Dr. Michael Pollanen spent hours testifying at the inquest into the death of Aron Firman, a 27-year-old schizophrenic who died in June 2010 after an encounter with Ontario Provincial Police.
Pollanen called the incident "an accident" — echoing a finding by Ontario's police watchdog that cleared the officers dealing with Firman of any wrongdoing.
"I have never seen a case where I was confident that you could link a Taser as factor in death, until this case," he told the five-member jury at the inquest.
"This is a first of its kind in Ontario."
Pollanen acknowledged there would be some who disagreed with his finding, particularly as the use of Tasers and their effects is still a growing field of study.
"There is unlikely to be entire uniform agreement on this case," he said. "But I would say it's too parsimonious to say the Taser was uninvolved in death."
Pollanen was careful to note, however, that while the Tasering of Firman was the "most immediate factor" in his death, it was not the only factor.
He described Firman's cause of death as "cardiac arrhythmia precipitated by electronic control device deployment in an agitated schizophrenic man."
But he also said Firman had a "moderately" enlarged heart — though he did not have a specific heart disease — and carried a gene which may possibly have made his heart more vulnerable to injury.
"The fatal outcome in this case likely presents the conjunction of many factors coming together at the same time," he said.
Pollanen made it clear he believed the use of Tasers by authorities had its benefits, and the electric stun gun's role in a fatality was rare, but nonetheless, he said, in some cases the use of a Taser does lead to death.
One possibility the chief forensic pathologist largely dismissed was a suggestion Firman could have died from a syndrome known as "excited delirium," which is sometimes cited as a cause of death in people using cocaine or those with severe mental illness.
A lawyer representing Taser International, which has standing at the inquest, took Pollanen to task on that point, arguing that Firman could very well have died due to excited delirium.
"I'm saying many factors of excited delirium are here," argued David Neave, who also said Pollanen had shown no objective published data which demonstrated that a Taser discharge can cause death.
For his part, Pollanen repeatedly told the inquest it was hard to determine the dividing line between severe agitation and excited delirium.
On that point, the lawyer for the Firman family argued that Firman had been severely agitated in the past but died after he was Tasered.
"It is the family's position in this inquest that if the Taser was not deployed and used on him, he would not have died," Sunil Mathai said outside the inquest.
Mathai added that the family agreed with Pollanen's noting of other factors which could have contributed to Firman's death, saying those elements contributed to "the susceptibility of his heart being captured by the Taser."
Firman's parents were present at Thursday's proceedings, as they have been throughout the inquest.
"It's been a very hard process for us to go through," Firman's father, Marcus Firman, told The Canadian Press.
"This is three years after the event and it brings everything back fresh."
The family is hoping that the inquest will lead to better guidelines around the use of Tasers by authorities and improved response techniques when police have to deal with agitated mentally ill people like their son.
The inquest began in April and was expected to hear from about 20 witnesses.
Aron Firman was a resident at a group home in Collingwood, Ont., at the time of his death.
A December 2010 report from Ontario's Special Investigations Unit said that on June 24 of that year two OPP officers responded to an assault complaint about Firman and found him sitting in a chair outdoors.
Both officers attempted to speak to "an agitated" Firman, according to the report. When they moved to apprehend him Firman got out of his chair and "moved aggressively" towards an officer, it said.
The second officer tried to intervene but was unable to do so as Firman hit her in the face with his elbow, said the report. Firman then moved toward the first officer who responded by discharging his Taser gun at him.
Firman was able to take a few additional steps before falling to the ground and losing consciousness, the report said. He was taken to an area hospital where he was pronounced dead.
In commenting on the case, the SIU director singled out the use of the Taser on Firman.
"In this incident, the Taser's deployment in my view caused Mr. Firman's death," Ian Scott said in his report.
While noting the responding officers had the authority to arrest Firman for assault and had not done anything wrong, Scott pointed out that the Taser is characterized "as a less lethal or intermediate weapon."
"In these circumstances, and in light of Mr. Firman's demonstrated degree of aggression, I am of the opinion that the Taser's deployment was not excessive, notwithstanding the fact that it caused Mr. Firman's demise."
The use of Tasers by police has come under increased scrutiny over the years, particularly in the high-profile death of Polish immigrant Robert Dziekanski, who died after he was Tasered several times during an altercation with RCMP officers at Vancouver's airport in 2007.
A public inquiry in Dziekanski's death has said multiple deployments of the Taser along with a physical altercation contributed to the circumstances that lead to Dziekanski's heart attack. The BC Coroners Service agreed with the conclusions of the inquiry.