OTTAWA -- A former lawyer inside the Prime Minister's Office has contradicted the Conservative campaign in court, laying out in detail how Stephen Harper's top aide was told of the secret $90,000 repayment of Sen. Mike Duffy's expenses.

Benjamin Perrin's testimony at Duffy's fraud, breach of trust and bribery trial covered the negotiations that transpired between Duffy and the PMO in February and March 2013.

He described how a conference call was set up with Duffy's lawyer Janice Payne to include himself, Nigel Wright, Harper's right-hand man at the time, and Ray Novak -- Harper's principal secretary and Wright's eventual replacement as chief of staff.

Perrin says shortly before the conference call, he sat at a table in Wright's office with Wright and Novak.

It was during that short meeting that Wright told Perrin he would cover Duffy's expenses. Perrin says he looked over at Novak to see his reaction, and saw none.

The testimony contradicts what Conservative campaign spokesman Kory Teneycke said last week -- that Novak was unaware of the payment, and that he was not on the call when the payment was discussed.

Later, on the conference call with Payne, Perrin says that Wright and Duffy's lawyer discussed the details of how he would cover Duffy's expenses.

He told court that Novak was in the room throughout the call, although Wright did all the talking.

The testimony also contradicts Wright's claim that Novak only popped in and out during the conference call, and was not one of the staff members in the loop on his payment.

Harper himself has rejected questions from reporters specifically on Novak's knowledge of the payment.

In June 2013, weeks after the Wright payment broke in the media, Harper told the Commons that Wright had not told anyone in his staff about his decision.