Evidence of a written disclosure
During the examination, the burden of proof lies with the Examiner (Guidelines G-IV 7.5.3).
If one of the Examiner’s arguments is that « it is well known to the person skilled in the art« , and the applicant disputes it, they will have to prove it using documents (Guidelines G-VII 3.1).
Evidence of an Internet citation
When the citations are Internet pages, the standard level of proof should be used: the balance of probabilities (T286/10, T2339/09 and T990/09 or even T2227/11).
The proprietor has the burden of casting sufficient doubt to destroy this presumption, more than just invoking a general lack of reliability of the site.
This level of requirement is much lower than the level of proof once required by some decisions: beyond any reasonable doubt (T1134/06).
Still, the evidence has to survive the Internet. Where a video (e.g. YouTube) or a web page is cited, its content and the metadata showing when and how it was made available must be collected and preserved so as to remain accessible to the parties, to the public (A128 EPC) and to the Boards. A mere screenshot is not enough: a refusal based on a video that is no longer online is not sufficiently reasoned, hence remittal and reimbursement of the appeal fee (T3000/19, 9 and 10).
Furthermore, the standard of proof for facts must not be confused with the legal test for novelty: whether a document was published on a given date, whether a process leads to a product or whether a known product has a property (e.g. whether a known antibody binds to a polypeptide) are questions of fact, decided on the balance of probabilities; « direct and unambiguous disclosure » only concerns what the skilled person derives from the prior art (T1708/18, 14, 15 and 21).
Evidence of an oral disclosure
Principle
The evidence provided must be examined in a very critical and strict manner (Guidelines E-IV 4.3) and the certainty of the examining/opposition division must go beyond any reasonable doubt (T97/94, as all the means of proof relating to a public prior use are in the possession of the opponent).
Clarifications on the standard of proof
The standard of proof « beyond reasonable doubt » does not require absolute certainty. It is sufficient that the majority of the members of the decision-making body have no reasonable doubt as to the occurrence of an alleged fact (T832/22; see also G2/21).
Case of conference proceedings
Some consider that the conference proceedings are faithful to the presentations that were made (Guidelines G-IV 1 and Guidelines G-IV 7.4) until the applicant contests them with legitimate reasons. At the opposition stage, the opponent must provide proof to the contrary.
However, if the proceedings are published more than 6 months after the conference, the faithfulness of these proceedings can be questioned (T153/88 and T384/94).
Case of the conference speaker’s testimony
Proof of oral disclosure cannot be provided by having the conference speaker testify (T1212/97 and Guidelines G-IV 7.4), as they are in a very different position from the various parties (e.g., their disclosure certainly seemed clear to them while their audience may have understood nothing).
Similarly, it is unlikely that the speaker will remember everything they said several years later (T843/15).
Case of the presentation support (Powerpoint)
One cannot simply assume that an oral disclosure exactly matches its written support (T843/15).
If a speaker gives an oral presentation based on a slide show, this document can establish a presumption of the content of the presentation, but this document, in itself, is not sufficient to guarantee that the content of the slide show was actually presented in full and, if so, in an intelligible manner.
To determine what information was actually disclosed to the public during an oral disclosure, it is therefore generally necessary to provide additional evidence, such as statements or written notes from the public or a handout distributed to the public.
Evidence of prior use
The level of proof expected for the evidence of prior use is « beyond reasonable doubt » (T97/94) when this proof is in the hands of the opponent.
However, if the proof is provided by a witness who is not in the immediate sphere of the opponent (e.g., an independent supplier, T734/18), then the balance of probabilities may apply.
However, this binary approach may prove too formalistic where the evidence lies neither within the opponent's sphere nor in a neutral sphere (e.g. a user manual from a third-party manufacturer having business relations with the opponent): some decisions then hold that neither standard is mandatory and that what counts is the conviction of the deciding body as to whether the alleged fact occurred, in view of the circumstances and the evidence, the two standards remaining reference points in simple cases (T1311/21, 3.2.1 d), following T1138/20, 1.2.1). A proprietor contesting the evidence would also do well to look for counter-evidence itself (e.g. by contacting the purchaser mentioned in the documents).