In T 166/04 the examining division had refused the patent application at the end of oral proceedings which the applicant had not attended. In the appellant's opinion, a gross procedural violation had occurred in that the examining division had used a short-term invitation to oral proceedings to introduce additional prior art documents in a complex technical field. The examining division should have issued another communication to safeguard the applicant's right to be heard. The board held that even if the prior art documents had formed part of a critical argumentation, their late introduction was not necessarily improper. Apart from the non-extendable time limit, the appellant had had an opportunity to respond to the summons in writing as if he had responded to a communication under Art. 96(2) EPC 1973, which he had actually done by submitting amendments and further arguments. In addition, the board pointed out that the applicant had decided not to participate in the first-instance oral proceedings in the course of which he could have made further submissions.
In T 515/05 the appellant had based its opposition only on the grounds of Art. 100(a) EPC 1973, but in the summons to the oral proceedings the opposition division itself introduced a further ground for opposition under Art. 83 EPC 1973, Art. 100(b) EPC 1973. The chairman of the opposition division stated at the beginning of the oral proceedings that no discussion of the ground of opposition according to Art. 100(b) EPC 1973 would take place, because this opposition ground had not been sufficiently substantiated by the opponent. The board considered that this constituted a substantial procedural violation. The fact that the appellant did not avail itself of the opportunity to file written arguments in response to the summons to attend the oral proceedings did not deprive it of its right to be heard. The appellant was entitled to expect that it would still have an opportunity to comment on this new ground during the oral proceedings.