Dalton McGuinty's chief of staff sought special access to the desktop computers in the premier's office only after previous efforts to erase documents on the hard drives had failed, a criminal trial has heard.

Peter Faist, a non-government IT expert hired by David Livingston, the chief of staff, testified on Friday that he could not initially install the software he bought to wipe the hard drives in the premier's office during the transition from Mr. McGuinty to Premier Kathleen Wynne in 2013. He said he attempted to test the software, called White Canyon, on the computer of deputy chief of staff Laura Miller – his spouse – but could not get it to work because she did not have the appropriate access, known as administrative rights.

Mr. Faist, speaking publicly for the first time about his role in what is known as "Pete's Project," signed an investigative assistance agreement in October, 2014, as part of his co-operation with a police investigation into the deletion of the documents. Under the agreement, his statements cannot be used against him, but it does not preclude police from continuing to investigate or possibly charging him.

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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 related to the cancellation of two gas-fired power plants. Each has pleaded not guilty.

The charges stem from police accusations that Mr. Livingston hired a non-government employee with no security clearance, Mr. Faist, to wipe clean the hard drives in the premier's office just days before Mr. McGuinty resigned in February, 2013.

Mr. Faist testified in court in Toronto's Old City Hall that his involvement began in early January of 2013, when Ms. Miller asked him if he knew anyone capable of cleaning personal data off computers in the office.

"I said I could do it myself," he told prosecution lawyer Tom Lemon.

After the initial conversation with Ms. Miller about the project, he said, he began dealing primarily with Dave Gene, also a deputy chief of staff in Mr. McGuinty's office. On Jan. 9, 2013 – three weeks before Mr. Livingston received special access to the desktop computers – Mr. Gene asked Mr. Faist in an e-mail that was read in court, "Hey, were you looking into wiping our computers?"

Mr. Faist testified that he did not actually begin carrying out the task until Feb. 5, 2013, after Mr. Livingston obtained special access to all the computers in the premier's office, allowing him to install software and delete documents.

Court has heard that David Nicholl, Ontario's corporate chief information officer, played a crucial role in helping Mr. Livingston gain the special access used to wipe hard drives. Mr. Nicholl asked government IT managers to set up special administrative access to all of the computers in the premier's office, the trial was told. On Jan. 31, 2013, Peter Wallace, secretary of cabinet at the time, approved the access after Mr. Nicholl told him that six staffers in the premier's office already had administrative access. Mr. Nicholl did not explain, however, that the access requested for Mr. Livingston was, in fact, much more extensive, court has heard.

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Mr. Livingston's executive assistant, Wendy Wai, was provided with the administrative rights, allowing her to use a special password and sign on to any computer in the premier's office. But the access was used instead by Mr. Faist.

In an e-mail to Mr. Faist on Feb. 4, 2013, presented as an exhibit in court, Ms. Wai says, "CAB IT just called, everything is set up and ready to go," referring to Cabinet Office IT. "I just need to log in as myself at each desktop and you should be able to do your part."

Mr. Faist testified that Ms. Miller's assistant, Alexandra Gair, assisted him with wiping the hard drives. She accompanied him when he was in the premier's office and had the names of staffers whose computers were to be wiped written on a yellow sticky note, he said.

Mr. Faist has told police he was instructed by Ms. Miller to "wipe off personal data" on 20 computers in the premier's office. Between Feb. 5 and Feb. 7, 2013 – just days before Ms. Wynne took office – Mr. Faist erased 632,000 files, accounting for 13 per cent of all the data on the 20 hard drives, police documents allege.

Mr. Faist testified that he submitted an invoice dated Jan. 28, 2013, in the amount of $11,017.50 to the Liberal Caucus Service Bureau.

Because his testimony will continue on Monday when the trial resumes, Mr. Faist is not allowed to talk to anyone about the case while he is a witness. Justice Timothy Lipson suggested to Mr. Faist that he should spend the weekend at another residence, and not at home with Ms. Miller.

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Mr. McGuinty is not under investigation and has co-operated with the probe.