4.1. Principle of free evaluation of evidence

Neither in the EPC nor in the case law of the board of appeal are formal rules laid down for the evaluation of evidence (reaffirmed in G 2/21, OJ 2023, A85, point 47 of the Reasons, before analysis of the law of the contracting states under Art. 125 EPC). The Enlarged Board of Appeal has recalled many times that proceedings before the EPO are conducted in accordance with the principle of the free evaluation of evidence (G 1/12, OJ 2014, A114, citing G 3/97, OJ 1999, 245, point 5 of the Reasons; and G 4/97, OJ 1999, 270, point 5 of the Reasons), which it reaffirmed in the more recent G 2/21 (point 29 of the Reasons). The decision being largely devoted to this point, the principles set out and confirmed there are reported below in a separate subsection.

The EPO departments have the power to assess whether the alleged facts are sufficiently established on a case-by-case basis. Under the principle of free evaluation of evidence, the respective body takes its decision on the basis of all of the evidence available in the proceedings, and in the light of its conviction arrived at freely on the evaluation whether an alleged fact has occurred or not (see e.g. T 482/89, OJ 1992, 646; T 592/98, T 972/02; see also e.g. T 838/92, in which the board found there was a detailed and consistent body of evidence establishing that a device had been on sale before the patent application was filed). See also G 2/21, point 34 and T 1138/20 point 1.2.2 of the Reasons.

However, the principle of free evaluation of evidence in EPO proceedings cannot go so far as to justify the refusal of a relevant and appropriate offer of evidence. Free evaluation of evidence means that there are no firm rules according to which certain types of evidence are, or are not, convincing. The deciding body must take all the relevant evidence before deciding whether or not a fact can be regarded as proven (T 474/04, OJ 2006, 129, citing G 3/97, OJ 1999, 245, point 5 of the Reasons – see also G 2/21, point 34 and T 1138/20 point 1.2.2 of the Reasons, which talk of a "decision on the basis of all the relevant evidence available in the proceedings"). On the other hand, failure to submit evidence despite a board's request to do so may be viewed as a sign that the evidence would perhaps not confirm what has been claimed (see T 428/98, OJ 2001, 494).

Ruling on a refusal to hear witnesses, the board in T 1363/14 held that the principle of free evaluation of the evidence did not apply until after it had been taken and could not be used to justify not taking evidence offered. This was confirmed in G 2/21, point 44 of the Reasons, which also cites T 2238/15; see also in this chapter III.G.2.2.

In J 14/19 (stay of the proceedings) the board explained that the EPO did not have any discretion when deciding on a stay of proceedings under R. 14(1) EPC. If a third party demonstrated that the requirements in R. 14(1) EPC were met, the proceedings for grant had to be stayed. This was not the same as deciding whether the factual requirements for a stay under R. 14(1) EPC were indeed met, which was not a matter of discretion but a question of evaluating the evidence. The latter saw the decision-making body examine the evidence to decide whether it was satisfied that the claimed facts were correct (see G 1/12, OJ 2014, A114). If it considered that a pivotal fact had not been established, it could order that more evidence be submitted under Art. 114(1) EPC.