Is Claim Construction Really a Question of Law?

Phostech Lithium Inc v Valence Technology, Inc 2011 FCA 237 Pelletier JA: Noël, Mainville JJA, affirming 2011 FC 174, Gauthier J 

The trial decision of Gauthier J in Valence v Phostech turned primarily on the facts, and it is no surprise that the FCA has affirmed, in an appeal that “raises no novel questions of law” [1].

The invention in question was for a method for making lithium mixed metal cathodes for lithium ion batteries by using “carbothermal reduction” (CTR). The main issue at trial was whether the process used by Phostech, the defendant, used CTR. As a matter of science it was difficult to determine whether the conditions inside the closed industrial kiln used by Phostech would actually result in CTR, but the question, which Gauthier J decided against Phostech, was purely factual. Phostech chose, no doubt wisely, not to even raise this point on appeal.

Instead Phostech focused on a claim construction point. As the FCA noted, claim construction is a question of law, so the standard of review is correctness [26]. While this point is well settled, this characterization of claim construction has always struck me as a bit odd. The claim is construed as it would be understood by a person skilled in the art, which means that the trial judge must receive expert testimony as to the meaning of various terms and the background necessary to understand the technology, then use this factual information to put herself in the shoes of a skilled person reading the claims, before determining the meaning of the claims. This looks to me quite a lot like a question of mixed fact and law. In Phostech this FCA squared this circle by noting that “[w]hile the interpretation of the [term in issue] is a question of law, it must be construed in the light of the evidence as to its meaning to the person skilled in the art” [29]. The FCA then noted that the trial judge heard conflicting expert evidence, and preferred that of the plaintiffs’ [30], and after two paragraphs quoting from the trial judge’s summary of the evidence, concluded “the trial judge’s interpretation of the [term in issue], resting as it does on the evidence which she accepted as to the person skilled in the art’s understanding of the term, is unassailable” [33]. This looks quite a bit like a deferential review that would be applied to a question of mixed fact and law.

My thanks to Alan Macek and his very useful site IPPractice.ca for bringing this case to my attention before it was released on the FCA website.