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Court of Appeal clarifies approach to insufficiency

Posted on 28 October 2019

The recent Court of Appeal decision in Anan Kasei v Neo Chemicals has considered the approach to questions of insufficiency and how to delineate the 'boundary' of protection.  Whilst the decision does not set out new principles, it does contain useful guidance.  In particular, as Lewison LJ put it in his supporting judgment (the main judgment is given by Floyd LJ), a 'fuzzy boundary' to a claim is not the same as it being impossible to ascertain the limits of protection: "the boundary may be fuzzy, but it is still a boundary".  If, however, the Court is unable to ascertain the boundary, using all available interpretive tools, the conclusion will be that the specification does not disclose the invention clearly and completely enough for it to be performed by a person skilled in the art, and hence it is insufficient.


The Patent (owned by Anan Kasei, with Rhodia as exclusive licensee) relates to ceric oxide (or ceria) and concerns a catalyst for purifying vehicle exhaust gases. The Patent has five product claims which relate to specific characteristics of a ceric oxide with a high surface area.  Claim 1 was in the following terms:

"A ceric oxide consisting essentially of a ceric oxide, and wherein said ceric oxide has a specific surface area of not smaller than 30.0 m2 /g when subjected to calcination at 900ºC for 5 hours".

Claim 1 was therefore limited through the wording "consisting essentially" of a particular oxide.  Neo argued that this made the Patent invalid as it gave rise to uncertainty.  Further, Claim 1 was limited by the reference to a desirable physical characteristic for such an oxide, namely a high specific surface area, and that it remains the same after being subjected to a high temperature heating test.  Neo argued that this meant the claim insufficiently described the invention.

At trial, the Patents Court Judge found the Patent valid, rejecting Neo's arguments of insufficiency.  Neo appealed to the Court of Appeal.  There were also certain procedural arguments relating to the joining of other Neo group companies into the claim (not considered in this note). 

'Consisting essentially of'

The Court of Appeal noted the distinction in 'patent jargon' of a claim for a composition of matter which 'consists' of something and one which 'comprises' something. Whereas 'consisting' will normally be taken to impose a requirement that nothing else is present, 'comprising' sets out a minimum requirement, meaning other things can be present. 

The Court of Appeal identified the words used in the Patent, i.e., 'consisting essentially of', as a 'hybrid' of these two formulations.  However, whilst the words might be thought to give rise to some uncertainty, in fact the skilled person would have regard to EPO practice to interpret such claims as meaning that, apart from the mandatory ingredient (here, ceric oxide), no other ingredients are present which materially affect the essential characteristics of the product.

Neo however argued that the specification did not contain any direction or explanation as to the meaning of 'consisting essentially of ceric oxide', and that therefore the skilled person would be unable to implement the invention without undue burden or at all.  It argued, relying upon a materiality test, that the skilled person would need to compare the alleged infringing sample with a control which, whilst otherwise identical, did not have the added ingredient.  This would give rise to difficulty: the Court used a cake analogy to explain Neo's argument.  The effect of the argument was that, in order to determine whether an added ingredient had a material effect, it would be necessary to take the ingredient out of a cake after it was cooked. 

The Patents Court had characterised this as an argument that the claim had a 'fuzzy boundary', but this did not lead to a finding of insufficiency.  The Court of Appeal agreed, and rejected Neo's claim of insufficiency on this ground.  There was no argument about the criterion that would be applied and tested for once construction of the claim was resolved. Further, the test was not whether a purchaser of the product could determine whether it infringes, but whether the specification discloses the invention clearly and completely enough for it to be performed by a person skilled in the art. Finally, and most fundamentally, the evidence did not support Neo's argument that determining whether a product was inside or outside the claim would impose an undue burden on the skilled person.  

It is worth noting that the Court of Appeal said it was inaccurate to describe this type of insufficiency argument as one focused on 'ambiguity'.  That term referred to a situation where the words were capable of more than one meaning.  Instead, the proper description was it was an argument of 'uncertainty': in the leading Kirin Amgen case, for example, the relevant claim was not struck down for insufficiency as it was ambiguous, it was because it was conceptually uncertain.  

Breadth of Claim 1

Neo's second insufficiency attack concerned he breadth of Claim 1, relying upon arguments considered by the House of Lords in Biogen and Lundbeck.  Neo argued that the claim merely described an obviously desirable product, and could have been written as a 'wish list', requiring no invention.  Having reviewed those decisions, the Court identified the claim as to a class of products identified by their composition, their physical characteristics and their performance in a calcining test.  To establish that the claim was insufficient due to its breadth, Neo had to positively establish, through its evidence, that there were structures which were covered by the claim which could not be made with the benefit of the teaching in the Patent.  Its evidence failed to do this.

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