4.3.2 Public prior use

Although the standard of proof is the same for all objections covered by Art. 100 EPC (cf. T 270/90, OJ 1993, 725), the case law identifies two levels or standards of proof to be applied with regard to disputes around public prior use – either the "balance of probabilities" or "up to the hilt". The board in T 1138/20 provides qualification in this regard.

Decision T 1311/21 endorsed T 1138/20 and stated that the binary approach to proof standards could turn out to be overly formalistic and simplistic. What mattered was the deciding body's conviction on the occurrence of an alleged fact, taking into account the particular circumstances of the case and the relevant evidence before it. In the case in hand, the board was of the opinion that neither standard of proof was applicable. See also T 832/22.

In T 778/21, the board considered the standard of proof "beyond all reasonable doubt", stating that the applicable standard of proof was either “beyond all reasonable doubt” (T 97/94) or that the deciding body had to be convinced with a sufficient degree of certainty (T 1138/20, T 545/08).

About burden of proof, see decision T 2037/18, which sets out detailed reasons on the issue (prior use; distinction between the admissibility and the substantive merits of the opposition; burden of presentation and burden of proof; principle of "negativa non sunt probanda" (aspect also mentioned in R 1/20); non-confidentiality clause; shifting of the burden of proof) and cites numerous other decisions.

For the distinction between evidence of prior use and evidence of oral disclosures, see T 1023/20 (point 1.1.3 of the Reasons), also dealt with under present chapter III.G.4.3.3.