Interpreting Claims In Canadian Patent Law: Purposive Construction And "Essential" Elements

• Published date: 15 December 2022
• Subject Matter: Intellectual Property, Patent
• Law Firm: MLT Aikins LLP
• Author: Mr Gregory Forrest and Adam Lakusta

In Canada, the anatomy of a patent (also known as the specification) consists of four parts: the abstract, the claims, the description and the drawings. Legally and commercially, the most important element is the claims - and a recent court decision has affirmed a long-standing approach on how to interpret patent claims.

The recently decided Benjamin Moore & Co. v Canada (Attorney General), 2022 FC 923 ("Benjamin Moore") further affirmed the two highly influential decisions commenting on claims construction in Free World Trust c Électro Santé Inc, 2000 SCC 66 ("Free World Trust") and Whirlpool Corp. v Camco Inc., 2000 SCC 67 ("Whirlpool"). These decisions emphasized the importance of "purposive construction" and interpreting claims with reference to their "essential" elements.

In Benjamin Moore, the Court pointedly rejected the "problem-solution" approach taken by the Canadian Intellectual Property Office wherein problems disclosed in patent applications were identified and the claims were construed in accordance with what elements would be essential to solving the identified problem.

In Whirlpool, the SCC described purposive construction as the "identification by the Court with the assistance of the skilled reader, of the particular words or phrases in the claims that describe what the inventor considered to be the 'essential' elements of his invention." As stated in Free World Trust, it would be unfair to allow copycat inventions to elude patent monopolies simply because a competitor switched some of the "bells and whistles" from a patented invention.

Determining Whether an Element Is "Essential"

Whether an element is "essential" is a key consideration in any patent infringement dispute. If an allegedly infringing product or service contains an element deemed to be essential in a patented invention, it will be found to infringe the patent. However, if a product or service is found to contain only non-essential elements of the patent, then the product or service has not infringed the patent.

To determine the "essential" elements of claims, the Supreme Court held that it is necessary to construe a patent as a whole, considering the entire anatomy of the patent, including the description. Furthermore, the Court held that claims construction should be determined from the point of view of a person skilled in the "art" of the particular field of invention (the "POSITA"). In most cases, claims construction is achieved by the courts with the assistance of...