Chapter 1. Proof of Written Disclosure
During the examination, the burden of proof lies with the Examiner (G-IV Guidelines 7.5.3).
If one of the Examiner's arguments is that "it is well known to those skilled in the art", And that the plaintiff disputes it, he will have to prove it with the help of documents (Guidelines G-VII 3.1).
Section 1.1. Proof of an Internet quote
It is incumbent upon the holder to cast sufficient doubt to destroy that presumption, rather than merely invoking a general unreliability of the site.
This level of requirement is much lower than the level of proof a time required by certain decisions: beyond reasonable doubt (T1134 / 06).
Chapter 2. Evidence of Oral Disclosure
The evidence provided must be examined very critical and strict (E-IV 4.3 Guidelines) and the certainty of the Examination / Opposition Division must beyond reasonable doubt (T97 / 94because the evidence relating to a prior public use is all in the possession of the opponent).
2.0.2. Case of conference proceedings
Some consider that the proceedings of the conferences are faithful to the presentations that have been made (G-IV Guidelines 1 and G-IV Guidelines 7.4) until the plaintiff disputes them with legitimate reasons. At the opposition stage, the opponent must prove otherwise.
2.0.3. Case of the speaker's testimony
Proof of oral disclosure can not be provided by having the speaker testify (T1212 / 97 and G-IV Guidelines 7.4), because he is in a very different position from the different parties (eg his disclosure certainly seemed clear to him while his listeners may not have understood anything).
In the same way, it is unlikely that the speaker will remember anything he said several years later (T843 / 15).
2.0.4. Presentation support case (Powerpoint)
One can not simply assume that an oral disclosure matches exactly with its written support (T843 / 15).
If a speaker makes an oral presentation based on a slide show, this document may establish a presumption of the content of the presentation, but this document, in and of itself, is not sufficient to ensure that the content of the slide show has been presented in full and if so, in an intelligible way.
In order to determine what information was actually disclosed to the public during an oral disclosure, it is therefore generally necessary to produce additional evidence, such as statements or written notes from the public, or a handout distributed to the public.
Chapter 3. Evidence of previous use
The level of evidence expected for proof of past use is "beyond reasonable doubt" (T97 / 94).