The question of whether a party has discharged its onus of proof in relation to the availability to the public of a document is an argument and not a new ground of appeal. The prohibitions or restrictions on additions to the extent to which a patent is opposed, the raising of a new ground for opposition or the introduction of new facts or evidence, do not apply to the admission of a new argument. Indeed, the very purpose of appeal proceedings, particularly oral proceedings, is to provide an opportunity for a losing party to throw new light on relevant aspects of matters which have been decided to his detriment and/or to draw attention to facts in the reasoning of the department of first instance that resulted in a decision adverse to him. This can, in practice, best be achieved by reliance on new arguments. Whilst it is desirable that all relevant arguments be brought at the earliest possible stage of the proceedings, there is no requirement in Art. 108 EPC 1973 that the statement of grounds of appeal be exhaustive as to the arguments to be brought (T 86/94).
Similarly, in T 432/94 the appellant was allowed to redefine the problem to be solved by the invention. The board stated that it could not be concluded from Art. 108, third sentence, EPC 1973 that an appellant was bound to the line of argument he used in the statement of grounds for the whole appeal proceedings; this dealt with an admissibility requirement and did not limit the matter in dispute in appeal proceedings.