A criminal trial into the purging of government records in former Ontario premier Dalton McGuinty's office has been postponed for one week.

David Livingston, Mr. McGuinty's former chief of staff, and his deputy Laura Miller were to stand trial on Monday in connection with the destruction of e-mails and other records related to the controversial cancellation of two gas-fired power plants prior to the 2011 election.

Mr. Livingston and Ms. Miller appeared in Toronto's Old City Hall courtroom on Monday, where they each pleaded not guilty to criminal breach of trust and mischief charges in connection with the deletion of the government records.

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The charges stem from police accusations that Mr. Livingston hired a non-government IT expert, Ms. Miller's spouse, Peter Faist, to "wipe clean" computer hard drives in the premier's office just days before Mr. McGuinty left office in February, 2013. The two are accused of compiling a list of senior Liberal staffers whose computer records were to be deleted, all of whom police allege were involved in discussions around the Liberals' costly decision to scrap the gas-plant projects in Mississauga and Oakville, Ont. The provincial auditor pegs the cancellation tab at $1.1-billion.

"The police investigation was sparked by a politically motivated complaint," Brian Gover, Mr. Livingston's lawyer, said in Ontario Court of Justice. The opposition Progressive Conservatives, he said, "were seeking to maximize the gas-plant scandal."

Court documents prepared by the Ontario Provincial Police as part of their investigation say Mr. Livingston avoided leaving public records of many of his discussions by double deleting e-mails and communicating by BlackBerry messenger. Mr. Faist, who is co-operating with investigators, told police he was instructed by Ms. Miller to "wipe off personal data" on about 20 computers in the premier's office. Between Feb. 5 and Feb. 7, 2013 – just days before Kathleen Wynne was sworn in as Mr. McGuinty's successor – Mr. Faist erased 632,118 files, accounting for 13 per cent of all the data on the 20 hard drives, the documents allege.

Mr. McGuinty, who is not under investigation and who is co-operating with the probe, has told police his chief of staff was ultimately responsible for all of the activities that took place in his office.

In seeking a one-week delay on Monday to what is expected to be a six-week trial, Mr. Gover slammed the quality and timeliness of the information disclosed by Crown prosecutors. Justice Timothy Lipson agreed to postpone the trial until Sept. 18.

"The police notes are cryptic, unusually sketchy," Mr. Gover said, adding that in some instances, there are inconsistencies between two police officers' notes of the same witness. Mr. Gover also said prosecutors have cut their proposed list of witnesses in half to 12 without explanation.

Prosecutor Tom Lemon explained that the witnesses removed from the Crown's list are individuals whose testimony would duplicate that of other witnesses.

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Judge Lipson agreed, saying, "What it sounds like to me is the normal assessment the Crown makes of his or her case."

Mr. Lemon said prosecutors were prepared to provide a table for defence lawyers, outlining new information witnesses have provided compared with what they had previously given. Prosecutors plan to re-interview several witnesses this week.

Prosecutors should take thorough, careful notes of any new interviews, Judge Lipson cautioned.

"It would be very unfortunate if we had to repeat this exercise again for interviews taking place in the future," he said.