Nearly six years after a Polish immigrant died at Vancouver's international airport, the first of four RCMP officers involved in his death will stand trial on charges of perjury related to a public inquiry into the case.

Const. Bill Bentley was among four officers who confronted Robert Dziekanski in October 2007, stunning him multiple times with a Taser within seconds of arriving on the scene in response to reports of a man throwing furniture.

Dziekanski died on the airport floor. A coroner's report found he suffered a fatal heart attack and deemed the death a homicide.

But a confidential legal opinion obtained by CBC News suggests the perjury cases against the police may be difficult to prove in the Vancouver court room.

At the inquiry, the Mounties' versions of what happened were at odds with amateur video of the incident.

The officers insisted they were simply mistaken when they initially claimed Dziekanski had come at them screaming with a stapler, and had to be wrestled to the ground.

Inquiry commissioner Thomas Braidwood called their explanations "self-serving," "patently unbelievable" and "deliberate misrepresentations of what happened made for the purpose of justifying their actions."

A special prosecutor indicted them all for perjury, citing 28 allegations of deliberate attempts to mislead the inquiry.

Bentley — who is on administrative leave in Ontario — will be first in court, followed by the others over the next year.

"The officers [lied], of course," says Robert Dziekanski's mother, Zofia Cisowski. "Everybody knows that and covered up."

But CBC News has obtained a confidential legal opinion written for the RCMP by Len Doust, a prominent B.C. lawyer, who successfully prosecuted Air India bomb-maker Inderjit Singh Reyat, among several other high-profile cases.

Doust wrote that while troubling, the officers' testimony "does not likely amount to perjury."

The discrepancies can be explained by "the frailties of human memory", the quick pace of the "intense circumstances" and "the impact of Mr. Dziekanski's death on the Officers," Doust writes.

But Vancouver lawyer Cameron Ward says Doust's opinion shows these cases are not clear cut.

"It's one thing to make mistakes while on the witness stand. It's quite another to lie while under the oath with the intention to mislead the court," Ward said.

Dziekanski's mother says acquittals would prolong her quest for closure.

"What we can call this is if not perjury if not lying and covering up? What we can call that?" said Cisowski.

Taser use by police in B.C. has fallen 87 per cent since Dziekanski's death six years ago.