As those familiar with United States patent practice know, “file wrapper estoppel” is the use of communications with the patent office to interpret (read: narrow) the scope of the claims. It’s also well known as a reason to be exceedingly cautious in providing written and oral remarks to examiners. While this has not been a reality for Canadian patent cases, that is about to change.
The Canadian government has introduced Bill C-86, which makes substantial changes to the Canadian Patent Act.
Owners of Canadian patents should be concerned if Bill C-86 is passed in its current form as it increases possible defences to patent infringement by introducing the equivalent of file wrapper estoppel.
This Bill sweeps away many years of case law prohibiting extrinsic evidence in claims interpretation or “construction.”
The exclusion of extrinsic evidence, such as the file wrapper, was set out in the Supreme Court of Canada (SCC) decisions Whirlpool Corp. v. Camco Inc.,  2 S.C.R. 1067 and Free World Trust v. Électro Santé Inc.,  2 S.C.R. 1024 that addressed claims construction in Canada. It was argued in Whirlpool that a purposive claims construction may open the door to extrinsic evidence of intent, but the Court rejected the basis for these arguments as the lower court decisions did not go outside the four corners of the specification and properly limited themselves to the words of the claims interpreted in the context of the specification as a whole.
Free World Trust also addresses the use of file wrapper estoppel, stating at para. 66 that:
“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. If significant representations are made to the Patent Office touching the scope of the claims, the Patent Office should insist where necessary on an amendment to the claims to reflect the representation.” (emphasis added)
The newly introduced Section 53.1, however, permits a written communication (or part thereof) to be admitted into evidence to rebut any representation made by a patentee in the action as to the construction of a claim in the patent.
These written communications include communications prepared in respect of the prosecution of the application, a disclaimer, a request for re-examination or a re-examination proceeding, between the applicant and the Commissioner, officer or employee of the Patent Office or a member of a re-examination board.
Further, in Subsection 53.1(2), the prosecution of a divisional application is deemed to include the prosecution of the original application. This subsection is contrary to the concept of a divisional application being directed to a different invention, and therefore representations from the original application may not be applicable to the divisional applications. This subsection should also be of concern to applicants.
If you have any questions about the proposed file wrapper estoppel system or its potential effects, please contact one of our patent team members for advice and insight.
Note: This article is of a general nature only and is not exhaustive of all possible legal rights or remedies. In addition, laws may change over time and should be interpreted only in the context of particular circumstances such that these materials are not intended to be relied upon or taken as legal advice or opinion. Readers should consult a legal professional for specific advice in any particular situation.