Answer ... Claims construction is antecedent to consideration of both validity and infringement issues. Generally, claims construction is done by the court in infringement proceedings at trial or on a motion for summary judgment when the court finds the case suitable for disposition on a summary basis, and not in a preliminary hearing dedicated solely to claims construction.

Answer ... The meaning of claim terms is determined in accordance with principles of purposive construction: the claims language must read in an informed and purposive way (Free World Trust v Électro Santé Inc, 2000 SCC 66). On such a purposive construction, the claims language will show that some elements are essential, while others are non-essential. Claim elements are presumed to be essential and the party alleging that an element is non-essential bears the onus of so establishing.

The determination of whether elements of a claim are essential or non-essential is made on the basis of the common knowledge of the worker skilled in the art to which the patent relates, as of the date the patent is published. An element is essential if it is required for the invention to work as intended. An element is also essential if that is the inventor’s intent, as expressed in or inferred from the claims, regardless of the element’s practical effect on the working of the invention. An element is non-essential if it was obvious to the skilled reader at the relevant time that the element could be substituted or omitted without affecting the working of the invention.

While the claim language is paramount, the context of the specification as a whole is also taken into account.

Answer ... File wrapper: Historically, patent claim construction was based on the patent specification itself without resort to extrinsic evidence. However, the Patent Act now explicitly permits communications between the patent owner and the Canadian Intellectual Property Office to be admitted into evidence to rebut representations made by the patent owner in a proceeding relating to claim construction. Other extrinsic evidence, such as other patents or inventor testimony, continues to be generally inadmissible when construing patent claims.

Expert witnesses: Patent construction is a matter of law for the judge. Expert evidence is necessary only where the meaning of a term is not apparent based on a reading of the patent specification.

Claim terms are to be interpreted from the perspective of a person of ordinary skill in the art. The testimony of expert witnesses is often used to help establish common knowledge of persons skilled in the relevant art at the relevant time and inform the meaning of claim terms.

Experts should be sufficiently knowledgeable of the art to which the patent relates to understand the nature and description of the invention on a technical level.

Specification: Where ambiguity exists in the language of the claims, recourse to the disclosure portion of the specification is permissible.

Other claims: A limitation in a dependent claim can be used to evidence that the corresponding independent claim need not have this feature, as otherwise the dependent claim would have been redundant.