Federal Court of Appeal Provides Clarity on File Wrapper Estoppel

On January 20, 2021, the Federal Court of Appeal (FCA) dismissed the appeal in Canmar Foods Ltd. v. TA Foods Ltd., 2021 FCA 7.  This was an appeal of the first court decision (previously reported in the E-TIPS® Newsletter here) to interpret the file wrapper estoppel provision, s. 53.1 of the Patent Act, recently introduced into Canadian law.  The FCA decision provides us with some more clarity on how this provision should be interpreted.

Extent and Purpose For Which Prosecution History Can Be Introduced

In its discussion of file wrapper estoppel, the FCA noted that a number of lower court decisions disagreed as to the extent and purpose for which prosecution history can be introduced into evidence during litigation.  While certain lower court cases held that use of the prosecution history is limited to the rebuttal of identifiable representations made by a patentee as to claim construction, another decision held that the prosecution history is admissible whenever the issue is one of claim construction. 

The FCA chose not to resolve the issue at this time.  The FCA did, however, note in obiter that a strict reading of s. 53.1 does not sanction the use of the prosecution history as an independent, stand-alone aid to claim construction.  Nonetheless, the prosecution history does play a role in construing claims, along with the claims themselves and disclosure, to the extent that it may rebut a patentee’s representation.

Consideration of Foreign Prosecution History

The FCA also considered the appealed decision’s commentary on foreign prosecution history.  In the appealed decision, the lower court held that while s. 53.1 limits the communications that can be admitted into evidence to those between the patentee and the Canadian Patent Office, the court is allowed to look at foreign prosecution history in “extraordinary circumstances.”  The lower court held that extraordinary circumstances were present in the case at hand, where during Canadian prosecution the patentee specifically referred to the corresponding US Application’s prosecution history and acknowledged that the amendments made to the Canadian claims were made to overcome novelty and obviousness concerns raised in the US. 

The FCA held that courts should be wary to extend the language of s. 53.1, which is specific about the admissible communications being limited to those with the Canadian Patent Office.  While the FCA declined to express a view on whether the prosecution history of a foreign application can ever be considered pursuant to s. 53.1, in this case, the FCA held that the lower court should have refrained from doing so.  Here, the office action response at issue merely stated that the new claims on file “correspond substantially to those submitted during prosecution of a related United States application.”  The FCA took the position that it would be a stretch to say that the prosecution of the US Application was incorporated by reference when the specific application was not even cited in the response.

Summary By: Vanessa Komarnicki