Section 53.1 of the Patent Act
Section 53.1 of the Patent Act came into force on 30 October 2019 and contemplates the introduction of a patent’s prosecution history during claims construction. The relevant portion of the provision states:
Admissible in evidence
53.1 (1) In any action or proceeding respecting a patent, a written communication, or any part of such a communication, may be admitted into evidence to rebut any representation made by the patentee in the action or proceeding as to the construction of a claim in the patent if
(a) it is prepared in respect of
(i) the prosecution of the application for the patent,
(ii) a disclaimer made in respect of the patent, or
(iii) a request for re-examination, or a re-examination proceeding, in respect of the patent; and
(b) it is between
(i) the applicant for the patent or the patentee; and
(ii) the Commissioner, an officer or employee of the Patent Office or a member of a re-examination board.
This provision thus reverses longstanding Canadian jurisprudence rejecting the introduction of such extrinsic evidence in claims construction.
While a plain reading of the provision suggests that only the Canadian prosecution history is admissible and that it may only be introduced to rebut specific representations made by the patentee, the scope of the provision was unknown upon its enactment. Additionally, other jurisdictions like the United States have framed the use of prosecution history as “file wrapper estoppel”, whereby a patentee is blocked from recovering subject matter ceded via narrowing amendments to patent claims made during the prosecution of a patent. Whether Canadian courts would interpret Section 53.1 similarly was also unknown.
The Federal Court has now provided its judicial interpretation of Section 53.1 in three decisions and the scope of the provision has started to solidify. These decisions consider when recourse to the prosecution history is permissible and for what purpose, and whether foreign (i.e. non-Canadian) prosecution history is admissible.
Use of prosecution history is integrated in the claims construction process
In Bauer Hockey Ltd. v. Sport Maska Inc. (CCM Hockey) 2020 FC 624 [Bauer], the Court held that there are no requirements before considering prosecution history under Section 53.1. Grammond J stated that unlike in the United States where the use of prosecution history is described in terms of estoppel, section 53.1 expressly considers it in the context of claims construction. Further, he reasoned that since a patentee is always making representations to the court during patent litigation, reference to the prosecution history is “simply integrated in the interpretive process” of claims construction.
In this decision, the Court stated in its conclusion that the “interpretation put forward by [Bauer’s expert witness] is at odds with the language of the claims, seeks to ascribe a purpose that is not mentioned in the patent and cannot be reconciled with the prosecution history”. Therefore, the Court indeed considered the prosecution history of the patent at issue, but it was not solely determinative in its claims construction analysis.
Foreign prosecution history is generally inadmissible
The issue of the admissibility of foreign prosecution history arose in Canmar Foods Ltd v TA Foods Ltd 2019 FC 1233 [Canmar] and Gemak v Jempak 2020 FC 644 [Gemak]. Both decisions generally interpreted section 53.1 as not substantially changing the existing state of Canadian patent law, which excludes the introduction of foreign prosecution history. However, in Canmar, a limited exception to this rule was contemplated.
In Canmar, the defendant argued that the US prosecution history of the patent at issue was admissible under section 53.1. Specifically, it was argued that the US prosecution history was admissible since the plaintiff had acknowledged in communications respecting its Canadian application that certain claims were amended to mirror those in its corresponding US application to overcome objections made by the US patent office. Manson J stated that under “extraordinary circumstances”, such as when foreign prosecution history has been made part of the Canadian prosecution history, it may be admissible under section 53.1. He further considered that the facts of this case constituted such circumstances.
However, the US prosecution history was not determinative in Canmar, as the Court held that “[r]egardless of the US Application prosecution history… the Defendant does not infringe the claims of the [patent at issue]”. At least one commentator has considered that Manson J’s holding is thus obiter because the decision does not hinge on the US prosecution history, and further highlights that the US prosecution history is not actually referred to directly in the reasons.
Gemak also involved a defendant seeking to introduce the US prosecution history of the patent at issue in an infringement proceeding. Here, the Court found that section 53.1 was not triggered and that foreign prosecution history was inadmissible on the basis of statutory interpretation of section 53.1 and previous jurisprudence barring the introduction of foreign prosecution history. Interestingly, Lafrenière J did not address Manson J’s holding in Canmar in this decision. However, it should be noted that the facts in this case may be distinguishable from Canmar because the plaintiff does not appear to have expressly acknowledged that a claim its Canadian application was amended to mirror that of a foreign application.
Practical considerations for patentees
In view of the decisions above, patentees and their patent agents should expect that the entire Canadian prosecution history of a patent will likely be considered under section 53.1 when courts construe patent claims. Increased care will thus be required during patent prosecution because it is less likely a patentee will regain ground ceded in the prosecution process.
Since there is some uncertainty at the Federal Court regarding the admissibility of foreign prosecution history where it is introduced as part of the Canadian prosecution history, the extent to which such prosecution history is admissible remains unclear. Therefore, it is likely prudent for patentees to be wary of expressly referring to foreign prosecution history, like in Canmar, while prosecuting a Canadian patent application.
Authors: Leslie J. Chan and Dana Turner-Ryan
 The prosecution history of a patent is known as its “file wrapper” in the United States.
 Bauer at para 65.
 Bauer at para 113.
 Canmar at para 61 and para 70.
 Canmar at para 77.
 Canmar at para 70.
 Canmar at para 79.
 Sufficient Description, “Foreign Prosecution History Admissible under S 53.1 — or Is It?” 22 October 2019. [Online]. Available: http://www.sufficientdescription.com/2019/10/foreign-prosecution-history-admissible.html
 Gemak at paras 79-86.
 Gemak at paras 66-71.