Federal Court Opens Door to use of Foreign Patent Prosecution Histories in Canadian Litigation

October 24, 2019

Patent owners should know how communications with the Patent Office (in Canada and abroad) can affect the scope of their patent rights.  Historically these communications were inadmissible in Canadian patent proceedings; but this changed last year with the introduction of section 53.1 of the Patent Act.  The Federal Court has now considered the scope of this new section. 


A well-established principle in Canadian patent law is that the claims of a patent are to be construed without regard to extrinsic evidence.  As such, prosecution histories (correspondence between the patentee and the patent office during the prosecution of a patent application) were historically held to be inadmissible for this purpose.  This has been a key distinction between patent law in Canada and in the United States, where prosecution histories are routinely considered under the doctrine of prosecution history or “file wrapper” estoppel.

Late last year, the Canadian Patent Act was amended to introduce an exception to this well-established principle:  the new section 53.1 provides that a written communication between the patentee and the Canadian Patent Office may be admitted into evidence to rebut any representation made by the patentee as to the construction of a claim in the patent. 

The Federal Court’s recent decision in Canmar Foods Ltd. v. TA Foods Ltd. (“Canmar”) interpreted and applied this new provision.


In Canmar, TA Foods Ltd. (“TAF”) defended a patent infringement claim by bringing a motion for summary judgment, arguing that its process did not infringe the patent in issue.

The clams of the patent were directed to a method of roasting oil seed that included heating the oil seed in “a stream of air” and transferring and maintaining the heated oil seed in “an insulated or partially insulated roasting chamber or tower”. On the motion, TAF argued that its oil seed roasting process did not infringe the claims because it did not include these two elements. 

TAF relied on both the Canadian prosecution history for the patent allegedly being infringed and the prosecution history of the corresponding US application to support its position that these two elements were essential to the invention claimed. 


In considering the scope of section 53.1, the Court noted that the express language of section 53.1 was limited to communications between the patentee and the Canadian Patent Office.  Accordingly, absent “extraordinary circumstances”, prosecution histories from foreign patent applications should remain inadmissible for the purpose of patent claim construction. 

However, the Court went on to state that “extraordinary circumstances” arise where the prosecution of the foreign application is made part of the prosecution history of the Canadian patent and is relevant to limitations made to the Canadian claims. 

Applying these principles, the Court concluded that both the Canadian and United States prosecution histories were admissible since during the Canadian prosecution the patentee specifically referenced the US application and acknowledged that the claim amendments were made to overcome concerns raised in the US.  The Court reasoned that a failure to adopt such an approach would provide an incentive to applicants to refrain from being transparent with the Canadian Patent Office and may even allow applicants to rely on co-pending foreign applications to effectively avoid any application of section 53.1.

On the issue of construction of the disputed claim elements, the Court held that expert evidence was not required to construe these elements and that the admissible prosecution histories aided in the construction.  The Court found that the amendments made to the claims during the Canadian prosecution and the statements made by the patentee to the Patent Office relating to those amendments were “clear evidence” of an express intention that each of the elements was essential.  As a result, the Court concluded that, on a purposive construction, each of the disputed elements was essential.  As the Court also found that the TAF had proven that its process did not include either of the disputed claim elements, the Court held that the patent was not infringed and granted the Defendant’s motion for summary judgment.

Key Takeaways

The potential implications of amendments and submissions made during the prosecution of a Canadian patent application, including references to corresponding foreign applications, should always be carefully considered during the patent prosecution process.  The prosecution history of a patent should also be carefully reviewed when considering the strength of a claim for infringement.   

DISCLAIMER: This publication is intended to convey general information about legal issues and developments as of the indicated date. It does not constitute legal advice and must not be treated or relied on as such. Please read our full disclaimer at www.stikeman.com/legal-notice.

Stay in Touch with Knowledge Hub