The High Court held that any future patent infringement in a quia timet action would be de minimis, and that to grant an injunction would be both disproportionate and a barrier to legitimate trade.


A patentee does not need to establish that the defendant has already committed a wrongful act in order to commence infringement proceedings. Proceedings may be commenced if the defendant threatens to do an act which will infringe the patent (quia timet claims).

Remedies for patent infringement, in particular injunctions, must be effective, proportionate and dissuasive, and must be applied so as to avoid the creation of barriers to legitimate trade and to provide for safeguards against their abuse (Article 3(2), Intellectual Property Enforcement Directive (2004/48/EC)) (Enforcement Directive).

The meaning and scope of a numerical range in a patent claim is ascertained in light of the common general knowledge and in the context of the specification as a whole. In the absence of a clear indication in the patent, the skilled person will understand that the patentee had chosen to express numerals in the claim to a particular but limited degree of precision and so intended the claim to include all values which fell within the claimed range when stated with the same degree of precision (Smith & Nephew plc v Convatec Technologies Inc,


N owned a European patent for a seven-day transdermal patch for the treatment of pain. S obtained a UK marketing authorisation for a competing transdermal patch. R intended to market a transdermal patch, but had not yet received marketing authorisation.

N sued for patent infringement and applied for an interim injunction against S. S gave temporary undertakings.

N also sought an interim injunction against R. R counterclaimed for a declaration of non-infringement.


The court held that neither S’s nor R’s products would fall within the patent claim, so there was no threat by S or R to infringe N’s patent.

The patent claim was expressed in terms of percentage weights of various components. In a scientific context the precision with which numbers are expressed is dictated by the number of significant figures or decimal places. In order to compare one number which is expressed to a particular degree of precision with another which is expressed to a different and greater degree of precision, it might be necessary to round the second number to the same degree of precision as the first, in accordance with the standard convention.

Here, the numerical limits in the claim were construed as being expressed to the nearest whole number. The term “about” in the claim did not make the claim invalid, but rather connoted a small degree of permitted imprecision over that implied by the usual rounding convention.

If there was a clear threat to do acts which would fall within the claim sufficiently often that they could not be discounted as de minimis, then that was sufficient to justify the bringing of proceedings on a quia timet basis. Whether it was sufficient to justify the grant of an injunction was a separate question. N bore the burden of proving that the acts which S proposed to do in the period before expiry of the patent would result in infringement on a scale which was more than de minimis.

The manufacturing processes used to produce patches were inherently variable. So, even if the specification for S’s product was intended to ensure that the percentage of a particular content of the patch was outside the claimed range, it was inevitable that some patches would have more and some less. Analytical techniques were not precise. Therefore, even when dealing with past infringements, there could not be a precise answer to the question of the percentage which fell within the claimed range.

Most of the patches had not yet been manufactured. Since the testing was destructive, it would be necessary to test only a representative sample rather than all the patches. It was not possible from the tests carried out to date to determine how representative the tested samples were of the whole population.

The standard of proof for civil claims was the balance of probabilities. N should not be subjected to a more stringent burden of proof in relation to future as opposed to past events. R should likewise not be subject to a higher standard of proof in its claim for a declaration of non-infringement.

N had to prove, on the balance of probabilities, what proportion of patches would fall within the claim, and whether that proportion was more than de minimis. The answer to the first issue would inevitably be affected by the uncertainties caused by the lack of precision in the analytical data and the relatively small number of samples tested so far. A statistical test which took these matters into account had to be applied.

N chose to accept the analytical data relied on by S based on the small number of samples tested so far instead of waiting for a larger quantity of data. N could not take advantage of the uncertainties relating to the statistical test and must accept that these uncertainties made it more difficult to establish on the balance of probabilities what proportion of patches would fall within the claim.

Applying the Enforcement Directive, an injunction would be disproportionate because the harm to the patentee from infringement on such a small scale would be indistinguishable from the harm caused by wholly non-infringing acts. It would also be a barrier to legitimate trade because the practical effect of an injunction would be to require S and R to operate even further outside the boundaries of the claim, effectively extending the scope of N’s monopoly.

As regards numerical ranges in patent claims, the court’s reasoning here followed that applied in Convatec. However, other issues such as how to apply the de minimis principle, and how to apply it in relation to a quia timet claim, have not previously been judicially considered in patent actions.

The decision also illustrates the difficult practical problems for a patent owner in bringing a quia timet action where proof of the threat to infringe depends on the complex analysis of a small number of samples, and where S and R were sophisticated manufacturers with knowledge of the patent and products intended to avoid its claims. The decision also provides guidance in using complex statistical expert evidence to establish the probability of future infringements, particularly in the context of variable manufacturing processes.

Case: NAPP Pharmaceutical Holdings Ltd v Dr Reddy’s Laboratories (UK) Ltd and another [2016] EWHC 1517 (Pat).

First published in the August 2016 issue of PLC Magazine and reproduced with the kind permission of the publishers.