The exoneration of Senator Mike Duffy on 31 charges of fraud, bribery and breach of trust could have significant implications for the cases against other senators under scrutiny for their expenses.

"I think that the cases against the other senators have only gotten weaker after this judgment," said criminal defence lawyer Michael Spratt.

"This judgment has clarified how unclear the Senate rules are and what were the Senate policies and practices in place at the time, he said. "That information certainly would weaken the Crown's case in respect to those types of expenses, maybe to the point where there is no reasonable prospect for conviction."

However, Spratt did say that much of Justice Charles Vaillancourt's decision turned on Duffy's own credibility and reliability.

"So in terms of any prospect of conviction that rely on factors like that, the other cases will have to be looked at in isolation."

So far, only Senator Patrick Brazeau and retired senator Mac Harb face trials in relation to alleged inappropriate housing and living expenses, with each facing one count of fraud and breach of trust.

Last June, Auditor General Michael Ferguson, following a two-year review of Senate spending, sent nine cases to the RCMP for possible investigation.

CBC News has since learned that the RCMP would not pursue criminal charges against some of those senators flagged by Ferguson, but it is unclear which cases. Meanwhile, the RCMP's investigation into Senator Pamela Wallin's questionable expenses is still in the hands of the Crown's office.

But with Vaillancourt's dismissal of all charges against Duffy, a precedent has been set for the standard of review of the evidence in all these potential and current cases, said criminal defence lawyer Joseph Neuberger.

"As long as there can be some connection to Senate business, it's going to be an expense that should be allowed and it's not going to be a criminal act," Neuberger said. "So I think this will have a very serious impact on the other cases and investigations."

Senator Mike Duffy and his wife leave the Ottawa Courthouse after being found Not Guilty of all 31 fraud charges. 1:11

Daniel Lerner, a former Ontario Crown prosecutor, said much of the Crown's decision to prosecute the other senators may rest on how much Duffy's case was specific to Duffy and how much of it can be applied to the evidence about the other senators.

"In that sense it could have a lot of impact if there are similarities," Lerner said. "It could have little impact if there's not those similarities."

'Inconsistent verdicts aren't ideal'

Technically, a future judge is not bound by Vaillancourt's decision, he said. And another judge could come to a different conclusion.

"Inconsistent verdicts aren't ideal. You do want a uniformity of law," Lerner said.

However, if the Crown believes that Vaillancourt erred and there's a basis to appeal the Duffy ruling, they may go ahead and prosecute the other senators, "not worried about inconsistent verdicts, because they think Vaillancourt got it wrong."

Of course, public interest and the resources needed to prosecute will also play a role in the prosecutor's decision to pursue these other cases, Lerner said.

"The amount of resources that was spent on this case, where you got 0 for 31 [guilty rulings] is going to influence the decision in the public interest," he said.

A smiling Duffy exits the courthouse after being cleared of all 31 fraud, breach of trust and bribery charges. (Adrian Wyld/Canadian Press)

Jason Gilbert, an Ottawa-based criminal lawyer, said he doesn't believe the Duffy verdict will have much effect on the Crown's cases against Harb and Brazeau. He said, for example, the Crown is continuing to pursue another sexual assault case against Jian Ghomeshi, even though the former CBC radio host was cleared of all charges in a previous trial.

Crown may learn from mistakes

"But they're not going to do it in a vacuum either, Gilbert said. "They're not going to just shake off Duffy now and put it behind them and move on. They are certainly going to look at the identified shortcomings of [the Duffy] prosecution, identify the mistakes made. [They won't] leave anything to inference the way they largely took [things] for granted in this case."

However, for the senators who haven't been charged, but whose cases are in the hands of the RCMP, Gilbert said the Mounties may look at those "and say in light of Duffy and the findings, 'We're not going to proceed with laying charges.'

"I think they would have to take the outcome of [Thursday's] proceedings and look at that and say 'Listen, we may not have the goods.'"​