RCMP officers at Vancouver airport discharged a Taser five times while restraining Robert Dziekanski on Oct. 14, 2007. (Paul Pritchard)

A cardiology expert paid by the company that makes Tasers told a public inquiry Tuesday he doesn't think Robert Dziekanski's death was at all related to the controversial stun guns.

Dziekanski died on the floor of Vancouver's airport in the early morning of Oct. 14, 2007, minutes after four RCMP officers confronted him and stunned him several times with a Taser.

Dr. Charles Swerdlow, a cardiac electrophysiologist who receives compensation for sitting on Taser International's medical advisory board, appeared at the inquiry by video conference from California.

Swerdlow said if the Taser negatively affected Dziekanski's heart, it would happen almost immediately after he was stunned.

But he noted that an airport security guard has testified that he checked Dziekanski's pulse three times before firefighters arrived more than 10 minutes after his collapse. Trevor Enchelmaier told the inquiry that each time he checked, Dziekanski had a heartbeat.

"In Mr. Dziekanski's death, we know his [heart stopping] was not immediate, we know he had an adequate cardiac rhythm for a number of minutes following exposure to Taser," said Swerdlow, who works at Cedars-Sinai Medical Centre in Los Angeles and also teaches at the University of California.

"So nothing here fits with direct cardiac electrical stimulation."

Swerdlow also said that if the heart is affected by electrical current, the resulting heartbeat would be either too fast or irregular. The first time anyone noticed anything wrong with Dziekanski's heart was when firefighters arrived and found he had no pulse at all.

An autopsy concluded Dziekanski died of "sudden death during restraint." It's a little-understood term used previously in unexplainable deaths in police custody, including some involving Tasers.

A forensic pathologist, Dr. Charles Lee, testified a day earlier that the Taser may have contributed to Dziekanski's death.

Lee said the stress of being stunned with a Taser and then pinned to the floor, combined with signs of potential alcohol abuse, could have played a part in Dziekanski's heart stopping.

However, he couldn't say how much the weapon contributed or whether Dziekanski would have survived had it not been used.

'Sudden in-custody death'

Swerdlow agreed that "sudden in-custody death" best describes Dziekanski's death, but he disagreed that the Taser could have played any part.

He acknowledged that Tasers could potentially cause indirect stress on a subject's body, which may in turn contribute to cardiac arrest in some situations.

"While I think it's nearly certain Mr. Dziekanski was stressed … whatever stress he was under, it didn't cause the cardiac arrhythmia that led to his death," he said.

The inquiry has heard much evidence about Dziekanski's condition and the care he received after he was stunned, but it isn't clear at what moment the man died.

The security guard and one of the officers both testified they had been checking Dziekanski's pulse and breathing. Several witnesses have said they never saw anything resembling first aid, while others said they saw his pulse checked once or twice.

The chief of the fire unit that responded said it didn't look like anyone had been monitoring Dziekanski, and when he arrived, the man was likely already dead.

Taser International has long maintained the weapons are safe, insisting that there is no proof it has directly caused any deaths in Canada.