3.3.1 General

G 2/21 (OJ 2023, A85), point 32 of the Reasons summarises the earlier case law as follows: "The principle of free evaluation of evidence may not be used to disregard evidence per se insofar as it is admissibly submitted and relied upon by a party in support of an inference which is challenged and is decisive for the final decision. Disregarding it as a matter of principle would deprive the party submitting and relying on such evidence of a basic legal procedural right generally recognised in the EPC contracting states and enshrined in Art. 113(1) and 117(1) EPC (see also T 1110/03, point 2 of the Reasons, T 1797/09, point 2.9 of the Reasons, T 419/12, point 2.1.3 of the Reasons, and T 2294/12, point 1.1.3 of the Reasons)".

In T 1110/03 (OJ 2005, 302) the board had observed that Art. 117(1) and 113(1) EPC embody a basic procedural right generally recognised in the EPC contracting states, viz. the right to give evidence in appropriate form (specifically by producing documents under Art. 117(1)(c) EPC) and the right to have that evidence heard (T 1110/03) to the extent that it has not been expressly excluded from the debate (T 2294/12).

EPO departments must ascertain the relevance of evidence submitted to them before deciding to admit or reject it. Only in exceptional circumstances need they not to do so (T 142/97, Catchword). An opposition division's refusal to consider evidence filed in due time infringes a party's fundamental right to free choice of evidence and the right to be heard (T 142/97, OJ 2000, 358). See also T 1231/11 (citing T 267/06, T 448/07, T 25/08), according to which the offered witness has to be summoned should any doubt remain.

Furthermore, pursuant to Art. 113(1) EPC each party must be allowed to comment on any evidence legitimately submitted in the proceedings. Allowing one party, even the party that originally submitted the evidence, to require unilaterally and arbitrarily that the evidence be withdrawn or excluded from consideration would infringe this right (T 95/07; cf. the case in T 760/89, OJ 1994, 797, concerning a return of documents filed as evidence).

As a rule, if assertions made in an unsworn witness declaration ("eidesstattliche Versicherung") remain contested, a request from a party to hear the witness must be granted before these assertions are made the basis of a decision against the contesting party. In T 474/04 (OJ 2006, 129) the opposition division had revoked the patent in suit because the invention did not involve an inventive step over the prior use evidenced in the declaration in lieu of an oath. Since fundamental assertions made in the declaration had been contested, the author was offered as a witness. Although the appellant (patentee) had consistently demanded that the author be heard, the opposition division decided not to summon him as a witness, even though he was available. In the board's view, the appellant had effectively been prevented from making use of a decisive piece of evidence (decision T 474/04 extensively cited in T 190/05, which in turn is frequently cited, including more recently in T 2659/17, G 2/21 and T 778/21, for example).

Failure to consider evidence will normally constitute a substantial procedural violation in that it deprives a party of basic rights enshrined in Art. 117(1) and 113(1) EPC (T 1098/07). In T 135/96 (point 3 of the Reasons), ignoring documents (and arguments) relevant to inventive step was found to violate the party's right to be heard. The board in T 1110/03 (OJ 2005, 302) made a similar finding where indirect evidence substantiating an allegation of fact relevant to novelty was disregarded. In T 1536/08 the opposition division had infringed the opponent's right to be heard by completely ignoring the unambiguous offer in its notice of opposition to provide the original printed versions of crucial prior art documents (see also chapter III.B.2.5.5 "Failure to consider evidence").

For an overview of the case law, see T 1738/21 (particularly points 2.1.5 and 2.1.11 of the Reasons), summarised in chapter III.G.3.3.4; see also chapter III.G.3.1.2.