An Ontario court judge will be asked to dismiss all criminal charges against two senior staffers in former Ontario premier Dalton McGuinty's office accused of destroying government records related to the controversial cancellation of two gas-fired power plants.

Lawyers for David Livingston, who was Mr. McGuinty's chief of staff, and Laura Miller, the deputy chief of staff, will seek a directed verdict of acquittal on charges against their clients. The directed-verdict application calls on the judge deciding the case to dismiss the charges before the defence has even called any witnesses, arguing the Crown has not proven its case. Justice Timothy Lipson of the Ontario Court of Justice will hear arguments on Friday.

The application comes after nearly three weeks of testimony in court at Toronto's Old City Hall about events that took place during Mr. McGuinty's final days in office. The purging of documents while the McGuinty government was under intense pressure to produce records has formed the backdrop to the trial.

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Mr. Livingston and Ms. Miller are facing criminal breach of trust and mischief charges in connection with the destruction of e-mails and other government records in connection with the Liberals' decision to pull the plug on the two power plants before the 2011 provincial election. Each has pleaded not guilty.

Police allege Mr. Livingston hired Peter Faist, a non-government IT expert and the spouse of Ms. Miller, to "wipe clean" computer hard drives in the Premier's Office just days before Mr. McGuinty stepped down in February, 2013.

Prosecution lawyer Tom Lemon hinted in court on Tuesday that the Crown is considering dropping one or more charges. He said prosecutors want to explore one aspect of the case that, if successful, will make a significant portion of Friday's application unnecessary.

"I've been around long enough to understand your coded language," Justice Lipson responded.

Mr. Lemon asked the judge to give prosecutors until early next week to prepare their submissions. But the judge denied the request, saying all he needs is a bullet-point presentation from the Crown, setting out evidence supporting the alleged offences.

"That's not a tall order given the amount of time that has gone into this case," Justice Lipson said.

He said the Crown has presented the court with two volumes of e-mails that have not been explained, and that he cannot be expected to "guess" which ones are relevant.

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Brian Gover, a lawyer for Mr. Livingston, told reporters outside the court on Tuesday that the Crown has failed to make a case after calling 11 witnesses. "It is our position that after all these days of trial, the Crown has failed to meet its obligation to lead some evidence in relation to each of the essential elements of the three charges before the court," he said.

Mr. Faist, speaking publicly for the first time last week about his role in what was known as "Pete's Project," testified that he was paid $11,000 to wipe clean the hard drives of 20 desktop computers in February, 2013, during the transition from the McGuinty government to Premier Kathleen Wynne.

Mr. Livingston told police investigators in October, 2015, that he instructed one of his deputies, Dave Gene, to make sure Mr. Faist got paid for doing the work, according to his "cautioned" statement (meaning it may be used against him in court) quoted in recently unsealed police documents. "I didn't want him to be doing this off the side of his desk, and so I said, he should be hired," Mr. Livingston said.

When asked by police why Mr. Livingston did not use the government's in-house IT staff to wipe the hard drives, he said Mr. Faist is a "trusted insider," according to the police documents.

The trial has heard that Mr. Livingston sought special access to the desktop computers in the premier's office only after a previous effort by Mr. Faist to erase documents on the hard drives had failed. On Jan. 25, 2013, the day after Mr. Faist tried to install special wiping software on Ms. Miller's computer, Mr. Livingston approached Peter Wallace, then secretary of cabinet, requesting the appropriate access, known as administrative rights, the trial has heard.

Mr. Wallace told police he was never made aware that Mr. Faist had already attempted to delete data, or he would have taken immediate action, according to the police documents. "The notion that they were simultaneously, I now believe to be deceitfully, working behind my back to undertake document destruction on a government of Ontario asset, is alien to me … and something that frankly humiliates me," Mr. Wallace told police.

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Mr. McGuinty is not under investigation and has co-operated with the probe. The trial continues on Friday.