Throughout the trial, the judge must make sure that all the evidence presented and all the questions asked are relevant to the case. For example, in most situations, the judge will not allow “hearsay” evidence, testimony based on what a witness has heard from another person.
I doubt if the OSC's allegation against E&Y is using such an evidence:
The OSC documents include an internal E&Y email. One member of the audit team asked another in the email: “How do we know that the trees that Poyry is inspecting (where we attend) are actually trees owned by the company? E.g. could they show us trees anywhere and we would not know the difference?”
Maybe the two members are just newbies in the group or even the internship students who have no experience, while the person in charge won't agree what was saying in the email. Anyway, the E&Y said:“The evidence we will present to the OSC will show that Ernst & Young Canada did extensive audit work to verify ownership and existence of Sino-Forest’s timber assets”.
If E&Y can prove that the audit work performed by E&Y has nothing wrong, then at least it should not be that as easy as reading the financial report or checking the documents, finding that the contracts attachments are missing, or such as things, to find the fraud, even if the company is a fraud.