[author: Junyi Chen]

The Supreme Court of Canada in Free World Trust v Électro Santé Inc, 2000 SCC 66 rejected the use of extrinsic documents such as file wrappers (patent prosecution histories) for claim construction, on the basis that allowing such evidence would undermine the public notice function of the claims and increase uncertainty.  Hence, there is no equivalent of U.S. file wrapper estoppel in Canada.

Recently, in Pollard Banknote Limited v Scientific Games Products (Canada) ULC, 2016 FC 883, Justice Locke of the Federal Court questioned whether it was time to revisit the principle of no file wrapper estoppel for claim construction, as file wrappers, like claims, are now publicly available and hence give public notice of the contents of the prosecution history.  Nevertheless, Justice Locke re-affirmed that, at present, it is settled in Canada that file wrappers are irrelevant to claim construction and therefore, in the present case, the patentee (Scientific Games) was not estopped from presenting a claim construction that contradicted its previous submissions to the Canadian Patent Office during prosecution.  In obiter, Justice Locke noted that had this case been tried in the U.S. where the principles of file wrapper estoppel apply, Scientific Games would unlikely have been allowed to argue a claim construction that attempted to recapture grounds conceded during prosecution of the application to avoid prior art.

Justice Locke found however that Scientific Games' Canadian Patent No. 2,752,551, relating to a two-dimensional authentication barcode hidden under a scratch-off area on print instant lottery tickets, was invalid for ambiguity and obviousness; in the alternative, Pollard did not infringe the patent.  This is the first time in forty years that a claim was held invalid for ambiguity in Canada.

With respect to obviousness, Justice Locke held that a patent should not be granted to a skilled person simply making an obvious change to what was known in the art, even if that art would probably not have been located in a diligent search.  He noted that concerns regarding a diligent search may be more relevant where the obviousness allegation combines two references, neither of which is part of the common general knowledge.

In light of Justice Locke's comments on revisiting the principle of no file wrapper estoppel, applicants would be advised to limit their representations and amendments before the Canadian Patent Office only to the extent necessary to overcome examiners' objections.  It would also be advisable for a party assessing the merits of a Canadian patent, to review the file wrapper for potentially problematic representations and amendments made during prosecution.

Dr. Chen is an associate with Deeth Williams Wall.