The extent to which the opposition division or a board of appeal may examine clarity for the purpose of Art. 101(3) EPC was the subject of questions put to the Enlarged Board of Appeal in referral G 3/14 (OJ 2015, A102). In the case underlying the referral (T 373/12 date: 2014-04-02, OJ 2014, A115) claim 1 of auxiliary request 1, submitted during opposition proceedings, consisted of a combination of the features of claim 1 as granted and of dependent claim 3 as granted.
As a preliminary point, the Enlarged Board identified the following main types of case: amendments which encompass a literal insertion of elements of dependent claims as granted into an independent claim (type A); these include amendments in which a dependent claim contains within it alternative embodiments, one of which is then combined with its independent claim (Type A(i)), and amendments in which a feature is introduced into an independent claim from a dependent claim, being a feature which was previously connected with other features of that dependent claim from which it is now disconnected (Type A(ii)); furthermore, amendments which encompass a literal insertion of complete dependent claims as granted into an independent claim (Type B, this being the case with which the referring board was confronted).
The Enlarged Board first considered its previous jurisprudence, i.e. G 1/91 (OJ 1992, 253), G 9/91 (OJ 1993, 408) and G 10/91 (OJ 1993, 420). Citing the statement in point 19 of the Reasons in G 9/91 and G 10/91 that "[...] in case of amendments of the claims or other parts of a patent in the course of opposition or appeal proceedings, such amendments are to be fully examined as to their compatibility with the requirements of the EPC", it noted that if the Enlarged Board had at the time considered that the opposition division and the boards of appeal were given wide powers to examine amended claims, it would have said so. Therefore, the term "amendments" had to be understood in the sense that the subject-matter to be examined must have some direct nexus with the amendment.
The Enlarged Board identified three main lines in the jurisprudence of the technical boards: the "conventional" approach, based on the test whether the amendment introduces any contravention of Art. 84 EPC, and the principle that Art. 101(3) EPC does not allow objections to be based upon Art. 84 EPC if they do not arise out of the amendments made (see T 301/87 and T 227/88, applied in many further cases, see e.g. T 381/02, T 1855/07, T 367/96 of 3 December 1997 date: 1997-12-03 and T 326/02). Secondly, there was a wider interpretation, according to which a lack of clarity could be examined if the amendment "highlights and focuses attention" on a previously existing ambiguity (T 472/88; see also T 681/00 and T 1484/07). The third line of jurisprudence was considered "diverging". According to T 1459/05 (see also T 1440/08 and T 656/07), clarity may be examined on a case-by-case basis as a matter of discretion when the added feature is the only feature that distinguishes the subject-matter of the claim from the prior art. T 459/09 was the most far-reaching of these diverging cases, stating that amended claims may generally be examined for clarity on a case-by-case basis irrespective of the kind of amendment.
On the interpretation of Art. 101(3) EPC the Enlarged Board pointed out that the requirements of Art. 84 EPC are part of the "requirements of the Convention" for the purposes of Art. 101(3) EPC. There was, however, no indication that the object and purpose of Art. 101(3) EPC was to open up the patent to a complete re-examination, whether for clarity or the other requirements of the EPC. It was rather the amendment itself which was relevant, and its effect for the ground for opposition in question. Self-evidently, the amendment must not itself give rise to new objections.
As apparent from the travaux préparatoires to the EPC 1973, the legislator had deliberately chosen not to make Art. 84 EPC a ground for opposition. It would be unsatisfactory if an opponent could cause delays whenever an amendment was made, by raising all kinds of Art. 84 EPC objections. Moreover, a lack of clarity could still be relevant in opposition proceedings in that it could influence the decision on issues under Art. 100 EPC (sufficiency, novelty, inventive step), or impact on the grounds of invalidity alleged in national proceedings relating to a European patent. Furthermore, when the EPC 2000 was drafted, no suggestion was made for a change to reverse the effect of the then established case law, i.e. the conventional approach based on T 301/87. If the deletion of an independent claim with its dependent claims permitted examination of the remaining claims for lack of clarity, Art. 84 EPC would effectively become a ground for opposition in a large number of cases, which would be contrary to the legislator's intention. To conclude otherwise for a combination of claims which actually consists of striking out the original independent claim and then writing out the previously dependent claim in full, would be arbitrary and unjustified.
In conclusion, the Enlarged Board approved the conventional line of jurisprudence as exemplified by T 301/87, and answered the referred questions as follows:
"In considering whether, for the purposes of Art. 101(3) EPC, a patent as amended meets the requirements of the EPC, the claims of the patent may be examined for compliance with the requirements of Art. 84 EPC only when, and then only to the extent that, the amendment introduces non-compliance with Art. 84 EPC."
In T 616/12 (issued before decision G 3/14 above) the board held the appellant's objections to lack of clarity in amended claim 1 to be inadmissible. An objection to the clarity of granted claims was not foreseen in the opposition procedure, as lack of clarity was not a ground for opposition. Since claim 1 was a combination of granted claims 1 and 15, a clarity objection to it was tantamount to raising an objection of lack of clarity to the claims as granted. Furthermore, it was not apparent how a lack of clarity resulted from an amendment caused by combining the granted claims. See also e.g. T 1577/10.
Considering the different types of amendment distinguished in G 3/14, the board in T 1112/12 observed that a common theme underlying the Enlarged Board's ruling appeared to be that modifying a claim by merely deleting or excluding embodiments from the claimed subject-matter does not result in an amendment which is open to an objection under Art. 84 EPC (see also T 1977/13 and T 260/13). For further cases where the lack of clarity was already present in the claims as granted and the clarity objection therefore rejected, see T 266/15 and T 488/13.
In T 248/13 certain ambiguous terms were already contained in claim 15 as granted. However these terms defined the flavour of the final product, whereas the terms of claim 1 of auxiliary request 1 referred to an ingredient to be added. The board considered that by taking these terms out of the context in claim 15 as granted and placing them in the context of claim 1 of auxiliary request 1, a new ambiguity was introduced that was not present before. Therefore this amendment was objectionable under Art. 84 EPC.