4.2.1 Ranking of means of evidence

In recent decision T 1138/20 the board stated that evidence was assessed in accordance with the principle of the free evaluation of evidence, which also meant that the means of taking evidence listed in Art. 117 EPC was not set out hierarchically. T 1138/20 brings together various developments to the principles deriving from the law of evidence (largely by reference to earlier case law). In its detailed reasons, however, it also applies them to the case at issue and, in doing so, illustrates the consequences of not ranking evidence. The board considered that the allegation that the opposition division had given more weight to the witnesses' testimonies than to the documentary evidence on file was, as such, insufficient for reversing the opposition division's findings of fact. It could generally not be considered an error if more weight is given to a witness testimony than to the documentary evidence on file. The mere fact that the opposition division decided that a fact was corroborated by the witness testimony, and was thus proven, even though the documentary evidence on file was actually not sufficient to prove that fact or was even contrary to the witness testimony, did not mean that there had been an error in the assessment of the evidence. See also point 1.2.3 of the Reasons for the decision on the scope of the required reasoning where there is contradictory evidence.

The board in T 2659/17 observed (with reference to T 474/04) that an affidavit carried less weight than testimony. It found, therefore, that decisions should not be based solely on an affidavit, but rather the person who had made it should be heard as a witness whenever offered by a party. This applied all the more in the case in hand since the patent proprietor had challenged the content of the affidavits and demanded that the offered witnesses be heard. Denying it the opportunity to question those witnesses had prevented it from rebutting the ultimately crucial evidence. This was even more serious given that evidence for the prior use lay largely within the power and knowledge of the opponent (violation of Art. 113(1) EPC). See also T 329/02 in this chapter III.G.3.3.4. See also T 1604/22 on the probative value of affidavits considered by the board, bearing in mind that the witnesses in the case were heard at first instance (by videoconference).

In T 918/11, the board held that a mere reference to the fact that testimonies B1 and B2 concerned facts which had occurred at least 14 years ago and that other documentary evidence might possibly exist did not suffice in the case in hand to dismiss the testimonies as insufficient. It went against the general rules concerning the consideration of evidence to distinguish dogmatically between the evidentiary value of a witness testimony on the one hand and a document on the other hand. The opposition division had apparently considered documents to be of a more conclusive evidentiary value than witnesses. Such an approach had no basis in the EPC, Art. 117 EPC containing no ranking of the means of evidence it listed (see also T 2565/11, in which it was similarly found that witness testimony and documents were not ranked in this way).

See also in this chapter III.G.2.4.1d) and III.G.2.5.4.