As the Enlarged Board made clear in G 8/93 (OJ 1994, 887), the board's obligation under Art. 114(1) EPC 1973 existed only once proceedings were pending (see also T 690/98). Earlier, T 328/87 (OJ 1992, 701) had already ruled that the facts could be investigated only if the appeal was admissible. There were, however, limits to this obligation, for example under Art. 114(2) EPC 1973, where facts and evidence are submitted late. The same applied if an opponent (respondent) withdraws his opposition: in T 34/94 the board found that, "if in the event of withdrawal of the opposition the opponent is the respondent, the board may take into account evidence which was submitted by the opponent prior to withdrawal of the opposition. However, for reasons of procedural economy, the duty of the EPO to examine the facts of its own motion does not extend to its having to examine the submission of the opponent that a previous oral disclosure took place if the crucial facts were difficult to ascertain without his co-operation" (this confirmed the case law in T 129/88, OJ 1993, 598; T 830/90, OJ 1994, 713; T 887/90, T 420/91 and T 634/91; see also T 252/93 and T 1047/03).
In T 1574/11 the board observed that it was not restricted to the facts, evidence or arguments provided by the parties. As the primary purpose of the appeal procedure was to check that the contested decision was correct, the board was in principle entitled to consider the evidence provided therein if it deemed it to be relevant to its own decision.
T 182/89 (OJ 1991, 391) sets out what the obligation to investigate involves; Art. 114(1) EPC 1973 should not be interpreted as requiring the opposition division or board of appeal to ascertain whether there was support for grounds for opposition not properly substantiated by an opponent, but as enabling the EPO to investigate fully the grounds for opposition which were both alleged and properly substantiated pursuant to R. 55(c) EPC 1973 (see also T 441/91 and T 327/92). In T 263/05 (OJ 2008, 329) the board accepted that it had an ex officio duty under Art. 114(1) EPC 1973 to examine amended claims, but only for prima facie non-compliance with the EPC, e.g. lack of clarity or conciseness.
If departments of first instance and/or parties fail to take account of highly relevant matter which is clearly available in the EPO file and which relates to a ground of opposition, the board's competence extends to rectifying the position by consideration of that matter provided, of course, the parties' procedural rights to fair and equal treatment are respected. This is not only consistent with decisions G 9/91 (OJ 1993, 408) and G 10/91 (OJ 1993, 420), but incumbent on the board as the last instance in proceedings concerning the grant or maintenance under opposition of European patents (T 385/97). It enhances acceptance of the boards' decisions and their standing as the only judicial body ruling on patentability with effect for all the designated contracting states, if those decisions based on all material are submitted during the appeal proceedings. A document presented in such proceedings should therefore be taken into account if it is not completely irrelevant or at odds with considerations of procedural economy (T 855/96).