A former Senate law clerk testifying at the Mike Duffy trial in Ottawa admitted that the rules governing a senator's residency do not include a clear definition of a primary residence, how much time a senator should spend there or the type of residence it needs to be.

It's the vagueness of these rules, specifically the rules of residency that, in just the second day of this trial, has begun to form part of Duffy's defence. The 68-year-old suspended senator has pleaded not guilty to 30 charges of fraud and breach of trust, and one count of bribery.

﻿Residency is one of the central issues in the case against Duffy. He designated his home in P.E.I. as his primary residence, and maintains that's the case, making him eligible to claim meals and living expenses for his time in Ottawa, even though he has lived in Canada's capital since the 1970s for work. The Crown disputes that P.E.I. is Duffy's primary residence.

The issue of primary residence is why the first witness at the trial, former Senate law clerk Mark Audcent, could play such an important role in the case. Audcent went over in some detail the rules and regulations regarding the eligibility of becoming and remaining a senator. Indeed, one of his duties as clerk was to brief those who had been named senators about the criteria for remaining qualified as a senator, he told Crown prosecutor Mark Holmes at the Ottawa provincial courthouse.

Four criteria

Audcent said he would break those criteria into four parts:

Attendance.

Obligation not to show foreign allegiance.

Property qualifications.

Residency.

Holmes questioned Audcent about what he would do if he thought someone had not met one of those eligibility requirements. Audcent said his role was that of a resource person and not a policeman.

Instead, he said, if the prime minister wanted to recommend a candidate for the Senate, there had to have been a pre-vetting process to determine whether that person qualified in the first place.

Ultimately, Audcent said, it's up to the Senate as a whole to decide whether a person does or doesn't meet the criteria to be a senator, and whether he or she should vacate the position.

On the issue of residency, he said that, according to the Constitution, a potential or current senator must be a resident of the province for which he or she is appointed.

Mark Audcent, a former Senate law clerk, is cross-examined by defence lawyer Donald Bayne, right, at the trial of Mike Duffy in Ottawa Wednesday in this court sketch. Audcent was testifying about Senate rules on residency. (Greg Banning)

While there is no one defining criteria within the Senate administration rules that defines residency, Audcent explained, there are "indicators of residence." Those include physical presence at the residency, the place where his or her home is and where family lives, and where that individual votes, pays taxes, and receives government and health service and has social connections.

"Every indicator is just part of a package, residence is a question of fact," he said. "You gather these indicators together and you look at the whole picture. There is no indicator that is absolute."

But Donald Bayne, the lawyer representing Duffy, said that since the constitution required a senator to be a resident of the province they are appointed, that made his residence in P.E.I. his most important residence.

To back up his point, Bayne put pages of the concise Oxford English Dictionary in front of Audcent, and had him read the definition of primary as "of chief importance or principal."

He also asked Audcent about whether specific definitions of primary or secondary residences could be found in the those administrative rules.

"I looked hard but I could not find a definition of primary or secondary residence. Is there one?" Bayne asked.

"Not that I'm aware of," Audcent said.

Audcent agreed with Bayne that there was nothing in the rules that says senators must spend a certain period of time at their primary residence.

As well, Audcent agreed that the rules also do not cover how long a primary residence has to have been owned, whether it has been owned longer than a secondary residence or which residence is worth more. Also, Audcent agreed, there is nothing in the rules that prohibit a primary residence from being a cottage or seasonal structure.