Whether south or north of the US-Canada border, the proper standard of review of patent claim construction sometimes, especially in complex cases, can be problematic. South of the border, a recent decision of the Supreme Court of the United States signals a growing acceptance that deference should be accorded to the interpretation of patents reached by those who have seen experts and evaluated them: Teva Pharmaceuticals USA v Sandoz, 574 US __ (2015).This observation was also made, north of the border, in a recent appeal to the Canadian Federal Court of Appeal. In Cobalt Pharmaceuticals Company v Bayer, 2015 FCA 116, the Court of Appeal considered the standard of review on claim construction. The Court acknowledged that, as the law currently stands in Canada, claim construction is to be reviewed on a standard of correctness as it is a question of law (and so no deference is given to the lower court’s construction). The assessment of expert evidence on a matter of fact is reviewed on a deferential standard (meaning the assessment by the lower court is overturned only if it contains a palpable and overriding error).

However, the Court of Appeal further noted in passing that, “Often the experts’ testimony stretches beyond opinion evidence and goes into factual matters within their knowledge that are relevant to the construction exercise”. The Court asked, “Can appellate judges really second-guess the trial judge, who, often over many days, has been educated in the relevant art and has seen and evaluated the experts? Who are the appellate judges to review on the basis of correctness, stepping into the shoes of the trial judge and imposing their own views of the matter?”

As noted by the Supreme Court of Canada, the inventor is addressing others in the same line of work. However, words have layers of significance and secondary meanings. The word “bench”, for example, means a physical object to weight-lifters but has numerous secondary meanings for members of the legal profession.

The Court of Appeal suggested that claim construction cannot reasonably be a “pure” question of law that is reviewable on a non-deferential standard – except for an extricable legal question, which is reviewed for correctness. Rather, the Court suggested that interpretations of the specification should be reviewed on a deferential standard when they are heavily dependent on expert testimony.

The Court of Appeal invited the Supreme Court of Canada to provide guidance on the standard of review on claim construction. Leave to appeal to the Supreme Court of Canada was not sought though. However, the Cobalt decision leaves the door open. In future cases where claim construction is disputed, parties may seize the opportunity to ask the Supreme Court to revisit the issue of standard of review on claim construction.