T 0608/07 - Ambiguities in the claim (sufficiency vs. clarity) - rank #97

Rank: 97
Number of citations: 55

This appeal against a decision of an opposition division in case deals with the question of whether and when difficulties in determining the scope of the claim, i.e., ambiguities, are to be regarded a clarity issue (not a ground of opposition) or as pointing towards insufficiency of disclosure (a ground of opposition, Art. 100(b)).

An earlier decision, T 256/87, held that - in order to be able to carry out an invention - the skilled person must know whether a certain embodiment "falls within the forbidden area of the claim" or not. Otherwise, the invention could not be carried out in a targeted manner.

Since then, T 256/87 has been used by opponents to interpret a clarity issues as a lack of sufficieny. Also the respondent/opponent in T 608/07 made a similar attack under Art. 100(b) against the claims at issue.

The claims in T 608/07 defined a polymerisation process, in which two "incompatible catalysts" were used. The description provided a definition of the term "incompatible catalyst", which was, i.a., based on a comparison of the average molecular weights of the polymers that were produced by each of the catalysts. The numerical value of the average molecular weight of a polymer, however, depends on how the average molecular weight is calculated. Specifically, it plays a significant role whether the weight average molecular weight (Mw) is used, or whether the number average molecular weight (Mn) is used. The opponent showed that using the number average mean molecular weight, two tested catalysts were to be regarded as "compatible", whereas using weight average molecular weight, the same two catalysts were "incompatible". The respondent/opponent argued that this resulted in a situation where the skilled person could not carry out the invention.

Under the specific circumstances of the case, the Board found that the skilled person would readily understand the expression "molecular weight" to mean weight average molecular weight. The alledged difficulty in deciding whether one operates "within the forbidden area of the claim" therefore did not exist.

However, the Board added a general statement on the "forbidden-area" concept of T 256/87. The Board stated:

"2.5.2 The issue of insufficiency dealt with in T 256/87 and the present case is an insufficiency which arises through ambiguity. Although the board accepts that, depending upon the circumstances, such an ambiguity may very well lead to an insufficiency objection, it should be born in mind that this ambiguity also relates to the scope of the claims, ie Article 84 EPC. Since, however, Article 84 EPC is in itself not a ground of opposition, care has to be taken that an insufficiency objection arising out of an ambiguity is not merely a hidden objection under Article 84 EPC. It is the conviction of this board that for an insufficiency arising out of ambiguity it is not enough to show that an ambiguity exists, eg at the edges of the claims. It will normally be necessary to show that the ambiguity deprives the person skilled in the art of the promise of the invention. It goes without saying that this delicate balance between Article 83 and 84 EPC has to be assessed on the merits of each individual case."

In other words, not in every case where there is ambiguity in the claims, this can be translated into insufficiency of disclosure. Only where the ambiguous feature concerns the core of the invention, as opposed to the "edges of the claims", then an objection under Art. 83/100(b) may be justified.

Since then, the question of whether ambiguity in the claims is a matter of clarity or sufficiency of disclosure had frequently been debated in opposition proceedings.

A recent decision (T 2290/12, mentioned in the EPO's 2017 Case Law Report, Suppl. Publ. 3 of the OJ) has summarised the debate and concluded that the "forbidden area" concept of T 256/87 has only been followed in four decisions, whereas the approach of T 608/07 was applied in more than 20 cases. The Board in T 2290/12 stated that the "forbidden area" concept "appeared to have been dropped".

The "forbidden area" concept, however, is not dead. In T 1914/11 the Board found that difficulties in determining the "transient pH in the mouth" of a subject resulted in insufficiency of disclosure. The patent was revoked under Art. 100(b). More recently, in T 626/14, difficulties in measuring the thickness of a "fluffy absorbent core", which was a parameter used to define the invention, rendered claim 1 insufficiently disclosed.

Generally, however, ambiguities in patent claims are nowadays more likely to be regarded a matter of clarity than insufficient disclosure.

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Headnote:

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The full text of the decision can be found here.