In T 607/10 the board considered that, in deciding whether a new argument has the effect of amending a party's case within the meaning of Art. 13(1) RPBA 2007, it must be established on a case-by-case basis whether the new argument is a departure from, or just a development of, the original arguments filed with the grounds of appeal or the reply thereto. In the case at hand, the new argument could not be seen as merely a further development or elaboration of the opponent's previous position. The new analysis was based on a different choice of the closest prior art. This new argument had therefore to be seen as constituting an amendment to the opponent's case within the meaning of Art. 13(1) RPBA 2007, which might be admitted and considered only at the discretion of the board. In the case at hand, the board, in the exercise of its discretion, decided to admit the new arguments put forward by the opponent. See also T 704/06 (ex parte), T 1941/10, T 216/10 and T 174/12, where the late-filed arguments were also admitted into the proceedings.

During the oral proceedings in the similar case T 55/11, when discussing inventive step of granted claims 1 and 20 starting from document D1 and taking into account document D13, the appellant (opponent) argued for the first time that the subject-matter of said claims also lacked an inventive step starting from document D13 and taking into account document D1. The board followed the case law reported above and admitted the new arguments. In its communication the board had indicated that inventive step based upon D1 in combination with D13 might be discussed at the oral proceedings, and hence the patent proprietor could have foreseen that the argument which the opponent was now relying on might well become a subject for discussion. Documents D1 and D13 had both been before the opposition division and had been extensively discussed throughout the proceedings.

In T 161/09 the board decided to use its discretionary power to admit the appellants' first line of argument to the proceedings, in support of their objection of lack of inventive step, despite these submissions having been made only during the oral proceedings and having been contested as being inadmissible by the respondent. In the view of the board these submissions did not alter the legal and factual framework of the proceedings. In T 112/13, too, the board admitted a more detailed and expanded line of argument at the oral proceedings under Art. 13(1) RPBA 2007 because it did not substantially amend the case as set out in its statement setting out the grounds of appeal.

Likewise in T 671/08 the late filed argument was exceptionally admitted despite causing adjournment of the oral proceedings. The board considered the appellant's (opponent's) objection of insufficient disclosure to be a fundamental one that could not be ignored. The board stated that the fundamental nature of the new objection would render any discussions on novelty and inventive step meaningless, had it been left unresolved. This case was an exception to the principles set out in Art. 13(3) RPBA 2007 where amendments to a party's case should not be admitted into the proceedings when their admission would lead to an adjournment of the oral proceedings.

In T 524/12 the case made by the appellant (opponent) was an extension of the case it had made before the opposition division. Since, in essence, similar features were discussed, and the lines of argument put forward were largely those that had already been discussed, the appellant was not making a substantially new case, but was simply basing the case it had made in support of its objection before the opposition division partly on new arguments. Art. 12(4) RPBA 2007 did not provide for not admitting mere arguments.