Gas plant prosecution stumbles as judge rejects expert witness in trial of 2 McGuinty advisers

A judge in the trial of two top advisers to former Ontario premier Dalton McGuinty has ruled a key prosecution witness won't be allowed to deliver opinion evidence in court because he's not independent.

It's a blow to the Crown's case against McGuinty's former chief of staff, David Livingston, and his deputy, Laura Miller.They're both charged with breach of trust and mischief for allegedly destroying government documents and computer files about the billion-dollar cancellation of two gas-fired power plants.

• Crown sets out case in trial of 2 Dalton McGuinty staffers

The witness, Robert Gagnon, was a computer forensic specialist with the Ontario Provincial Policefor more than 20 years. He came out of retirement to work with the OPP on the gas plants case.

The defence argued that he was too deeply involved in the investigation to be an impartial expert witness, and Judge Timothy Lipson agreed.

"The evidence shows Mr.Gagnon conflated the roles of expert and investigator," said Lipsonin the Ontario court of justice at Toronto's Old City Hall.

The judge disqualified Gagnon as an expert witness in part because he had "expressed bias with respect to the guilt of the defendants."

Gagnon was to give opinion evidence on what the judge described as "crucial issues in this trial which bear upon the guilt or innocence of the defendants."

Expert witnesses are permitted to testify about their opinion of what evidence means something other witnesses cannot do. Supreme Court of Canada rulings indicate that expert witnesses must be "impartial, independent and unbiased."

"Mr.Gagnon's original limited role morphed into something much more as the police investigation proceeded," Lipson said in his ruling.

The judge chastised the OPP for compromising Gagnon's independence by failing to take steps to keep him away from the management of the investigation.

"What happened in this case stands in stark contrast to others where careful procedures were adopted by the police during investigations to ensure a police expert's impartiality, the judge said.

"Apart from giving Mr.Gagnon a separate lab to conduct his work, the investigative leads took no measures to ensure that Mr.Gagnon's expert opinion evidence would be independent and impartial.

"He provided investigators with strategic and legal advice," Lipson said.

The judge said the "most concerning example of partisanship" was an email Gagnon sent recommending police charge Livingston and Miller with mischief in relation to data.

In the email, Gagnon speculated that Livingston deleted emails in an effort to hide them because he "had to protect his reputation and that of the party."

The judge described Gagnon's comments as "the kind one would expect to hear from a partisan police investigator, not a supposedly independent and unbiased expert."