On Sept. 25, 2019, the Federal Court of Canada released its first decision interpreting the scope of new section 53.1 of the Patent Act. This statutory provision allows for the patent "file wrapper" or file history - chiefly comprising correspondence between a patentee and a patent office during prosecution - to be used to rebut a patentee's representations about patent claim construction.

At issue in the case were the circumstances under which the new provision applies to file wrappers of patents filed in foreign jurisdictions - as well as those in Canada.

As we outline below, the Court's ruling underscores the heightened importance under Canada's new patent regime of adopting a strategic approach to patent office communications during the prosecution phase. Equally, it should serve to give prospective patentees pause when deciding to leverage the results of a foreign patent application to expedite a Canadian application.

In Canmar Foods Ltd. v TA Foods Ltd., 2019 FC 1233, a decision concerning a motion by defendant TA Foods Ltd. for summary judgment, Justice Manson discussed the scope of admissibility under section 53.1 in respect particularly to foreign prosecution histories.

Justice Manson held that the language of section 53.1 is limited to communications between the patentee and the Canadian Patent Office, and generally should be applied in that context.  However, recognizing that purposive construction requires consideration of not only the claims and the disclosure, but also the substance behind intentional amendments, it was held that "[i]gnoring the reference to United States prosecution history and the restrictions made to claims to overcome novelty and obviousness rejections that were incorporated into the Canadian claims during prosecution would emasculate the intent and effect of section 53.1" (para. [71]). 

To avoid the opening of the proverbial "pandora's box," Justice Manson was cautious in limiting the foreign applicability of section 53.1 to allow for consideration of foreign prosecution histories only in extraordinary circumstances that are consistent with the realities of patent prosecution in Canada.  As indicated in paragraph 74 of the decision:  "Extraordinary circumstances arise where, as in this case, the patentee acknowledges that the claims have been amended to be substantially the same as claims submitted in another jurisdiction, and the patentee admits that the amendments have limited the scope of the claims in order to make the claims novel and non-obvious".  This interpretation recognizes the intended effect of section 53.1 of the Patent Act (para. [77]).