Federal Court of Appeal Cautions Against Use of Foreign Prosecution History
January 27, 2021
By Andrew McIntosh and Shuo Xing
On January 20, 2021, the Federal Court of Appeal issued its much awaited decision in Canmar Foods Ltd v TA Foods Ltd, 2021 FCA 7 (“Canmar FCA”). Canmar FCA is an appeal from a summary judgment motion (2019 FC 1233) (“Canmar FC”) dismissing a patent infringement action brought by Canmar Foods with respect to its patent CA 2,582,376 (the 376 Patent). In Canmar FC, the Federal Court considered the first application of s. 53.1 of the Patent Act regarding the admissibility of prosecution history to construe the patent’s claims since the section’s coming into force in late 2018 (read our article here). The Court of Appeal upheld the dismissal of the infringement action but held that the Federal Court judge should not have considered statements made by the patentee to the United States Patent Office to construe the patent’s claims. However, the Court of Appeal refrained from deciding whether statements made during prosecution of a foreign application could ever be considered for the purposes of claim construction.
Historically, communications between a patent applicant or patentee and the Canadian Patent Office during the prosecution of a patent application were not later admissible in evidence to construe a patent’s claims.1 However, this position was subject to much criticism, and in 2018 the Patent Act was amended to introduce s. 53.1. This section allows written communications between the patentee and the Patent Office to be admitted into evidence in certain limited circumstances to rebut representations made by the patentee in litigation regarding claim construction. In Canmar FC, the Court held that while ordinarily only Canadian prosecution history is admissible for claim construction, foreign prosecution history may also be admissible under extraordinary circumstances.2 In holding that “extraordinary circumstances” existed in this case, the Federal Court pointed to the patentee’s acknowledgment during prosecution that the claims in the then 376 application were amended to conform to the claims in the corresponding US patent application to overcome novelty and obviousness rejections.
On appeal, Canmar argued that the trial judge erred in considering the prosecution history of a foreign patent application when construing the 376 Patent. Specifically, Canmar submitted that the trial judge erred in expanding the scope of s. 53.1, and in effectively introducing the American doctrine of incorporation by reference (where an external document is cited in such a manner that it becomes part of the host document).
After reviewing the history of file wrapper estoppel in Canada, the US and the UK, the Court of Appeal reiterated that while a strict reading of s. 53.1 does not sanction the use of prosecution file as an independent, stand-alone aid to construction of a patent claim, it can still be used along with the claims and the disclosure to construe a claim to the extent that it may rebut a patentee’s representation.3 However, the Court of Appeal cautioned that “courts should be wary to extend the detailed language of section 53.1, which is specific about the communications being limited to those with the Canadian Patent Office”, and that it would be “against statutory interpretation principles to try to go beyond [the legislation’s] original intent”.4 Further, it was noted that admitting foreign file wrapper might cause overly contentious and expensive litigation, especially since different jurisdictions have different patent registration processes and standards, and use different language in patent claims.5
Regarding the doctrine of incorporation by reference, the Court of Appeal was not willing to decide whether it should formally apply as an exception to the general prohibition of foreign prosecution files. However, the Court held that on the facts of this case, the Federal Court judge should not have considered the US prosecution history because nothing in the Canadian file identified with any detailed particularity what specific “written communication” from the US prosecution is incorporated or where it could be found. This seems to suggest even if incorporation by reference should allow courts to consider foreign file wrapper, a detailed reference to a specific written communication in the foreign file wrapper would be required.
While the Canmar FCA decision provides some comfort to patent applicants that general statements made to the Canadian Patent Office about corresponding foreign applications should not be readily admissible in later litigation, it remains unresolved whether this is true in all circumstances. For instance, while Canmar FC made specific reference to the Patent Prosecution Highway program commonly used to expedite patent examination as one possible situation for considering foreign prosecution history, the Court of Appeal did not address the issue. Accordingly, patent applicants should continue to exercise caution when submitting arguments to the Canadian Patent Office until there is more clarity surrounding this point.
1 See for example Free World Trust v Électro-Santé Inc,  2 SCR 1024.
2 Canmar Foods Ltd v TA Foods Ltd, 2019 FC 1233 (Canmar FC) at paras 62 and 74.
3 Canmar Foods Ltd v TA Foods Ltd, 2021 FCA 7 (Canmar FCA) at para 64.
4 Canmar FCA at para 70.
5 Canmar FCA at paras 70 and 71.
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