The problem with telling lies is that eventually they will come back to bite you, Mike Duffy finds himself in just that predicament. He has now so boxed himself in that escape seems impossible at the moment.
You see even if he is able to prove that as he says P.E.I is his primary residence thus maintaining his Senate eligibility he becomes vulnerable on another front. Eligibility requirements for an Ontario health card state that one must maintain their primary residence in Ontario in order to qualify.
So it appears that Duffy is either eligible to sit in the Senate as P.E.I's representative or to collect Ontario health benefits, I don't see how he can do both. In other words it appears that Duffy may have either defrauded Canadians by claiming a housing allowance he wasn't entitled to, or Ontarians for claiming health benefits he had no right to claim.
His only avenue of escape as far as I can see would be for the Senate's residency requirement to be found lax enough not to require primary residence in his home province which would render the principle that a Senator represents a particular province meaningless.