Sen. Mike Duffy is hoping to extract a lofty sum from the Senate and the RCMP, arguing they unfairly subjected him to a witch hunt that resulted in gross Charter violations and salary loss that now demand some form of compensation.

But legal experts well-versed on civil lawsuits of this sort say it could be a tough slog for the P.E.I. senator.

At the heart of Duffy's $8-million lawsuit is a claim that the Red Chamber and the Mounties ran roughshod over his rights in their dogged pursuit of a scapegoat for public outrage over questionable expenses.

Duffy claims he was "threatened, cajoled, arm-twisted and rebuked" by former prime minister Stephen Harper's office to publicly admit wrongdoing even though he maintained all expenses were above board.

The Conservative-controlled Senate was then the "government's servant" and booted him from the upper house to serve a political agenda when things went awry. The RCMP, in turn, hastily assembled a criminal case that unfairly subjected Duffy to humiliation among other ills.

You can claim whatever you want doesn't mean you're going to get it. This is a little different than the proverbial slam dunk. - Robert Houston

In his statement of claim, filed Thursday, Duffy said his Charter rights under section 7 (the right to life, liberty and the security of person), section 11(d) (the right to be presumed innocence) and section 12 (freedom from cruel and unusual punishment) were ignored throughout this scandal by both the Senate and the police.

"The system makes it really hard to allege a violation of the Charter based simply on a suspension from a position, loss of pay and the mere fact you were charged for a crime; it's hard to argue that leads to a Charter violation when you're ultimately acquitted and your job is reinstated," Carissima Mathen, an associate professor of constitutional law at the University of Ottawa, said in an interview.

"The government enjoys a significant level of immunity."

The 31 criminal charges against Duffy were dismissed by an Ontario judge last year; Justice Charles Vaillancourt found all of his expenses reasonable and instead pointed the finger at Harper's PMO. Thus, Duffy's argument goes, he should now be made whole by the institutions that subjected him to abuse.

"We don't have a court precedent — other than for a wrongful conviction — of Charter damages in the millions of dollars.​ The case law just doesn't support damages at that level," she said.

Judge Charles Vaillancourt cleared Senator Mike Duffy of all 31 criminal charges he faced including fraud, breach of trust and bribery. (Justin Tang/Canadian Press)

And while Vaillancourt found Duffy did nothing criminal, those legal findings cannot now be automatically applied to a civil case, Mathen said.

"The standards of proof are so different ... A different court is not necessarily bound by everything Vaillancourt said. Another judge might say, 'We don't actually find his expression of opinion, or the conclusions he drew here, part of the ratio of this case.'"

Importantly, Duffy also argues the Mounties were negligent in their investigation because they did not give him ample time to respond to the criminal charges he was facing.

But Robert Houston, an Ottawa-based lawyer with expertise in civil litigation, said Duffy's lawyer, Lawrence Greenspon, will have an "uphill battle" proving such a claim in court because there are few other successful examples in Canadian law.

"The tort of negligent investigation is relatively new as these things go in the law of the land," he said, noting it was only established in 2007 after the Hill v. Hamilton-Wentworth case made its way to the Supreme Court.

Jason Hill was wrongly convicted and later released after 20 months in jail. He claimed Hamilton, Ont. police acted maliciously and negligently in fingering him for a series of bank robberies. While the court established police can be sued for negligent investigations, they said they acted appropriately in Hill's case.

So, even when a man was wrongfully subjected to jail time, the court did not find he was entitled to compensation.

Greenspon, for his part, is confident he can succeed where others failed.

"I've been doing negligent investigation cases against the Ottawa Police, and the OPP and the RCMP for more than 35 years," Duffy's lawyer said Thursday after announcing the suit. "That single item, the failure to give somebody a fair chance to respond to the accusations — before you make the decision in your own mind that you're going to charge them — is really an important factor and it's in play here as well."

'Uphill battle' to prove RCMP negligence

As for Duffy's claim that the whole affair has ruined his standing among the Canadian people, Houston said there are few examples of plaintiffs collecting large sums of money for damage to reputation.

"I could claim my reputation is worth a lot of money, but how much is a lot? It makes for good headlines to say you're suing for $6.5 million but there has never been an award anywhere remotely in that range," Houston said. (Duffy's suit seeks $6.5 million in general damages, $300,000 for loss of income and benefits and $1 million in punitive damages.)

Houston pointed to the seminal defamation case Hill v. Church of Scientology of Toronto, in which a Crown prosecutor, Casey Hill, sued the church after it falsely claimed on TV he had knowingly misled a judge and tampered with sealed documents. Hill was awarded $300,000 in general damages, a record-setting sum when it was handed down by a jury in 1995.

"You can claim whatever you want doesn't mean you're going to get it. This is a little different than the proverbial slam dunk."

Duffy also argues the Senate was outside of its constitutional authority to suspend him without pay or privileges.

If a judge were to rule in Duffy's favour on this question, it would be "precedent setting," Mathen said, as it would expose the Senate's practices to a court review.

"I would find it strange that the Senate wouldn't have the power to a suspend a member no matter what the circumstances," Mathen said. "Is it really appropriate for the judicial branch to regulate parliamentary activity in this way?"

'No senator has ever been through what Mike Duffy has been through with the Senate,' says Lawrence Greenspon. 10:58

Greenspon maintains what the Senate handed down to Duffy was "tantamount to expulsion," because they barred him from the Red Chamber for an indefinite period. The constitution enumerates when a senator can be expelled, and questionable expenses is simply not on the list.

"It wasn't administrative act that was carried out, but it was an expulsion, the likes of which have never been done before in parliamentary history in this country."