OTTAWA -- Mike Duffy's lawyer says he isn't going to rule out calling anyone -- including Prime Minister Stephen Harper -- as a witness in the suspended senator's upcoming trial.

"We're considering any potential witness," Donald Bayne said Tuesday after a brief court appearance.

"At this point, it's too early to rule anything out. But please understand, this isn't being run as a personal or political vendetta."

In July, the RCMP charged the former Conservative senator with 31 counts related to his Senate expense claims.

The charges include fraud, breach of trust and bribery.

Bayne says he hopes to set a trial date for the senator at another court meeting next week. He and Crown attorney Jason Newbauer will talk this week about how soon Duffy's trial can begin.

"This will be his first opportunity for a complete airing of all the evidence before an impartial tribunal and his opportunity to clear his name, to show that he's guilty of no wrongdoing," Bayne said.

The one big question on everyone's mind is how much the prime minister knew about the secret $90,000 payment made by his former chief of staff Nigel Wright to cover Duffy's contested Senate expenses.

Bayne insists the case won't turn into a political sideshow.

"This isn't a political case. This is a criminal case. It's going to be conducted professionally," Bayne said.

"The very strong judiciary in the Ontario Court of Justice will not allow this case to be turned into a political circus and we certainly don't intend to conduct the matter that way."

That said, Bayne acknowledged Duffy's case "absolutely" could go to trial before the next federal election, set for Oct. 19, 2015. The trial itself could last between six and eight weeks, he said.

The senator's poor health should be taken into account when setting a trial date, Bayne added.

"You know he's had two open-heart surgeries," he said. "So part of our concern ... is his physical and emotional and mental health."