.

"The plan is to test all of the approximately 400 Tasers in question to determine if they are working within the manufacturer's specifications," said Lindsay. "We'll await the results of those tests before deciding on next steps."

"In the interest of public and police officer safety, my department is currently in discussions with the Northern Alberta Institute of Technology and the Southern Alberta Institute of Technology to implement a testing protocol for all X26 model Tasers purchased by Alberta police services before Jan. 1, 2006," said Lindsay.

Some provinces appear to be leaving the decision to pull the older Tasers to individual police departments.

Winnipeg police plan to remove the older Tasers from service and have them tested. While they couldn't say how many of the about 200 Tasers in their stockpile are being pulled from use, police said they are focusing their efforts on locating devices manufactured prior to 2005.

"These devices are being pulled from service," Const. Jason Michalyshen said.

Taser International has always insisted there is never a need to test a Taser's electrical output after it leaves the factory. In news releases over the past few days, however, the company is now offering to help police get their Tasers tested.

"Taser International welcomes proper testing of its devices and has provided its factory test protocols to test laboratories in Canada."