“Consisting essentially of” in Canadian Claim Construction

Due to the flexible nature of the law of claims construction in Canada, the meaning of the commonly used transitional phrase "consisting essentially of" may surprise foreign lawyers and patent practitioners. As a result, when drafting patent applications that may be destined for Canada, consideration should be given to avoiding this term whenever possible.

The use of the phrase "consisting essentially of" in patent claims is common in other jurisdictions, particularly the United States. Patent practitioners in these jurisdictions often assume that this term would have the same meaning in Canada as in their jurisdictions. In the US, the phrase limits the scope of a claim to the specified materials or steps “and those that do not materially affect the basic and novel characteristic(s)” of the claimed invention.[1] In Europe, the phrase has been held to mean that "specific further components can be present, namely those not materially affecting the essential characteristics" of the specified materials or steps.[2] However, this phrase may not have these meanings in Canada.

In the Canadian Intellectual Property Office Manual of Patent Office Practice, "consisting essentially of" is listed with "consisting of,"[3] a term well-established to limit the scope of the claim to the specified materials or steps. The proximity of these two transitional phrases in the Manual appears to suggest that the former phrase has a meaning that is close to the meaning of the latter. However, the Patent Appeal Board has variously interpreted "consisting essentially of" to mean "comprising,"[4]^,[5] to exclude materials or steps not specified in the claim,[6] or to have a meaning similar to that in the US or Europe.[7]

Courts in Canada have also interpreted the term flexibly. The Federal Court has rejected the US interpretation.[8] In a recent decision, the Federal Court interpreted "consisting essentially of" to exclude materials and steps not specified in the claim.[9] However, in another decision, the Federal Court construed a claim directed to "[a]n abridged … composition" and determined that "consisting essentially of" included other materials and steps not specified in the claim, in view of the description, another dependent claim, and the presence of the word "abridged" in the preamble of the claim.[10] Notwithstanding the apparent discrepancy, both decisions stated that, in line with the Supreme Court of Canada’s pronouncement on claim construction in Free World Trust,[11] the claims at issue should be purposively construed and the whole disclosure must be considered.

Thus, in Canada, the phrase "consisting essentially of" is not likely to have the established meanings it does in the US and Europe. Rather, it will be interpreted having regard to the whole disclosure of the particular specification. Therefore, foreign patent practitioners who use the term in their drafting of patent claims may be in for a surprise when the claims are eventually construed by the Patent Appeal Board or a court in Canada. To avoid such surprises, a more specific term should be used.

ABOUT THE AUTHORS

Lei Gao and Andrew Kaikai are Associates at Ridout & Maybee LLP.