There has been much discussion recently of the Court of Appeal decision Smith & Nephew v Convatec (see, for example, the IPKat blog posts here and here). The case relates to a method claim in Convatec’s patent EP1343510, in which a particular chemical agent is defined as being present in a concentration “between 1% and 25%”, and whether this claim is infringed by Smith & Nephew’s method which uses a concentration of 0.77%.
At first instance, Mr Justice Birss held that the “1%” at the lower end of the range would be understood to encompass concentrations as low as 0.95%, reasoning that because the “1%” of the claim was itself written to one significant figure it should include all values equal to 1% when rounded to one significant figure. Under this approach, the 0.77% of Smith & Nephew’s method lies outside the claimed range and so was not held to infringe.
The Court of Appeal reversed this decision, finding that “1%” actually includes concentrations as low as 0.5%, on the basis that all concentrations equal to 1% when rounded to the nearest whole number should be included. Therefore Smith & Nephew’s 0.77% does indeed fall within the scope of the claim. This decision has been met with surprise, not least because it seems to suggest that, in the world of patent claims, we may find ourselves in a situation where 0.77% is considered greater than 1%.
Before deciding upon matters of infringement and validity of a patent, the courts must construe the claims in order to determine their precise meaning. The key test employed by the UK courts was famously set out in Kirin-Amgen. The test requires the court to ask what the skilled person would understand the patentee to mean by the claim language they used. Also following Kirin-Amgen, the notional skilled person is supposed to assume that the claim wording was chosen by the patentee with “great accuracy and subtlety”.
In the present case, various arguments and corroborating expert evidence were presented by both sides, suggesting that the skilled person would understand the patentee to have meant very different things by the “1%” of the claim. These span from 1% precisely (according to Smith & Nephew) down to 0.5% (according to Convatec).
In Catnic Components Ltd v Hill & Smith Ltd  R.P.C. 183, some leeway was given in construing the claim wording “extending vertically” to include slight deviations from the vertical, in order to ensure fair protection for the patentee. But it is interesting to consider whether such leeway should be given when the patentee defines his invention in terms of numbers, rather than words. If the patentee does indeed formulate his claims with the required accuracy and subtlety then presumably he should be using whatever precise numerical values are necessary to bound the range at its upper and lower ends. Claiming “1%” with the intention of it meaning 0.5% appears to be neither accurate nor subtle.
The Protocol on the Interpretation of Article 69 EPC requires that, when considering Article 69 EPC (which itself requires that the protection conferred by a patent is defined by the claims as interpreted by the description) one should arrive at a position which combines fair protection for the patentee with a reasonable degree of legal certainty for third parties. The Court of Appeal decision seems to be stacked very much in favour of the patentee, whilst leaving third parties with a good deal of legal uncertainty as to what numerical expressions used in claims really mean.
Experimentalists measuring physical quantities, such as chemical concentrations, would routinely state the measured values to a certain degree of accuracy. Thus a measured concentration of 0.77% would typically imply that, given the uncertainty inherent in the way that particular value is measured, the actual concentration lies somewhere in the range 0.765% to 0.775%. One cannot help worrying slightly at the way in which similar considerations are being applied by the courts, not to an experimentally-determined measurement, but to a value which is simply written down to define a point on the number line and has no “uncertainty” associated with it at all.
In any case, even if the “1%” referred to at the lower end of the claimed range really does mean all numbers that round to 1% using the whole number approach, then why should the lower end of the claimed range be set to 0.5% instead of, say, 1.45%? Further, does the Court of Appeal decision imply that the patentee could, if they so wanted, amend their claimed range from the original “between 1% and 25%” to “between 0.6% and 25%”, safe in the knowledge that the scope of protection of his patent has actually been reduced by such an amendment (and that consequently there ought to be no risk of offending against Article 123(3) EPC)? It is very difficult to see the skilled person understanding the former of these ranges to be wider in scope than the latter.
One way out of this troublesome state of affairs is to take a step back and read the claim as meaning, quite simply, what it says. This way the patentee is given a fair shot at protection because he is able to specify numerically the boundaries of his range exactly as he wishes, using the “great skill and accuracy” available to him. At the same time, third parties need not worry about boundaries shifting depending on which particular rounding convention is used at such a time as the claims come to be construed by the courts. This can only result in an improvement to their legal certainty.
It remains to be seen if any appeal to the UK Supreme Court may return a little common sense to what is, fundamentally, a debate over the meaning of “1”. In the meantime, those considering drafting or interpreting patent claims defining numerical ranges ought to be proceeding with great care.
This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.