An expert on parliamentary rules says the Senate has the power to turf a senator from the chamber, as long as a majority approves the expulsion.

Ned Franks, an emeritus political science professor at Queen's university, said, "The Senate is master of its own house."

Franks cautioned that the removal of a senator cannot be done without cause, but, "If the Senate considers that a senator's behaviour is so egregious that they're unfit to sit in the chamber it can act on it. They don't have to go and ask anyone's permission."

However,although the Senate can strip a senator of salary and benefits for unacceptable behaviour, it's not clear if it can actually declare someone a non-senator unless there's a criminal conviction or the senator has missed two consecutive sessions of the Senate.

Franks, who wrote a book about the parliamentary system called The Parliament of Canada, said, "It's up for grabs," when asked if a senator can be deprived of the title and a seat in the chamber just because of bad behaviour or scandal.

A spokesperson for the Senate said Friday that the Senate has never in its history voted to remove a senator from the chamber, but added that if it chose to do so, the vote would not have to be unanimous.

Former Liberal senator Raymond Lavigne came close to facing such a vote in 2011, after he was convicted of fraud and breach of trust over his use of Senate funds. Lavigne quit his seat following the judge's verdict, just days before the Senate was to hold an historic debate on whether to suspend him from the chamber until his sentencing hearing, at which time it could have voted to remove him from his position altogether.

The 'siesta senator'

The Senate came close to firing a senator at least once before that, even though he had not been charged with a crime. In 1998 it voted to strip Senator Andrew Thompson of his salary and benefits, and suspended him from the Senate.

Thompson, a Liberal, claimed he was too ill to come to work, but showed up at least one day per session so that he technically wasn't in violation of attendance rules. He spent much of his time in Mexico.

The Reform Party attacked him relentlessly, calling him "the siesta senator." At one point, Reform MPs hired a mariachi band to play on Parliament Hill so, they said, Thompson would feel at home.

Even though Thompson produced faxes and letters from doctors attesting he was too sick to attend hearings, the Senate voted 52-1, with one abstention, to suspend him without pay.

The Senate held back from the final step of expelling Thompson from the chamber and declaring his seat vacant. However, the Conservative senators who voted no or abstained did so because they wanted to go further and take his title and seat away from him. Thompson remained suspended until he retired two years later.

Audited senators have not been fired 

None of the three senators found to have been inappropriately claiming living and travel expenses have been sanctioned over the matter by the Senate, although Senator Patrick Brazeau is now suspended because he is facing criminal charges in a separate matter. He was expelled from the Conservative caucus at the time of the charges.

Both Liberal-appointed Senator Mac Harb and Conservative-appointed Senator Mike Duffy have resigned from their respective caucuses. Conservative Senator Pamela Wallin, whose travel claims are still being audited, has also left her caucus.

When the audits on the three senators were released, it was revealed that Duffy had already repaid $90,000 for invalid expense claims. Senator David Tkachuk, head of the senate committee that received the audit, declared Duffy's case was closed.

But a day later the government admitted the prime minister's chief of staff had personally given Duffy the money to cover the reimbursement. The next day, media reports suggested Duffy might have been double-billing the Conservative Party and the Senate for his appearances at election campaign events.

In the light of those events, the Senate, as reported by CBC News, may ask for Duffy to be audited a second time for possible additional violations.

The RCMP is examining the expense claims of the three senators who were audited, and if criminal convictions result, they could lose not just their paycheques, but their rights to be called senator.