If I had to, I would estimate that more than 50 percent of all patent litigation in Canada involves chemical subject matter. That shouldn’t come as a shock; chemistry, after all, is the central science! In view of this, I wouldn’t be surprised if many readers of the Canadian Chemical News have acted as expert witnesses during a patent suit.

In my last column, I discussed how terms in the claims of a patent need to be construed by a court during patent litigation. Claim construction, as it is called, is often critical to the outcome of a patent suit. The meaning of the terms in the claims of a patent influence much of a judge’s reasoning in finding whether there has been infringement, or whether a patent is held invalid. Previously, I used the word “thin” — in the context of a thin film of polyethylene on a packaging material — as a term that would likely have to be construed by a court. For example, if a judge found that the term “thin” meant between one to two millimetres, then a finding of infringement could only be found if the impugned product had a film in that range.

How does a judge arrive at a construction of a claim term? In Canada, the enquiry involves what a person skilled in the art would believe the claim term to mean in the context of the disclosure of the patent. For example, if the inventor specifically defined the term “thin” in the patent to mean one to two millimetres, then a judge would likely construe the term to have this particular thickness. Unfortunately, construction of a claim term is usually not that straightforward and therefore expert witnesses provide opinions to help a judge construe the contentious terms of a patent. 

As patent lawyers, we try to obtain the broadest protection we can for an inventor and therefore may draft a patent to functionally define a claim term such as “thin.” In the context of such an invention, a thin film of polyethylene may be present on the packaging material to prevent moisture from passing through the material. Accordingly, the term may be defined as the thickness of the polyethylene film required to prevent 99 percent of the moisture within the package from escaping over a three-month period. Experts from each side in the patent suit would then provide opinions as to the thickness required to achieve this result. Of course, the opinions would likely differ and a judge would have to provide reasons as to which opinion is preferable.

In a recent patent trial in Canada, the judge had to construe the term “inert” in the context of a pharmaceutical sub-coating. The patent at issue was directed to stable enteric pharmaceutical formulations of omeprazole, a proton pump inhibitor drug that decreases the amount of acid produced in the stomach. However, “inert” was not specifically defined in the patent. An expert for the alleged infringer argued that the term should be given its plain and ordinary meaning — that is, the sub-coating must not react with any other components in the formulation. An expert for the patent owner took the opposing view: an inert sub-coating simply meant that the coating would not interfere with the overall function of the enteric coating or the stability of omeprazole in the core of formulation. This view was supported by the patent, which identified certain sub-coatings that could potentially react with the other components of the formulation. Accordingly, the judge construed the term “inert” such that it would not preclude coatings that had a trivial amount of reactivity with the other components. Potential infringement of this claim limitation directly flows from the construction of the term. Clearly, expert witnesses play an important role during this exercise. 

Expert witnesses don’t just help construe claim terms but also provide scientific opinions concerning many issues during patent litigation, for example, whether an invention is obvious. From providing the initial opinion to being cross-examined in court, experts play an important role during a patent trial. So for all you chemical experts out there, don’t be surprised if someday, while working in your lab, you receive a call from a patent lawyer asking if you are willing to decipher a claim term. 

Mike Fenwick is a patent lawyer with Bereskin and Parr LLP in Toronto and holds a master’s degree in organic chemistry.