Executive Summary: Key Legal and Evidentiary Issues

• McCain Foods appealed the Federal Court's construction of the term "high electric field" in its '841 Patent, arguing the lower court imposed an unduly restrictive numerical range of 2 to 200 V/cm.

• Simplot's pulsed electric field technology operates at 1,000 V/cm or more, falling outside the Federal Court's construed range, leading to a finding of non-infringement.

• The Federal Court determined that if "high electric field" were broadly construed to cover Simplot's technology, the patent claims would be invalid for exceeding the scope of the invention and lacking demonstrated utility.

• Appellate review turned on whether claim construction was a question of law (correctness standard) or mixed fact and law (palpable and overriding error standard), with the Court of Appeal applying the more deferential standard.

• Expert evidence played a central role, as the term "high electric field" had no established definition in the art of food process engineering at the date of publication.

• The appeal was dismissed with costs fixed at $30,000, affirming the lower court's finding of non-infringement in favour of Simplot.

Background of the patent dispute

McCain Foods Limited and J.R. Simplot Company and Simplot Canada (II) Limited are competitors in the French fry industry. They produce and sell frozen French fries. At the heart of this litigation is McCain's Canadian Patent No. 2,412,841, known as the '841 Patent, which claims a process for treating vegetables and fruit before cooking in order to reduce their resistance to cutting. The patented process is characterized by the application of a "high electric field" directly to the vegetables and/or fruits without preheating them. In practical terms, McCain invented and patented the process of using high electric fields to treat potatoes to make them easier to cut into strips without cooking them in the process.

The Federal Court's claim construction

The dispute centered on the meaning of the term "high electric field" as used in Claim 1 of the '841 Patent. The Federal Court, in its earlier decision (2025 FC 1078), found that a person skilled in the art of food process engineering at the date of publication of the '841 Patent would have been aware that this term had no known or established definition in the art. After an extensive analysis of common general knowledge in the areas of electric fields, and their impact on plant tissues and food processing, along with pulsed electric field treatments in food processing, the Federal Court concluded that a skilled person reading the patent at the date of publication would understand "high electric field" as used in Claim 1 to mean a field in the range of about 2 to 200 V/cm. Since Simplot uses a technology known as pulsed electric field, in the range of 1,000 V/cm or more, the Federal Court concluded that the pulsed electric field systems used by Simplot did not infringe the '841 Patent during its lifetime.

Validity considerations

The Federal Court also addressed validity as an alternative finding. It held that if the term "high electric field" were construed to cover the electric fields of the type used by Simplot, the two claims at issue would be invalid for (i) being broader than the invention made or contemplated by the inventors, and (ii) lack of demonstrated or soundly predicted utility.

McCain's arguments on appeal

McCain appealed to the Federal Court of Appeal, submitting that the Federal Court erred in construing the term "high electric field." Under a broader construction of that term, McCain argued that Simplot infringes the '841 Patent. McCain further argued that the Federal Court's failure to properly construe the term led to reviewable errors in assessing the validity of the '841 Patent. Specifically, McCain submitted that the Federal Court failed to purposively construe the term "high electric field" when it imposed a rigid numerical limit, thereby excluding pulsed electric fields. This was, in McCain's view, unduly restrictive. McCain underscored that the '841 Patent does not impose a numerical limit on the term "high electric field." McCain also argued that the Federal Court prioritized the disclosed embodiments, created artificial limitations based on its understanding of the biological mechanism in the disclosed embodiments, and misapprehended the common general knowledge in order to unduly narrow the '841 Patent's scope to a subtype of high electric field.

The standard of review debate

A key procedural question was whether the Federal Court's claim construction should be reviewed on a standard of correctness or on the more deferential standard of palpable and overriding error. The Federal Court of Appeal noted that while in theory the interpretation of a patent claim is a question of law, such claims are interpreted from the point of view of a person skilled in the art, with the effect that expert evidence is often considered in determining how such a person would have understood the terms in a claim at the date of publication. Where the interpretation of a patent claim turns on the appreciation of expert evidence as to how a skilled person would understand specific terms, the Federal Court is entitled to deference and the standard of palpable and overriding error applies. The appellate court found that the Federal Court's claim construction was based on its appreciation of the expert evidence after having considered both sides of the debate in considerable detail, and accordingly applied the palpable and overriding error standard.

The Federal Court of Appeal's analysis and ruling

The Federal Court of Appeal, in a judgment delivered from the bench at Ottawa, Ontario, on April 14, 2026, by Justices Monaghan, Heckman, and Rochester, found no palpable and overriding error in the Federal Court's construction of the term "high electric field" in Claim 1. The appellate court rejected McCain's submission that the Federal Court prioritized the disclosed embodiments or created artificial limitations, noting that the Federal Court acknowledged that a patent claim is not limited to the preferred embodiments described in the disclosure, but rightly considered that the preferred embodiments are not irrelevant and may be considered as part of purposive construction. The court also did not agree that the Federal Court discounted the alleged connection between pulsed electric fields and the application of high electric fields to extracting sugar from beets. On the contrary, the Federal Court addressed McCain's position on the language used in the disclosure and then set out in detail the three reasons why it considered that McCain's reading was not determinative of the construction issue. The appellate court was of the view that the Federal Court was entitled to find, based on the evidence before it, that a skilled person reviewing the '841 Patent would not read the reference to extracting sugar from beets in isolation from the rest of the disclosure, nor would they connect the dots back to the earlier reference to pulsed electric fields without a direct reference to pulsed electric fields or pulses. Because the construction issue was resolved against McCain, the court found it not necessary to address McCain's arguments on the issues of validity. The appeal was ultimately dismissed, with J.R. Simplot Company and Simplot Canada (II) Limited prevailing as the successful parties, and costs were fixed in the all-inclusive amount of $30,000, as agreed between the parties.