a) New documents filed in response to experimental data submitted by the patent proprietor – admitted 

In T 23/17 (see also abstract in chapter V.A.4.4.4b)) the board exercised its discretion under Art. 13(1) RPBA 2020 and held plausible and understandable the argument made by the appellant (opponent) that the new documents (filed after the statement of grounds of appeal but before the notification of the summons to oral proceedings) had been filed in response to the experimental data presented by the respondent (patent proprietor) in its reply to the appeal and so, as Art. 13(1) RPBA 2020, put it, "to resolve the issues which were admissibly raised by another party in the appeal proceedings". The board could not see that there had been any reason to file these documents at an earlier stage of the proceedings.

In T 446/16 too, the appellant (opponent) had filed experimental report D35 after its grounds of appeal but before the summons with a view to rebutting the experimental results in D33, which the respondent (patent proprietor) had filed with its reply. The board accepted the reasoning that this response to D33 could not have been filed earlier, finding that the appellant could not be denied an opportunity to cast doubt on the results in D33 in this way.

However, see also T 2688/16 for an example of a case in which a board refused to admit experimental results owing to a lack of adequate reasons for their late filing (see chapter V.A.4.4.4b)).