4.2. Probative value of evidence on a case-by-case basis

According to the principle of free evaluation of evidence, each piece of evidence is given an appropriate weighting according to its probative value. As the Enlarged Board pointed out in G 3/97 (OJ 1999, 245, point 5 of the Reasons) and G 4/97 (OJ 1999, 270, point 5 of the Reasons), "(t)he principle of free evaluation would be contradicted by laying down firm rules of evidence defining the extent to which certain types of evidence were, or were not, convincing" (cited in G 1/12, OJ 2014, A114). Also confirmed in G 2/21 (OJ 2023, A85), according to which: "Free evaluation of admissibly filed evidence relevant for deciding the case at hand means that there are no firm rules according to which certain types of evidence are, or are not, convincing" (point 34 of the Reasons).

With regard to the boards' review of the evaluation of evidence at first instance, the applicable law appears to be established by T 1138/20, which largely endorsed the principles set out in T 42/19 (see in this chapter III.G.4.2.2b)); the issue had indeed already been debated in T 1418/17, T 1604/16 and T 42/19.

The following cases illustrate how the boards have evaluated various pieces of evidence in the light of the specific circumstances.