The legal concept "fresh ground for opposition" as used in G 10/91 (OJ 1993, 420, point 18 of the Reasons) must be interpreted as having been intended to refer to a ground for opposition which was neither raised and substantiated in the notice of opposition, nor introduced into the proceedings by the opposition division. In a case where a patent had been opposed on the grounds set out in Art. 100(a) EPC, but the opposition had only been substantiated on the grounds of lack of novelty and lack of inventive step, the ground of unpatentable subjectmatter based on Art. 52(1) and (2) EPC was a fresh ground for opposition and accordingly could not be introduced into the appeal proceedings without the agreement of the patentee (G 1/95, OJ 1996, 615). In a case where a patent had been opposed under Art. 100(a) EPC on the ground that the claims lacked an inventive step in view of documents cited in the notice of opposition, the ground of lack of novelty vis-à-vis the said documents based on Art. 52(1) EPC 1973 and Art. 54 EPC was a fresh ground for opposition and accordingly could not be introduced into the appeal proceedings without the agreement of the patentee. However, the allegation that the claims lacked novelty in view of the closest prior art document could be considered in the context of deciding on the ground of lack of inventive step (G 7/95, OJ 1996, 626).
In T 1549/07, the ground for opposition under Art. 100(b) EPC had not been raised until after expiry of the opposition period and therefore had to be considered late filed. The opposition division had admitted the new ground to the proceedings without stating its reasons for doing so. It had then rejected the opposition and maintained the patent as granted. The patent proprietor/respondent requested that the board refrain from examining the ground under Art. 100(b) EPC in the appeal proceedings.
The board found that, while the opposition division's inadequately reasoned decision constituted a procedural error, the patent proprietor had not objected to it at any time during the oral proceedings. Nor had it led in the course of the opposition proceedings to any final decision adversely affecting the patent proprietor. The board thus deemed the patent proprietor's request that the board refrain from examining the ground for opposition under Art. 100(b) EPC on appeal inadmissible and refused it. There were no EPC provisions under which a ground for opposition admitted to and examined during the proceedings could be eliminated at the appeal stage. Since, in the case at issue, the opposition division had decided to admit the ground for opposition under Art. 100(b) EPC, it had become part of the contested decision and, as a result, was not "a fresh ground for opposition" introduced on appeal within the meaning of the opinion in G 10/91. The board therefore had no need to obtain the patent proprietor's consent to the introduction of the ground for opposition under Art. 100(b) EPC and was entitled to consider that ground further.