1. Introduction

The main provisions governing evidence, the means and taking of evidence and the conservation of evidence are Art. 117 EPC, Art. 131(2) EPC, R. 117 EPC (R. 117 and 118 EPC were amended by decision CA/D 12/20 of the Administrative Council of 15 December 2020, OJ 2020, A132, which entered into force on 1 January 2021) to R. 124 EPC (the last rule as amended by decision CA/D 6/14 of the Administrative Council (OJ 2015, A17), which entered into force on 1 April 2015) and R. 150 EPC. R. 117 and 118 EPC as amended in 2020 relate to means of taking evidence by videoconference (decision T 423/22 dealt explicitly with a witness hearing by videoconference before the opposition division); compare with new Art. 15a RPBA, which entered into force in 2021 (OJ 2021, A19), and G 1/21 date: 2021-07-16 of 16 July 2021 date: 2021-07-16 (OJ 2022, A49).

In the revised EPC 2000, the content of Art. 117(2) to (6) EPC 1973 was rephrased in the new Art. 117(2) EPC. The procedural aspects concerning the taking of evidence were transferred to the Implementing Regulations (see OJ SE 5/2007, Part II, pp. 176-192). Furthermore, the revised Art. 117(1) EPC no longer lists the EPO departments which may take evidence; it now includes a general reference to "proceedings before the European Patent Office".

Art. 117 EPC, entitled "Means and taking of evidence", provides for the submission of evidence before all EPO departments, including the Receiving Section, examining divisions, opposition divisions, the Legal Division and the boards of appeal.

Beyond the letter of the EPC, the boards of appeal have addressed multiple issues of admissibility and taking of evidence in their case law. In addition, they have elaborated specific principles governing the evaluation of evidence and the allocation of the burden of proof in order to ensure that EPO proceedings are conducted in a fair and consistent manner.

Issued since the last edition 2022 of this book, decisions G 2/21 (OJ 2023, A85) and T 1138/20 summarise and confirm these principles established by the boards' case law as applying to the handling of evidence in both first-instance and appeal proceedings before the EPO, setting them out much more clearly than ever before.

G 2/21 (OJ 2023, A85) includes detailed findings on the principle of free evaluation of evidence (in particular in points 27 to 46, 55 and 56 of the Reasons) and also confirms that submitted evidence may not be disregarded solely on the ground that such evidence had not been public before the filing date of the patent in suit and was filed after that date (point 56 of the Reasons).

T 1138/20, which cites G 2/21, is devoted almost entirely to matters of evidence and elaborates on a number of concepts and the interplay between them. These include the applicable standard of proof, the principle of free evaluation of evidence and its consequences, the reviewing findings of facts on appeal, the scope of reasoning, the burden of proof on appeal and the extent of the boards' powers. T 1138/20 also clearly lays out certain principles, with the main findings being recapitulated in the catchword.

As G 2/21 and T 1138/20 are therefore reported extensively in this chapter, it is worthwhile reading the decisions issued in those in full.

However, this introduction also covers a number of principles deriving above all from older other decisions of the boards.

In T 2037/18, the board explained that in most legal systems and in proceedings before the EPO (beyond the area open to examination by the EPO of its own motion), the burden of presentation and the burden of proof were allocated such that each party had to present and prove the facts that were favourable to them, i.e. the facts that supported their own assertions (T 219/83, T 270/90). According to the board, the principle of "negativa non sunt probanda", recognised in the boards' case law (see R 15/11, R 4/17), was a clear expression of this allocation of the burden of proof. In other words, a party to the proceedings was not required to prove a negative fact, but rather it was incumbent on the opposing side to prove any positive fact favourable to them. As a general rule, the burden of presentation followed the burden of proof. See also T 1076/21.

In accordance with the principle of free evaluation of evidence, any kind of evidence, regardless of its nature, is admissible (T 482/89, OJ 1992, 646). Parties can freely choose the evidence they wish to submit – the kinds listed in Art. 117(1) EPC are merely examples (T 543/95, T 142/97, OJ 2000, 358). This principle of free evaluation of evidence was reaffirmed in G 2/21, points 40 and 41 of the Reasons, while the freedom to produce evidence of one's own choosing was reiterated in T 1138/20 (points 1.3.4(a) and (b) of the Reasons).

That proceedings before the EPO are conducted in accordance with the principle of free evaluation of evidence was reiterated by the Enlarged Board (G 1/12, OJ 2014, A114, and confirmed and elaborated on in G 2/21, OJ 2023, A85, points 27 to 46 of the Reasons).

Art. 117(1) EPC and Art. 113(1) EPC embody a basic procedural right, viz. the right to give evidence in appropriate form and the right to have that evidence heard (T 1110/03, OJ 2005, 302). A decision should discuss the facts, evidence and arguments which are essential to the decision in detail (see for example T 278/00, OJ 2003, 546, in chapter III.K.3.4.4 b)). This too was reaffirmed in G 2/21, points 41 and 42 of the Reasons, and similarly recapitulated in T 1738/21, point 2.1.11 of the Reasons.

Whether or not a fact can be regarded as proven has to be assessed by the department hearing the case having taken all the relevant evidence into consideration (T 474/04, OJ 2006, 129 and T 545/08 citing G 3/97, OJ 1999, 245, point 5 of the Reasons; as reiterated in G 2/21, in particular points 30-32, 34 of the Reasons, and even more recently in T 1138/20, point 1.2.2 of the Reasons and the Catchword). As with any other findings of a deciding body, a finding of fact must be reasoned (T 1138/20, with reference to G 2/21, point 31 of the Reasons). This is particularly important if there was contradictory evidence on file. Then, the process of weighing the different pieces of evidence must be properly reflected in the reasoning of the final decision (T 1138/20, point 1.2.3 of the Reasons – on the scope of the required reasoning, see also the findings on a "plausible alternative" in points 1.3.4(c) and 1.3.8 (last paragraph) of the Reasons and on the duty to provide reasons in point 1.2.6 of the Reasons). Likewise on the scope of the reasoning, see G 2/21 (points 31 and 41 of the Reasons) and T 42/19 (point 3.5 of the Reasons); on refusing an offer of evidence, see T 1647/15 and T 1738/21.

If the evidence offered as proof of contested facts essential to the settlement of the dispute is decisive, the department hearing the case must, as a rule, order that it be taken (T 474/04, OJ 2006, 129; about witnesses, see also T 2659/17). All appropriate offers of evidence made by the parties should be taken up (T 329/02). See also G 2/21, point 32 of the Reasons.

The principle of unfettered consideration of the evidence does not apply until after it has been taken and cannot be used to justify not taking evidence offered (T 2238/15, alleged prior use – offer of witnesses; see also the principles laid down in T 1363/14). This principle was reaffirmed in G 2/21, points 44 and 56 of the Reasons.

As regards the handling on appeal of evidence that was admitted in the first-instance proceedings, the EPC does not provide a legal basis for excluding, in appeal proceedings, documents which were correctly admitted into the first-instance proceedings, in particular when the impugned decision is based on them (T 1201/14, T 26/13, T 931/14, T 564/12; see also T 95/07, point 4.2.12 of the Reasons, T 1277/12 of 7 April 2017 date: 2017-04-07, and more recently T 110/18, T 617/16, T 3234/19, T 487/16 (with reference to the RPBA 2007 and the RPBA 2020), T 1884/19, T 2049/16, with detailed reasons (cited more recently in T 1983/19, which took the same approach), T 1634/17, T 1738/21 (and decisions cited there); for the issue in general, see in particular chapter V.A.3.4.4 "Submissions admitted at first instance are part of the appeal proceedings"). Compare with the nuanced approach taken recently in T 960/15 (cited in T 2035/16, T 2742/18 and T 1193/21; not followed in T 1206/19). And on the question of the admissibility of evidence submitted by the intervener, including the reintroduction of certain evidence originally submitted by a party but not admitted as late, see T 2951/18.

T 1138/20 ("Reviewing findings of fact") clarified that the boards have the power, at any stage of the appeal proceedings, to establish the relevant facts of the case before them and thereby substitute the findings of fact made by the departments of first instance. However, the boards have no obligation to establish de novo facts already established by the departments of first instance (T 1138/20, Catchword 2 and point 1.2.4 of the Reasons, which refers to T 42/19). The review of findings of fact simply has nothing to do with the review of discretionary decisions. Discretionary decisions can only be reviewed for a particular type of error (G 7/93, point 2.6 of the Reasons), while a review of findings of fact has no such limitation (T 1138/20, point 1.2.4 of the Reasons). In this chapter III.G.4.2.2 b), reviewing findings of fact is dealt with in the context of witnesses, but it is also relevant for documents (see, inter alia, T 1138/20 , point 1.2.4(c) of the Reasons).

As for the standard of proof, the EPO generally applies the "balance of probabilities" (see J 20/85, OJ 1987, 102, point 4 of the Reasons). The balance of probabilities standard is met if, after evaluating the evidence, the boards are persuaded one way or the other (T 286/10). However, especially in cases where only one party – the opponent – had access to information about an alleged public prior use, the case law has tended toward expecting that the public prior use be proved beyond any reasonable doubt or "up to the hilt" (see e.g. T 55/01, point 4.1 of the Reasons; and T 472/92, OJ 1998, 161, point 3.1 of the Reasons; T 2451/13, Catchword). A summary of the case law concerning the standard of proof can be found e.g. in the following cases: T 738/04, point 3.4 of the Reasons; T 286/10, point 2.2 of the Reasons; T 918/11, point 3.3 of the Reasons; T 2054/11, points 2.2 and 2.3 of the Reasons; T 2227/11, point 2 of the Reasons; T 274/12, point 4.2.1 of the Reasons; T 202/13, point 15.6.1 of the Reasons; T 2451/13, point 3.2 of the Reasons; T 545/08, points 7-11 of the Reasons.

More recently, the board in T 1138/20, having considered the past case law, clearly stated that there was only one standard of proof in the proceedings before the EPO: the deciding body, taking into account the circumstances of the case and the relevant evidence before it, had to be convinced that the alleged fact had occurred. If only the opponent had had access to the relevant evidence, this fact had to be given due consideration in the deciding body's assessment as to what weight and importance to attach to such evidence. According to the board in T 1138/20, this was not the same as saying that a different standard of proof should apply.

The standard of proof for internet citations seems to have been established by the decisions in T 286/10 and T 2227/11, which were endorsed in T 1711/11, T 353/14 and T 545/08. The appropriate standard of proof for internet citations is the "balance of probabilities". The conclusion reached in the earlier decision T 1134/06 (followed by T 19/05 and T 1875/06) that the stricter standard of proof "beyond reasonable doubt" had to be applied to internet disclosures has been refuted.

Examining the evidence a board took into account would amount to revisiting the substance of the case and so falls outside the ambit of the review procedure (R 21/09, R 6/12). A reversal of the burden of proof is not covered by the exhaustive list of possible grounds for a petition for review (R 21/10).

R. 3(3) EPC provides that documentary evidence may be filed in any language. The EPO may, however, require that a translation in one of its official languages be filed within a specified period. If the required translation is not filed in due time, the EPO may disregard the document in question, as for example in T 276/07 (see T 2437/13 for another example). The language to be used for taking evidence and writing the minutes is governed by Art. 14(3) EPC (language of the proceedings) and R. 4 EPC (derogations from the provisions on use of the language of the proceedings in oral proceedings) (Guidelines E‑IV, 1.3 "Taking of evidence" – March 2024 version; chapter III.F.2. "Language of the proceedings"). Compare with T 1787/16, which touches upon the language of the proceedings and the wording of decisions in its detailed reasons while also making a number of references to the language of evidence.

Lastly, see T 2165/18 for a case involving a – highly unusual – request for a transcription of a witness's testimony in the language he had spoken (Polish), the minutes of the hearing being in the language of the proceedings (French). The board refused the request for transcription – and a request for correction of the minutes – as unfounded.

Cross-references: evidential matters permeate all aspects of patent law; it is thus recommended to refer also to the following chapters, which deal specifically with these matters: I.C.2.8.5 "Proof of common general knowledge"; I.C.3.2.3 "Internet disclosures"; I.C.3.2.2 "Lectures and oral disclosure"; I.C.3.5. "Evidence"; I.C.3.5.1 "Burden of proof"; I.C.3.5.2 "Standard of proof"; I.C.3.5.2 c) "Internet – proof of the date of availability"; I.D.4.3. "Solving a technical problem"; II.A.2.2.2 "Burden of proof"; II.C.6.6.7 "Experiments"; II.C.6.8 "Post-published documents"; II.C.9. "Evidence"; II.E.5. "Evidence and standard of proof for allowing amendments and corrections"; III.A.2.3. "Causal link and the requirement of proof"; III.B.2.3. "Surprising grounds or evidence"; III.B.2.4.5 "Failure to consider evidence"; III.B.2.6.4 "Hearing witnesses"; III.B.2.7.1 "Facts and evidence put forward for the first time during oral proceedings in inter partes cases"; III.C.6.3. "Final date for written submissions in the preparation for oral proceedings and late submission of new facts and evidence – Rule 116 EPC"; III.E.4.4. "Substantiation of the request for re-establishment"; IV.B.2.6.5 "Fresh argument based on grounds and evidence communicated beforehand"; IV.C.4.6.2 "No legal basis for disregarding late-filed arguments in opposition proceedings"; V.A.4.4.6 g) "Late-filed evidence of a public prior use – not admitted"; V.A.4.5.11 a) "Late submission of new facts and evidence contrary to the principle of fair proceedings and procedural economy"; V.A.5.5.3 "Late-filed documents and evidence"; V.A.5.13.6 "Public prior use"; III.O.2.6. "Evidence for and effect of a transfer"; IV.C.2.2.8 "Indication of facts, evidence and arguments – substantiation of grounds for opposition"; IV.C.2.2.8 i) "Alleged public prior use"; IV.C.3.4.5 "Examination of fresh facts and evidence related to a fresh ground"; V.A.9.8. "Remittal for hearing of witnesses"; V.B.3.6.4 "Minutes as evidence that the objection was raised". See also Guidelines E‑IV "Taking and conservation of evidence" – March 2024 version.