5. Standard of proof for allowing amendments and corrections

In accordance with the established jurisprudence of the boards of appeal of the EPO, 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". This is taken from T 1248/08, in which the board recalled this case law, in particular as established in T 113/86, point 2.2 of the Reasons; T 383/88 of 1 December 1992, point 2.2.2 of the Reasons; T 581/91 of 4 August 1993, point 3 of the Reasons, last three paragraphs; T 723/02 of 13 May 2005, point 2.4 of the Reasons; and T 1239/03 of 2 November 2006, point 3.3.3 of the Reasons.

In T 383/88 the board held that the normal standard of proof in proceedings before the boards of appeal, 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.

It had frequently been argued that certain technical features could be directly and unambiguously derived from a specification as filed by reading it in the light of common general knowledge. However, the board recommended viewing this approach with considerable caution. Firstly, 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. Secondly, 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. Furthermore, too much reliance could not be placed on affidavit evidence from over-qualified persons, for the relevant knowledge was that of a notional, i.e. average, skilled addressee, and not that commanded by leaders in the relevant scientific discipline or field. The board added that it could not normally be the case that an affidavit by a single person was sufficient to discharge the burden of proof to the strict standard that was required (quoting T 383/88 in this respect see also T 1046/96, T 1239/03, T 1006/03).

In T 581/91 the board held that the balance of probabilities was not an appropriate criterion to be applied in a case where a correction under R. 88 EPC 1973 was at stake. Following decision T 383/88, the board stated that a more rigorous standard, that is one equivalent to "beyond reasonable doubt", ought to be applied.

In T 795/92 the board stated that Art. 123(2) EPC 1973 clearly precluded allowing an amendment if there was any doubt as to whether or not it was derivable from the original application. In the case at issue an upper limit of 89% indicated in claim 1 of the main request for the degree of nickel reduction was not expressly mentioned in the application as filed. The board decided that, in spite of a certain probability in favour of the appellant/patentee's position, the amendment was not allowable because there were various known methods for calculating this value, not all leading to identical results, and the application did not directly and unambiguously disclose which method had to be used.

The board in T 307/05 stated that, as indicated in the decision T 64/03 of 1 February 2005 (points 3 and 3.1 of the Reasons), it is established case law that a very rigorous standard, namely that of "beyond reasonable doubt", is 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. While it was true that, as argued by the appellant, decision T 113/86 referred to voluntary amendments requested by the patentee and not necessitated by any ground of opposition, the fact that the amendment would be, as in the present case, necessitated by a ground of opposition (i.e. Art. 100(c) EPC) could not, in the board's view, justify the application of a lower standard of proof than the one mentioned in that decision. On the contrary, a very rigorous standard was even more justified in the case in question, since allowing such amendments while using a lower standard of proof might give an unwarranted advantage to the patentee in the overcoming of a ground of opposition. The board also said that it could not be deduced from the decision T 166/90 relied on by the appellant that a lower standard of proof could be applied when checking the allowability of amendments.

In T 1248/08, in the application as filed, a number pertaining to a value used in example 1 was illegible and indecipherable. It was not clear whether it should read "0.08" or "0.09", or even "0.05". The board was not persuaded by the appellant's arguments that the actual disclosure of that figure was unequivocal and that it read "0.09".

Having considered the settled case law (as cited in the introduction to this section), the board held that the arguments of the appellant adopting proof "on the balance of probability", in particular a survey in favour of the value of "0.09", had to fail. According to this survey - conducted amongst partners and staff at the firm of the appellant's representative - a total of 67 out of 72 test persons had indicated the relevant entry in Table 1 to be "0.09" without qualification. However, it was also found that two respondents had indicated another figure ("0.08") and that three further respondents who indicated "0.09" had also considered other possibilities. In the board's opinion, therefore, these results demonstrated that the value in question could not be considered to be "0.09" with a certainty "beyond reasonable doubt", as required by the established jurisprudence. In any event, a question of accuracy and disclosure could not be decided by a poll.

The appellant had also pointed to the priority document of the patent in suit and to the family patent document as potential sources of supplementary original disclosure. This approach had to fail, because of G 11/91 (point 7 of the Reasons). The board therefore decided that the disclosure of the priority document could not be used to supplement or replace parts of the disclosure of the application as originally filed. Nor could it be used to dispel doubts as to the meaning of an ambiguous part of the application. The same applied to the family documents, for the reason that the text of another patent application based on the same priority document did not need to be identical to the European patent application.

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