a) Burden of proof on appeal 

Concerning burden of proof on appeal, T 1138/20 stated that the burden is on the party challenging a fact on appeal to demonstrate that the first-instance department erred in its finding of fact. In doing so, the party must specifically indicate each alleged error in the department's findings of fact or in its evaluation of the evidence and set out the reasons why this is considered erroneous. If the party succeeds in discharging this burden and demonstrating such an error, the board will establish the facts on its own if this is necessary to reach a decision. Depending on the circumstances of the case, the board may also remit the case to the respective department for a new finding of fact (Art. 111(1) EPC). For the sake of completeness, the board noted the following: since the review of decisions is only one of the functions – albeit the primary function – of the boards of appeal, a board may also decide, at any stage of the appeal proceedings, to establish the facts on its own motion, even if none of the parties has demonstrated an error (see point 1.2.5 of the Reasons).

See also T 1076/21 on the burden of proof on appeal following revocation of the patent by the opposition division. This decision contains an extensive discussion of the burden of proof, the starting point for which is the argument of the respondent (opponent), with reference to T 585/92, that the appellant (proprietor) (now) bore the burden of proving that the patent was sufficiently disclosed because the opposition division had revoked the patent (see point c) below, chapter III.G.5.1.2d)).