Canadian Court Ponders Role Of Prosecution History In Claim Construction

Under Canadian Patent law, there is a rule against using the prosecution history to construe a claim of a patent. This rule stands in stark contrast to the situation in the United States where amendments and arguments before the United States Patent and Trademark Office (USPTO) may serve to limit the scope of a claim.

However, in the past few years, at least two decisions by the Federal Court of Canada have commented on this principle. These decisions have introduced some uncertainty into the issue of whether a patentee enforcing a Canadian patent should be concerned about the consequences of representations and amendments made before the Canadian Intellectual Property Office (CIPO) during the prosecution of a patent application.


The modern basis for disregarding the file wrapper while construing the claims of a Canadian patent was established by the Supreme Court of Canada in Free World Trust v Électro Santé Inc, 2000 SCC 66. At paragraph 66 of this decision, Justice Binnie explains that it is the inventor's intention, as informed by the language of the claims, that determines the proper construction of a claim:

In my view, those references to the inventor's intention refer to an objective manifestation of that intent in the patent claims, as interpreted by the person skilled in the art, and do not contemplate extrinsic evidence such as statements or admissions made in the course of patent prosecution. To allow such extrinsic evidence for the purpose of defining the monopoly would undermine the public notice function of the claims, and increase uncertainty as well as fuelling the already overheated engines of patent litigation. The current emphasis on purposive construction, which keeps the focus on the language of the claims, seems also to be inconsistent with opening the pandora's box of file wrapper estoppel.

Pollard Banknote Ltd v BABN Technologies Corp and Scientific Games ULC, 2016 FC 883

On July 28, 2016, Justice Locke of the Federal Court of Canada issued a decision that analyzed this passage from Free World Trust in view of what was perceived to be a party's submission to the Court that was "entirely opposite to the position [taken] before the Examiner in order to obtain allowance" of the patent.

Briefly, an issue in this invalidity and infringement proceeding was the meaning of the word "continuous" in Canadian Patent No. 2,752,551 (the '551 patent) to describe a lottery ticket with "a removable continuous scratch-off...

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