Smith & Nephew Plc (Respondent/Appellant) v ConvaTec Technologies Inc. T J Smith & Nephew Ltd and Another (Third Parties)
| Jurisdiction | England & Wales |
| Judge | Lord Justice Kitchin,Lord Justice Briggs,Lord Justice Christopher Clarke |
| Judgment Date | 24 June 2015 |
| Neutral Citation | [2015] EWCA Civ 607 |
| Court | Court of Appeal (Civil Division) |
| Docket Number | Case No: A3/2014/0284 |
| Date | 24 June 2015 |
and
[2015] EWCA Civ 607
Lord Justice Kitchin
Lord Justice Briggs
and
Lord Justice Christopher Clarke
Case No: A3/2014/0284
IN THE COURT OF APPEAL (CIVIL DIVISION)
ON APPEAL FROM THE HIGH COURT OF JUSTICE
CHANCERY DIVISION (PATENTS COURT)
The Hon Mr Justice Birss
Royal Courts of Justice
Strand, London, WC2A 2LL
Piers Acland QC and Thomas Alkin (instructed by Bird & Bird LLP) appeared on behalf of the Appellant
James Mellor QC and Charlotte May QC (instructed by Bristows LLP) appeared on behalf of the Respondent/Appellant and Third Parties
Hearing dates: 16/17 April 2015
Introduction
This appeal concerns the scope of a patent claim which contains a numerical range. It forms the next stage of a long running dispute between the claimant and third parties (together, "Smith & Nephew"), on the one hand, and the defendant ("ConvaTec"), on the other.
ConvaTec is the owner of European Patent (UK) No 1,343,510 ("the Patent") which is concerned with a process for the silverisation of gel-forming fibres used in wound dressings. Silver is a known antimicrobial agent but a problem with silver-containing materials is that they are often sensitive to light and discolour on exposure to it for any length of time. The patented invention is said to solve this problem by providing a method of making light stabilised silverised antimicrobial materials. In broad terms, the method comprises three steps. The first involves preparing a solution comprising an organic solvent and a source of silver. The second involves subjecting gel-forming fibres containing particular polymers to the silver solution. The third (which may be carried out during or after the second) involves subjecting the gel-forming fibres to an agent, such as a chloride salt, which facilitates the binding of the silver to the polymers. Importantly, the relevant patent claim says that the agent must be present in a concentration of "between 1% and 25% of the total volume of treatment". It is the meaning of this phrase which has given rise to these proceedings.
In earlier proceedings between the parties, Smith & Nephew sought an order for revocation of the Patent so as to clear the path for a new range of silverised gel-forming wound dressings which they wished to sell under the brand name Durafiber Ag. Those proceedings came on for trial before Birss J. He allowed an amendment of the Patent and rejected the claim for revocation ( [2012] EWHC 1602 (Pat), [2013] RPC 8), and his decision was subsequently upheld by this court on appeal ( [2012] EWCA Civ 1638, [2013] RPC 9). This outcome was, as Birss J observed, a blow to Smith & Nephew because they had by this time developed a process for making Durafiber Ag and had obtained a CE mark regulatory approval to sell products made in accordance with that process in the European Union, and they were now at risk that it might be found to infringe the Patent.
Smith & Nephew responded to this set-back by developing a new process ("the Modified Process") which they thought would not infringe the Patent. This process comprises the steps of the patented method save that the concentration of binding agent is no more than 0.77%, and in January 2013 they began these proceedings for a declaration of non-infringement.
ConvaTec counterclaimed that the Modified Process did infringe the Patent, and that so too did an earlier process Smith & Nephew had used in various experiments carried out by way of process development. This further allegation, arising as it did from the use of the earlier process ("the Original Process"), was said to be a serious matter because the data generated from carrying that process out were relied upon by Smith & Nephew in support of their application for marketing approval. ConvaTec originally complained about over 80 different experiments but, at the end of the day, only four remained in issue and the concentration of binding agent used in them ranged from 0.93% to 0.97%, depending on how it was calculated.
The trial came on before Birss J in November 2013 and in his judgment given on 12 December 2013 ( [2013] EWHC 3955 (Pat)) he held that the Modified Process did not infringe the Patent but that the Original Process did. In order to understand the issues arising on the appeal, I must explain in outline how he arrived at these conclusions.
The judge began by construing the patent claim. The critical phrase to which I have referred gave rise to two issues, namely the numerical boundaries of the claim and the meaning of the words "total volume of treatment".
On the numerical boundaries issue, ConvaTec contended that the expression "between 1% and 25%" did not define precise values but would be seen in terms of whole numbers and so, applying the basic rounding convention, the claim encompassed all concentrations greater than or equal to 0.5% and less than 25.5%. By contrast, Smith & Nephew's primary contention was that the expression meant what it said and that it defined a range of concentrations, with a lower limit of precisely 1% and an upper limit of precisely 25%. But Smith & Nephew also had a fall back position, namely that the 1% and 25% limits would be read in terms of significant figures, and that 0.95% and above would be understood to round up to 1%, and that 25.49% and below would be understood to round down to 25%, and so the claim encompassed all concentrations greater than or equal to 0.95% and less than 25.5%.
The judge rejected ConvaTec's contention that the lower limit of the claim was 0.5%, and he also rejected Smith & Nephew's primary contention that its lower limit was precisely 1%. He concluded that the skilled person would look at the limits in terms of significant figures and that the claim therefore included concentrations greater than or equal to 0.95% and less than 25.5%. This conclusion has been heavily criticised by both ConvaTec and Smith & Nephew on this appeal, as I shall explain.
The dispute about the meaning of the words "total volume of treatment" arose because, as was common ground, the process of the invention may be carried out in two different ways. The first, referred to as "the during process", involves exposing the material to the silver solution and the binding agent sequentially in the same vessel. The total volume of treatment is then the volume of silver solution and the volume of binding agent solution added together. The second, referred to as "the after process", involves exposing the material to the silver solution first, and then to the binding agent solution. The material may, for example, be removed from one vessel containing the silver solution and transferred to another vessel containing the binding agent solution, or the silver solution may be drained away before the binding agent solution is added. But in either case, the nature of the material is such that a good deal of the silver solution is likely to be carried over from the one stage to the other. The question for the judge was whether this residual silver solution, referred to as "carryover", forms part of the "total volume of treatment". He held that it does, despite the fact that determination of the volume of carryover may prove difficult, as it did in this case. Neither side has appealed against this conclusion.
The judge then came to the issue of infringement. It followed from his findings on construction that the Modified Process, using as it does a concentration of binding agent of no more than 0.77%, does not infringe. The volume of carryover could not make a difference to this conclusion and the judge so held.
The Original Process, as used in the four experiments which remained in issue, was not so straightforward. Without taking into account carryover, the concentration of binding agent certainly fell within the Patent claim for it was in all cases in excess of 1%. But once carryover was taken into account it fell much closer to the lower boundary line. In Smith & Nephew's process description, the concentration was said to vary from 0.96–0.97%. These figures were derived by considering the theoretical absorbency of lyocell, one of the kinds of fibre found in the material, and so, on the judge's construction, each of the experiments infringed. But at trial Smith & Nephew contended that a more accurate assessment of carryover could be derived from measuring the volume of liquid contained in the fibre material at the end of the process. This method, referred to as the empirical method, yielded a higher value for carryover than the theoretical method and hence a lower concentration of binding agent. Indeed for each of the four experiments in issue, the empirical method yielded a concentration of binding agent of 0.93–0.94%, that is to say below the lower boundary of the claim as the judge had construed it.
The judge heard a good deal of evidence on this issue but concluded that the figures based upon the empirical method were not dependable and that he could not be sure that they were sufficiently conservative for him to disregard any uncertainties inherent in them. He held that the only reliable figures before him were those contained in Smith & Nephew's product and process description and so the four experiments did infringe the Patent. Upon this appeal Smith & Nephew contend that this conclusion was contrary to the evidence.
These appeals therefore gave rise to two principal issues:
i) the correct...
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