The Federal Court recently released the first decision in which the scope of Section 53.1 of the Patent Act – the so-called 'file wrapper estoppel' provision – has been considered.

In Canmar Foods Ltd v TA Foods Ltd (2019 FC 1233), the court held that representations made by a patentee during prosecution of a foreign patent application constituted admissible evidence under Section 53.1. The court recognised that Section 53.1 specifies using only Canadian prosecution file histories to rebut positions taken on claim construction and makes no reference to prosecution histories from other jurisdictions. Notwithstanding this, the court found that it could consider the US application prosecution history as part of a purposive construction of the claims at issue based on the "extraordinary circumstances" identified by the court in the case.

Claim construction issues

In Canmar Foods the defendant, TA Foods Ltd, brought a motion for summary judgment based on non-infringement of the asserted claims of Canadian Patent 2,582,376 (the '376 patent), entitled "Methods for Roasting Oil Seed, and Roasted Oil Seed Products".

Specifically, the defendant argued that its allegedly infringing oil seed roasting or cooking process fell outside the claims of the '376 patent because it did not heat oil seed in a "stream of air" and did not maintain the oil seed in an "insulated roasting chamber or tower", as required by independent Claim 1.

In support of the motion, the defendant relied on the Canadian prosecution history and the prosecution history of the corresponding US Application 11/576,405 filed before the US Patent and Trademark Office (USPTO). The defendant argued that the stream of air and insulated roasting chamber or tower limitations had been added to overcome prior art cited by the USPTO. Further, it contended that the applicant had adopted those same limitations in the '376 patent Canadian prosecution history in order to overcome novelty and obviousness objections raised by the Canadian examiner.

Scope of Section 53.1

In rendering its judgment, the court had to assess whether the scope of the new Section 53.1 of the Patent Act permits the admissibility into evidence of foreign prosecution histories.

The court noted that Section 53.1 makes no reference to prosecution histories from other jurisdictions. Accordingly, absent extraordinary circumstances, representations made by a patentee during the prosecution of a foreign patent application should remain inadmissible for the purposes of construing Canadian patent claims. However, the court held that such extraordinary circumstances existed in the present case:

Extraordinary circumstances arise where, as in this case, the patentee acknowledges that the claims have been amended to be substantially the same as claims submitted in another jurisdiction, and the patentee admits that the amendments have limited the scope of the claims in order to make the claims novel and non-obvious. In these circumstances, the Court should be able to refer to the foreign prosecution history for the limited purpose of purposively construing the Canadian Claims.

The court suggested that ignoring the reference to the US prosecution history and the restrictions made to claims to overcome novelty and obviousness objections that were then incorporated into the Canadian claims during prosecution would undermine the intent and effect of Section 53.1.

Impact on summary judgment

Ultimately, the court granted summary judgment to the defendant based on the court's construction of the asserted claims and its finding that the defendant's flax roasting process did not include heating oil seed in a stream of air and an insulated roasting chamber or tower. The court determined that these elements were essential, based at least in part on the foreign prosecution history evidence submitted by the defendant. However, the court also held that the defendant's process could not constitute heating the oil seed in a stream of air, regardless of the foreign prosecution history. In this respect, the court's finding on admissibility of the foreign prosecution history might be argued to be obiter.

Canmar Foods is also noteworthy as a rare example of a court granting summary judgment in a patent infringement action in Canada. In previous cases, the courts have been hesitant to grant summary judgment since most claim construction and infringement and validity analyses require expert evidence and resolution of credibility issues. In the present case, the court found that no expert evidence was required to purposively construe the claims.


The first judicial interpretation of Section 53.1 in Canmar Foods suggests that, notwithstanding the clear language of the provision, foreign prosecution histories may be admissible for the purposes of claim construction in certain extraordinary circumstances. The court in Canmar Foods found that the patentee had specifically referred to the claims submitted to the USPTO and admitted that the amendments to claims in the Canadian patent had limited the scope of the claims in order to make them novel and non-obvious.

The plaintiff may appeal this decision, as of right.

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