When does Clarity become an Issue in the Opposition Procedure?

Many of the skilled readers will know that clarity of the claims is not a ground of opposition under the EPC. Clarity of all the claims is supposed to examined in the examination procedure and treated as something like res judicata  in the subsequent opposition procedure. G 09/91 states, however, that amendments of the claims are to be fully examined as to their compatibility with the requirements of the EPC (including clarity).

In principle, Art. 84 EPC applies to all of the claims, the independent ones and the dependent ones. As a consequence, most of the boards have interpreted  G09/91 in such a way that mere combinations of formerly dependent claims do not introduce subject-matter which has not yet been examined for clarity and therefore do not open the power of an Opposition Division or a Board of Appeal to examine the clarity of amendments of this kind. However, there is a recent tendency to deviate from this line (see e.g. here) or to circumvent Art. 84 EPC via Art. 83 EPC by arguing that the claim is so unclear that the specification does not enable the skilled person to carry it out.

Experience shows that the concentration of both examiners and attorneys rapidly decreases once they have successfully read and understood claim 1 and that the clarity of the claims tends to decrease with increasing number.

This may lead to problems when a dependent claim including its shortcomings is suddenly placed in the limelight by being incorporated into an amended claim 1. Both opposition divisions and opponents have to control their well-trained reflexes to scrutinize the clarity and are sometimes obliged to even support highly allergenic words like "substantially" in a claim 1.

The latter was the fate of the technical board of appeal in the decision T 373/12, which was faced with the nuisance that the formulation "substantially all of its surface area" had found its way from claim 3 as granted into an amended claim 1. It has therefore referred the following questions to the enlarged board of appeal:

1. Is the term "amendments" as used in decision G 9/91 of the Enlarged Board of Appeal (see point 3.2.1) to be understood as encompassing a literal insertion of

(a) elements of dependent claims as granted and/or

(b) complete dependent claims as granted into an independent claim, so that opposition divisions and boards of appeal are required by Article 101(3) EPC always to examine the clarity of independent claims thus amended during the proceedings?

2. If the Enlarged Board of Appeal answers Question 1 in the affirmative, is then an examination of the clarity of the independent claim in such cases limited to the inserted features or may it extend to features already contained in the unamended independent claim?

3. If the Enlarged Board answers Question 1 in the negative, is then an examination of the clarity of independent claims thus amended always excluded? 4. If the Enlarged Board comes to the conclusion that an examination of the clarity of independent claims thus amended is neither always required nor always excluded, what then are the conditions to be applied in deciding whether an examination of clarity comes into question in a given case?