T 60/89 (OJ 1992, 268) held that when alleged facts put forward without proof as causing lack of novelty had occurred a long time previously and the question was no longer pursued by the parties it was not obliged to investigate the matter ex officio under Art. 114(1) EPC 1973. Nor did the board in T 505/93 consider itself obliged to carry out any further investigation when the opponents refused to take part in oral proceedings where the content of a prior use was to be clarified.

In the context of an appeal by an appellant (opponent) from an opposition division decision maintaining the patent in amended form, the board of appeal only has to consider the appeal as regards claims upon which the appellant (opponent) has advanced arguments and those claims that are dependent, either wholly or partially, on these claims, and has to apply the provisions of Art. 114(1) EPC 1973 in a restricted manner (T 223/05).

The board in T 2501/11 stated in its catchword: where prior publication of a citation has been admissibly disputed and the party bearing the burden of making the case for and proving it fails to provide a substantiated response, the board cannot treat that citation as prior art because opposition appeal proceedings are adversarial and so conducted in accordance with the adversary system of procedure, in which it is for the parties to make their cases and the boards' power to examine the facts of their own motion (Art. 114(1) EPC) is limited.