In the Aherne v. Chang  O.J. No. 1880 (S.C.J.) case, Master Short considered the following issue:
If surveillance is provided to an independent medical assessor, does it have to be produced to the plaintiff, even if the assessor does not rely on it in forming his or her opinion?
The answer is yes.
In arriving at this conclusion, Master Short summarized the following principles which emerged from the rules and previous jurisprudence:
(a) if information is sent to an expert, then the same information should be sent to the opposing party to allow that party to test the expert’s opinion;
(b) an opposing party is entitled to the facts on which the expert‘s opinion is based;
(c) so long as an expert read a document sent to him or her, then that document was considered, such that it is a ”finding” that must be produced;
(d) the privilege claimed over a document sent to an expert is waived at the time that it was decided to rely on that expert’s opinion or in circumstances where privilege is waived over the report, even if the waiver was inadvertent;
(e) by sending a defence medical assessor portions of surveillance, privilege over the full surveillance video or all
photographs is waived.
Master Short found it was not appropriate for a non-party (medical assessor) to have access to relevant documents before the injured party has been granted equivalent access. Privilege is lost at the point the report is sent to the expert.
He ordered the defendant to produce a copy of the surveillance (including written reports, photos, video or other electronic records) to the plaintiff, if it is provided to the defence medical assessor.