About 70% of EPO oppositions involve the claims being amended. An opponent or an opposition division may wish to object that the claims are unclear, either due to the actual amendments made or perhaps due to a pre-existing lack of clarity. The catch is that lack of clarity is not itself a ground of opposition and there has been disagreement over the years over how far clarity can be examined when the claims have been amended.

This question has now been definitively addressed in decision G 3/14 which has just issued from the Enlarged Board of Appeal. This decision rewrites the law on clarity examination in EPO oppositions and will have a major influence on many cases pending at the EPO. A copy of the decision, which is not yet listed in the case law area of the EPO website, can be downloaded (PDF) from here.

The one sentence summary is that clarity examination in opposition must henceforth be of a much more limited scope than the more recent case law would suggest.


Alleged lack of clarity of the claims (Article 84 EPC) is excluded as a possible ground of opposition, but Article 101(3) says that the opposition division must examine whether the amended patent meets the requirements of the EPC in coming to its decision to maintain or revoke the patent. Whether this latter provision means that the opposition division or board of appeal must examine the amended claims for clarity is a recurring issue, and one which has given rise to two diverging lines of case law, which you can read about in detail in the decision itself, or in the referring decision T 373/12.

The Enlarged Board was asked to give an opinion on whether it was allowable to examine the clarity of amended claims in cases where elements of a dependent claim were added to an independent claim, and if so, to clarify how extensive that clarity examination ought to be.

Surprisingly perhaps, but in a move that practitioners, examiners and appeal boards must welcome for the increased certainty that it brings (even if the outcome does limit the ability of examiners and opponents to challenge the clarity of claims), the Enlarged Board has used this referral as an opportunity to go far beyond the narrow question of combining dependent claim elements (or complete dependent claims) and has reviewed the entire subject of clarity in opposition proceedings de novo in a major judgment which rewrites the law on clarity examination post-grant.

The existing case law

The “conventional” jurisprudence (to use the Enlarged Board’s terminology) is exemplified by T 301/87, which is the sort of landmark decision that most young children who yearn to be patent attorneys learnt while sitting on their grandfather’s knee. According to this approach when claims are amended in opposition proceedings, objections of lack of clarity cannot be raised if the objections “do not arise out of” the amendments made.

The “diverging” cases, again using the Board’s terminology, are represented by T 1459/05 in its more moderate form and by T 459/09 in its more extreme form. T 1459/05 said that the clarity of a combination of dependent claim 4 with independent claim 1 was to be examined as an exception, due to the fact that the added feature was both unclear and yet was the only possible distinguishing feature over the prior art. In T459/09 the Board held that where claims were amended with a technically meaningful feature, this justified an “unrestricted exercise” of the examination power under Article 101(3).

As regards what it means for a lack of clarity to “arise out of” an amendment, this was initially interpreted (in T 301/87) as follows: a lack of clarity “arises” from an amendment when it did not exist before, so that the effect of the amendment is to give rise to a lack of clarity for the first time. However in T 472/88, the Board went further in a statement that has been followed in many decisions over the years. Here the Board looked to the Oxford Dictionary definition of “arise”: “originate, be born, result from, come into notice, present itself”. Later decisions both approved this broad definition and extended it to include “concealed” lack of clarity which then was “made visible” after the amendment. Although the referral did not ask the Enlarged Board to look at this aspect of clarity, the Enlarged Board did so.

Three major points from the decision

1. The answer to the referred questions

The Enlarged Board was given a series of questions, the first being:

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?

Questions 2, 3 and 4 explored the implications of a yes or no answer to question 1. The Board noted that the issue was not the interpretation of G 9/91 (as the referring Board had put the question) but rather the proper interpretation of Article 101(3), and it considered that in answering question 1(a), all of the referred questions were also dealt with:

The questions referred to the Enlarged Board of Appeal are answered as follows:

In considering whether, for the purposes of Article 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 Article 84 EPC only when, and then only to the extent that the amendment introduces non-compliance with Article 84 EPC.

2. Which approach is correct: T 301/87 (conventional) or T 1459/05 & T 459/09 (diverging)?

The Board explicitly says [Reasons, 87]:

The Enlarged Board thus approves the conventional line of jurisprudence as exemplified by T 301/87 (section E(a), points 18 to 26, above), and disapproves [...] the line of “diverging” jurisprudence (as exemplified in the cases set out in section E(c), points 30 to 43, above).

In other words, the Enlarged Board has gone back to basics and a much more limited scope for examination of clarity than the more recent case law had suggested was appropriate.

3. When does a lack of clarity “arise out of” an amendment?

Eagle eyed readers will see that we edited out some text in the preceding quotation. The missing part deserves its own spotlight:

The Enlarged Board thus approves the conventional line of jurisprudence [...] and disapproves the line of jurisprudence as exemplified by T 472/88 (explained in section E(b), points 27 to 29, above) [...]

T 472/88 was the case where “arises out of” was given a broad construction based on the OED definition, i.e. “originate, be born, result from, come into notice, present itself” . The Enlarged Board enlarged (sorry) on this particular point at [Reasons, 29], saying:

In the Enlarged Board’s view, development of the jurisprudence of the Boards of Appeal in this way [interpreting "arise" to include each of the synonyms given in the dictionary definition] is not legitimate. It is of course appropriate to use a dictionary when interpreting a statute to help elucidate its meaning, but statements in a decision of a court using ordinary words do not require further interpretation in this way: they are to be understood in their context. Given the facts of those cases (see points 18 and 20, above) the Enlarged Board does not consider that the Boards there intended these words to have the expanded meaning given to them in T 472/88 and the later cases which followed this approach. In any event, it is unclear to the Enlarged Board what the test developed on the basis of this construction actually amounts to or when precisely an amendment can be said to bring into notice, highlight or focus attention on a previously existing ambiguity (see further, point 80(k), below). This line of cases has not generally been regarded as belonging to a diverging line of cases (although it was identified as such in T 1577/10).