04/29/2015 08:40 EDT | Updated 08/04/2015 10:59 EDT

Mike Duffy trial: Defence questions ex-Senate finance chief for 4th day

Mike Duffy's lawyer is expected to wrap up his cross-examination of the former head of Senate finance, the fourth day he has questioned her in an Ottawa court about the administration's rules and regulations regarding senators' expenses.

Nicole Proulx returns for her sixth day to the witness box where she has undergone intense, and at times combative, grilling by Donald Bayne. While Bayne may finish his questioning of Proulx, the Crown could re-examine her.

The trial, which enters its 17th day, began April 7 in an Ottawa provincial courtroom. Duffy has pleaded not guilty to 31 charges of fraud, breach of trust and bribery related to expenses he claimed as a senator and later repaid with money provided by the prime minister's former chief of staff Nigel Wright.​

Bayne has argued that the rules guiding senators' expenses were vague, ambiguous or non-existent. He has charged that Senate finance officials provided little oversight and he has suggested they rubber-stamped claims,

He has also suggested that Proulx herself may not be an objective witness, that she had a too cozy relationship with Crown officials, willing to meet with them but not with him about the case.

Proulx, while agreeing many of the Senate rules are broad and that terms like "partisan" activities lack clear definitions, has nevertheless defended Senate finance. She has denied that officials in that department rubber-stamp expense claims, and rejected the accusation that she has a bias in the case.

This week, the trial could hear from former Sun News host Ezra Levant, who will testify about two cheques he received for writing speeches for Duffy.

But the trial is also waiting for testimony from Gerald Donohue, one of the key witnesses, who is recovering from serious health issues. Duffy awarded contracts worth roughly $65,000 to Donohue, but the RCMP have alleged that "little or no apparent work" was done in exchange for the payments.

The Crown has argued that Donohue instead used some of that taxpayer money to pay for inappropriate or non-parliamentary services for Duffy.

Court has heard that Donohue issued cheques for services expensed by Duffy that included payments to an office volunteer, a makeup artist, a photo processing firm and a personal fitness trainer. Cheques signed by Donohue to pay for those services came from either Maple Ridge Media, or later Ottawa ICF, companies owned by Donohue's family, court has heard.