In a move that surprised many in the IP community, a budget bill that received royal assent before the holidays, introduced file wrapper estoppel to Canadian patent law.
Bill C-86 (link) included a number of changes to intellectual property legislation including enacting the College of Patent Agents and Trade-mark Agents Act, reforming the Copyright Board, and numerous amendments to the Patent Act, Trade-marks Act and Copyright Act.
One of the changes to the Patent Act, allows for the patent file wrapper or file history to be used to rebut claim construction of a patent. The file wrapper refers to the correspondence back and for the between the patent office and a patent applicant that includes arguments as to why a patent should be granted and any amendments to the patent application.
New section 53.1(1) of the Patent Act, reads as follows. Subsections (2) and (3) relate to divisional and re-issued patents and a new section 123.1 relates to Certificates of Supplementary Protection.
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.
The use of the file wrapper to help define the scope of the claims of a patent is well established in the United States. The US Supreme Court summarized this doctrine as “a rule of patent construction, consistently observed, that a claim in a patent as allowed must be read and interpreted with reference to claims that have been cancelled or rejected, and the claims allowed cannot, by construction, be read to cover what was thus eliminated from the patent.” (Schriber-Schroth Co. v. Cleveland Trust Co., 311 U.S. 211 (1940)). This rule is primarily applied when considering what equivalent features, a “doctrine of equivalents”, may be included within the meaning of a claim term. The doctrine of equivalence is not a concept that has a direct parallel in Canadian patent law.
In Canada, the settled law had been that the file wrapper was not to be considered for the purpose of patent claim construction. The Supreme Court of Canada stated (Free World Trust v. Électro Santé Inc.,  2 SCR 1024),
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.
I earlier wrote about other uses of the file history that litigants were putting before the court, or at least trying to put before the court (see Is File History Estoppel Coming to Canada?). In 2016, Justice Locke discussed, in Pollard Banknote Limited v. BABN Technologies Corp., 2016 FC 883, a case I was involved in, how file wrapper estoppel may have applied in that case, if it was applicable to claim construction. He noted that, “for now Canadian law appears quite settled that extrinsic evidence is not relevant to claim construction”:
I would expect that SG’s argument would never have made it to a trial in the US where the principle of file wrapper estoppel applies. There, SG would likely not have been allowed to argue a claim construction that attempts to recapture ground conceded during prosecution of the patent application to avoid prior art.
This case highlights a potential risk in taking a simpler approach to claim construction by ignoring extrinsic evidence, such as the prosecution history of the patent in suit. As revealed in my analysis above, excluding such extrinsic evidence resulted in a very different construction of the phrase “a removable continuous scratch-off coating covering both the printed indicia in said play area and the bar code” than would otherwise have been the case.
In the UK, the Supreme Court in 2017 released its decision in Actavis UK Ltd v Eli Lilly & Co  UKSC 48 which allowed for variants in claim construction. The decision also discussed how the patent file history may be considered when analyzing potential variants. Lord Neuberger wrote (at paragraph 88),
While it would be arrogant to exclude the existence of any other circumstances, my current view is that reference to the file would only be appropriate where (i) the point at issue is truly unclear if one confines oneself to the specification and claims of the patent, and the contents of the file unambiguously resolve the point, or (ii) it would be contrary to the public interest for the contents of the file to be ignored. The first type of circumstance is, I hope, self-explanatory; the second would be exemplified by a case where the patentee had made it clear to the EPO that he was not seeking to contend that his patent, if granted, would extend its scope to the sort of variant which he now claims infringes.
With the legislative change to claim construction now in force in Canada, and applicable to currently pending litigation, as well as any new litigation, it will be interesting to see how judges apply this new section to allow “evidence to rebut any representation” made by the patentee. Sections 53.1 and 123.1 “apply in respect of any action or proceeding that has not been finally disposed of on the coming into force of that section 53.1” on December 13, 2018.
Judges will likely be asked to consider US and UK precedents as to how the patent file history may be applied, and the scope of considering the file history for claim construction, particularly as the new section appears directed to use by a defendant to “rebut any representation made by a patentee” rather than as a general aid in claim construction.