Recent Federal Court decisions suggest that the prosecution history of Canadian patents may not be completely irrelevant. The Supreme Court of Canada in Free World Trust v. Electro Sante Inc. in 2000 wrote that the use of file wrapper estoppel was emphatically rejected in Lovell Manuafacturing Co. v. Beatty Bros. Ltd. and has been generally excluded over the years for the purpose of construing the claims.1 The prosecution history of a patent is inadmissible for the purpose of construing the patent claims, the reason being that extrinsic evidence is not permissible for the purposes of construction.2 The prosecution history constitutes extrinsic evidence:
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 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 note 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.3
The Court has noted that the reason for refusing extrinsic evidence is that such evidence would render patent construction even more difficult than it already is.4
However, in a 2013 decision in a patent infringement case, the Court was considering an argument relating to the essential nature of a claim element. During prosecution of the patent, claims were rejected in the face of prior art, and elements were added to the claims in order to overcome the rejection. The argument was made that there was no clearer indication that the element was essential than this addition to overcome the rejection.5 The Court found as follows:
While statements or admissions made in the course of patent prosecution shall not be used for the purpose of interpreting a claim, this is not what the Court is called upon to do in the case at bar. A change in the wording of a claim as a result of an objection from the Patent Office is an objective fact from which an inference may be drawn, and is not the same as representations made to the Patent Office. A purposive construction should obviously focus on the wording of a claim, obviously, but this is a far cry from saying that nothing else should be considered.6
The reasoning applied in Distrimedic was recently relied upon in the context of considering essential elements of a claim.7
It should be remembered that the Court has held in the past in a decision that was cited by the Supreme Court of Canada in Free World that information in file wrappers "may be relevant for some purposes on some occasions".8 It remains to be seen for what purposes and on which occasions, if any, Canadian Courts will find file wrappers to be relevant. In any event, it may be prudent to expect to see more arguments relating to file wrappers in the future as parties and the Court continue to explore their possible use in litigation.
Footnotes
1. Free World Trust v. Electro Sante Inc., [2000] 2 S.C.R. 1024 at 1060-1061 [hereinafter Free World].
2. Free World, ibid. See also Merck & Co. Inc. v. Apotex Inc. (2006), 53 C.P.R. (4th) 1 at para. 119 (F.C.); varied on different grounds, 2006 FCA 323; leave to appeal to SCC refused, [2006] S.C.C.A. No. 507 [hereinfter Merck].
3. Free World Trust, ibid.
4. Merck, supra note 2.
5. Distrimedic Inc. v. Dispill Inc. et al., 2013 FC 1043 at para. 207 [hereinafter Distrimedic].
6. Distrimedic at para. 210.
7. Eli Lilly Canada Inc. v. Mylan Pharmaceuticals ULC, 2015 FC 125 at para. 154.
8. Foseco Trading Ag v. Canadian Ferro Hot Metal Specialties Ltd. (1991), 36 C.P.R. (3d) 35 at 47 (F.C.T.D.), cited in Free World at para. 67.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
