Const. Kwesi Millington, who was among four officers who confronted Dziekanski at the airport in October 2007, is on trial for perjury for his testimony at a subsequent public inquiry.
The Crown alleges Millington and his fellow officers fabricated a story to justify their use of force.
Prosecutors allege the officers then told those lies to homicide investigators and again at the inquiry in early 2009, particularly when they attempted to reconcile apparent discrepancies between their original statements and an amateur video.
But Millington's lawyer, Ravi Hira, suggested his client had no reason to lie because his decision to repeatedly stun Dziekanski with the Taser was in keeping with his training.
Hira asked Millington why he agreed to provide a statement to homicide investigators in the hours after Dziekanski's death, even after being told he could consult a lawyer first if he wanted to.
"I didn't think I did anything wrong," Millington told a B.C. Supreme Court judge.
"I acted according to my training and I was ready to give a statement."
The officers were called to Vancouver's airport after Dziekanski— who arrived from Poland about 10 hours earlier and spoke no English — started throwing furniture in a secure area of the airport's international terminal.
Millington said Dziekanski appeared agitated when the officers arrived. At some point, Dziekanski picked up a stapler and faced the officers.
Millington said Dziekanski held the stapler at chest level and began moving toward the officers, which he described as combative behaviour. At the time, the court heard, officers were trained with the option to use a Taser if a suspect became combative.
"I believed he was going to attack us, so I acted to stop that from happening," said Millington.
Millington deployed his Taser five times before Dziekanski's arms were handcuffed behind his back. An ambulance was called after one of the officers noticed Dziekanski's ears had turned blue, and he was later declared dead by paramedics.
"It was a traumatic incident," said Millington.
"I have never been to a call where we intervened and someone had passed, so it was quite a shocking incident."
The Crown has highlighted several apparent mistakes in what Millington told homicide investigators immediately after Dziekanski's death.
For example, Millington told an investigator that Dziekanski remained standing after the first Taser jolt and had to be wrestled to the ground. The video clearly shows Dziekanski fall on his own.
Millington conceded Dziekanski wasn't physically taken down, though he said that's what he believed happened when he provided his statement.
The Crown argues similar errors in the officers notes and statements prove they colluded.
The trial also heard from Janice Norgard, whose former spouse is one of the officer's cousins. She told the court that the four Mounties met at her place shortly before the public inquiry.
The defence, however, has attempted to cast doubt on the woman's testimony, suggesting that the officers were either not in Vancouver or were busy meeting separately with their lawyers on the days the alleged meeting could have occurred.
Earlier on Monday, a judge rejected a defence application to have the perjury case thrown out.
Hira had argued the Crown, which wrapped up its case last month, failed to provide any evidence to support a conviction.
B.C. Supreme Court Judge William Ehrcke disagreed. Ehrcke ruled the Crown had put forward some evidence that, if true, could support a guilty verdict, though he cautioned that his ruling had no bearing on whether Millington would eventually be convicted or acquitted.
"Without, at this stage, deciding whether (perjury) is an inference that I would draw, I am nevertheless satisfied that it is an inference that a properly instructed jury could draw," said Ehrcke.
Const. Bill Bentley was acquitted of the same charge last year, though the Crown is appealing.
Former corporal Benjamin (Monty) Robinson stood trial late last year and is awaiting a verdict.
Const. Gerry Rundel is scheduled to start his trial on Wednesday.
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