Convatec v Smith & Nephew: why the Court of Appeal was wrong

There's definitely something wrong ...

The IPKat has reported already twice on the interesting Court of Appeal, England and Wales, decision in Smith & Nephew Plc v ConvaTec Technologies Inc, relating to ConvaTec's patent EP (UK) 1,343,510 relating to silverised wound dressings (see Jeremy here, and this Kat here).  The Court of Appeal, reversing the first instance decision of Mr Justice Birss, held that a patent process claim that specified an "agent being present in a concentration between 1% and 25%" was infringed by Smith & Nephews's modified process in which the agent was present in a concentration of 0.77%.

This Kat was troubled by the decision, as he thought that the first instance decision was basically correct.

The Court of Appeal decision delivered by Lord Justice Kitchin considered what the description of the patent said about the concentration of the agent at [0028]:

The quantity of agent used will depend upon the amount of polymer-containing material being prepared and the total volume of solution. Preferably, the agent is present in a concentration between .01 and 50% of the total volume of treatment. In some embodiments, the concentration of agent is between .01-25%, .01-10%, .01-5%, .1-5%, .1-25%, .1-10%, 1-25%, 1-10%, 1-5%, 5-25%, 10-25%, or 25-50% of the total volume of treatment.

This paragraph, and the fact that the 1-25% range was introduced into claim 1 of the patent in the previous litigation proceedings between the parties, was key to Kitchin LJ's decision, as can be seen from the following three paragraphs from the judgment.

Second, it is apparent from the body of the specification that the patentee had well in mind the possibility of expressing numerical values with a very high degree of precision. Thus, in paragraph [0023], the patentee has identified a series of different silver concentration ranges using limits expressed, on some occasions, to an accuracy of zero decimal places but, on other occasions, to an accuracy of one decimal place. Similarly, in describing the permissible ranges of binding agent concentration in paragraph [0028], the patentee has used limits expressed with degrees of precision which range from zero decimal places to two decimal places. I believe this to be a powerful factor in favour of the interpretation of the claim for which ConvaTec contends. Against this background, I think the skilled person would understand that the patentee has chosen to express the numerical limits of the range in the claim to only a limited degree of accuracy.

Third, the reader is taught by paragraph [0028] and from the example at the end of the specification that the invention can (and preferably should) be performed with a binding agent concentration between 0.01 and 50%. This is a very wide range and it extends significantly beyond the limits of the claim. Once again this is a factor which undermines Smith & Nephew's favoured interpretation of the claim. It teaches the skilled person that there is no technical reason to read the claim as requiring the use of a binding agent concentration which falls between the exact numerical values of 1% and 25%.

... or thereabouts?

Fourth, I recognise that the concentration limits which appear in the claim have in a sense been chosen by the patentee as opposed to calculated by him or determined by experiment. Further they have been introduced into the claim by amendment. These are both matters upon which Mr Mellor has placed particular reliance but I do not believe they take him very far. However the patentee may have derived the numerical limits, the skilled reader seeking to put the invention into practice or satisfy himself that his process falls outside the scope of the claim must calculate his binding agent concentration or measure it. Either way he must do so with a particular degree of precision and the question is still whether the reader would understand the patentee intended the 1% and 25% limits of the claim to be understood as exact values or in a less precise way.

In the earlier consideration of this decision, I wrote:

This Kat wonders what has happened to the doctrine that "what is not claimed is disclaimed" - there is surely an argument that if it is taught that the invention can be performed with a binding agent concentration between 0.01 and 50%, but what is claimed is narrower, then this narrower range should be given a strict interpretation.  Yet Kitchin LJ took the opposite view - "Once again this is a factor which undermines Smith & Nephew's favoured interpretation of the claim."

But there is a further fact that seems to fatally undermine the reasoning in the three quoted paragraphs above, and that is that paragraph [0028] should not be in the amended patent at all.

Why not?

Well, practitioners before the European Patent Office will be well aware that, when a claim is narrowed during prosecution or post-grant in opposition proceedings, it is invariably required that the description be amended accordingly, and statements that go outside the scope of the amended claims should be excised.  Section 75(5) of the Patents Act 1977 states:

In considering whether or not to allow an amendment proposed under this section, the court or the comptroller shall have regard to any relevant principles applicable under the European Patent Convention.

Not Court of Appeal policy

One of the "relevant principles" is that the description must be adapted.  But that did not happen in the present case: claim 1 was allowed to be amended without any adaptation of the description.  It is not clear why this was permitted.  The UKIPO wrote a letter to ConveTec on 25 October 2011 (which can be seen at IPSUM here) confirming that the amendment was considered allowable, but also stating "However, consequential amendments should be made to the description with the insertion of a statement of invention that is consistent with the wording of the amended claim 1".  This did not happen.

The Court of Appeal has thus relied heavily on statements, such as "that the invention can (and preferably should) be performed with a binding agent concentration between 0.01 and 50%" when -- had correct procedure been followed -- those statements should simply not have been there.

Even if para [0028] was not amended, as it should have been, this Kat finds it most odd that the Court of Appeal should take the view that, when the claim has been narrowed in previous litigation to cure an invalidity problem, statements in the description that support the previous, invalid scope should be relied on to broaden the scope of the amended claim.