5. Evidence and standard of proof for allowing amendments and corrections

In accordance with the established case law of the boards of appeal, in the case of a proposed amendment under Art. 123(2) EPC or of a correction under R. 139 EPC, the factual disclosure of a European patent application as originally filed has to be established to a rigorous standard, namely the standard of certainty "beyond reasonable doubt". In T 1248/08 the board recalled this case law, in particular as established in T 113/86, T 383/88, T 581/91, T 723/02 and T 1239/03; for further recent decisions confirming this standard, see e.g. T 831/11, T 1710/13, T 2418/13, T 1224/14, T 19/20, J 3/21, T 1435/20 and T 1515/20. In particular, the board observed in T 768/20 that the very requirement of an unambiguous disclosure under the "gold standard" indicated that a strict standard had to be applied and that the actual existence of a disclosure was not a matter of probabilities.

According to T 307/05 and T 370/10, the same standard of "beyond reasonable doubt" applies when assessing the allowability of amendments under Art. 123(3) EPC. For further decisions confirming this standard, see e.g. T 2275/17.

The burden of proof that amendments comply with Art. 123(2) EPC rests with the party making the amendment (T 910/06 with reference to T 1239/03; see also T 222/05 and T 1497/08). See T 2275/17 in the context of Art. 123(3) EPC.

In T 383/88 the board held that the normal standard of proof in proceedings before the boards, namely "the balance of probability", was inappropriate for determining the allowability of an amendment under Art. 123(2) EPC 1973. Instead, a rigorous standard, i.e. one equivalent to "beyond reasonable doubt" was considered by the board to be the right one to apply in such a case, since applying a lower standard could easily lead to undetected abuse by allowing amendments on the basis of ostensibly proven common general knowledge. T 383/88 also considered that the issue of the allowability of an amendment under Art. 123(2) EPC 1973 had to be decided by reference to what could be derived from the patent application as filed in the light of common general knowledge and not vice versa. Moreover, it was notoriously difficult to prove common general knowledge. For example, information might be generally disseminated, and therefore known within the community of skilled addressees, but it might well, at the same time, not be commonly accepted.

The board in T 307/05 stated that, as indicated in the decision T 64/03, it was established case law that a very rigorous standard, namely that of "beyond reasonable doubt", was to be applied when checking the allowability of amendments under Art. 123(2) and 123(3) EPC. A similar rigorous standard was also expressed in the decision T 581/91 relied on by the board in its communication by reference to the decision T 113/86, in which it was stated that the slightest doubt that the unamended patent could be construed differently to the patent as amended would preclude the allowability of the amendment (see also T 370/10, T 2285/09, T 2418/13).