"I tried to put myself in that situation," cardiac electrophysiologist Zian Tseng said Friday at the inquiry into Robert Dziekanski's death. (CBC)

Robert Dziekanski would have lived if he hadn't been stunned by a Taser when confronted by RCMP officers at Vancouver airport in 2007, a medical expert in sudden death testified Friday at a public inquiry.

Dr. Zian Tseng, a cardiac electrophysiologist at the University of California in San Francisco, has studied in-custody sudden deaths, and his work shows that once Tasers were deployed, the rate of those deaths increased six times, though not all were directly attributed to Tasers, the inquiry heard.

In his testimony, Tseng outlined what happens to the heart when a person is stunned by a Taser. In the Dzeikanski case, he concluded that the Polish immigrant would not have died if he hadn't been jolted by a Taser.

"I tried to put myself in that situation and think about if the Taser was not discharged in that case and he simply struggled with police," Tseng said. "In my opinion, in that kind of scenario, he would not have died."

The Mounties were called to Vancouver airport after Robert Dziekanski started acting strangely in the early hours of Oct. 14, 2007. (Paul Pritchard)

Dziekanski died on the floor of the airport soon after being shocked five times by a police Taser. Four RCMP officers had been sent to the international arrivals lounge in response to reports that Dziekanski was throwing furniture and causing a scene. Within seconds of their arrival, a Taser was deployed to subdue Dziekanski.

Tseng told the inquiry Friday Dziekanski was already in a heightened state of stress, frustrated by the situation he found himself in.

Dziekanski's stress level was made worse by the use of the Taser, which triggered a medical condition known as "ventricular tachycardia," which Tseng described as a dangerous heart rhythm.

The Taser jolts in this case either directly or indirectly led to that condition, which could lead to the heart stopping completely, Tseng testified.

The inquiry heard last month from a cardiology expert, who was paid by Taser International for sitting on its medical advisory board, that Dziekanski's death didn't seem to be related to the stun gun.

Dr. Charles Swerdlow testified Dziekanski's heart didn't stop immediately after the deployment of the Taser, adding that if the heart was affected by electrical current, the resulting heartbeat would be either too fast or irregular.

Not acting in public interest: Dosanjh

Liberal MP Ujjal Dosanjh paid a surprise visit to the inquiry Friday to listen to Tseng's testimony.

Dosanjh, who was B.C.'s attorney general in 1999 and okayed the use of Tasers by police in the province, said he now regrets his decision.

"If I had known all of the information [about Tasers], if I had been given the truth, which I wasn't given, I wouldn't have made the decision I made," Dosanjh said.

He also said lawyers representing the federal government and the Mounties in the inquiry are not acting in the public interest at the inquiry.

The provincial inquiry was called in the wake of Dziekanski's death and is being overseen by Thomas Braidwood, a retired B.C. Court of Appeal justice. Braidwood will make recommendations to prevent similar incidents, and he could make findings of misconduct against the officers or anyone else involved.

Throughout these proceedings, Dosanjh said, the federal lawyers have taken a position of undermining Dziekanski's victimization and defending the role of the RCMP officers and the use of the Taser.

He said the federal lawyers seem to be doing that "because they want to limit the liability of the four officers in the RCMP and the federal government."

"But what they are doing by pursuing that short-term interest is actually preventing the public interest in a larger sense from being served, and that is absolutely not appropriate," Dosanjh said.