A decision by a board of appeal on an appeal from an examining division decision is not binding in subsequent opposition proceedings or on appeals therefrom, having regard both to the EPC and to the principle of res judicata (T 167/93, OJ 1997, 229). The binding effect is also not restricted to cases where the composition of the board remained unchanged (T 436/95). Following T 167/93, the board in T 1099/06 pointed out that opposition proceedings are separate and distinct from examination proceedings and are characterised by the nature of the public interest. The legislative and procedural framework has quite clearly been designed to allow the public interest in challenging granted patents by opposition to take priority over any considerations of certainty or apparent consistency. The board pointed out that to the extent this principle is recognised in the law of the EPC, it is of extremely narrow scope and must meet the six criteria set out in T 167/93 (OJ 1997, 229) - the issue must have been (a) judicially determined; (b) in a final manner, (c) by a tribunal of competent jurisdiction; (d) where the issues of fact are the same; (e) the parties (or successors in title) are the same; and (f) the legal capacities of the parties are the same. Thus a decision in earlier examination appeal proceedings could not be res judicata in subsequent opposition appeal proceedings, the criteria (c), (e) and (f) not being satisfied.
Under Art. 111(2) EPC 1973, if a board of appeal remitted a case for further prosecution to the department whose decision was appealed, that department was bound by the ratio decidendi of the board in so far as the facts were the same. After grant, however, the opposition division was in no way legally bound by the previous decision of the board, on an appeal from the examining division, even in so far as the facts were the same, although it should not deviate from a previous decision of a board of appeal on such a point, unless there appeared to be very clear reasons for doing so (T 26/93).