5.13.1 Legitimate reaction to the first-instance decision
In T 238/92 the board of appeal did not consider a document presented for the first time with the statement of grounds of appeal as "late-filed", since it served as the first evidence of a feature considered in the contested decision as essential for the assessment of inventive step (see also T 117/92).
In the following decisions too, the boards regarded the filing of documents with the grounds of appeal as a legitimate response to the contested decision: T 666/09 (comparative study), T 927/04 (addition to the chain of evidence supporting a prior use), T 815/14 (assertion of a new prior use) and T 113/12 (document a reaction to an amendment of a claim at a late stage in the opposition proceedings).
In T 101/87 the board drew a distinction between (a) the case of an opponent attempting to find further prior art when the opposition division had decided that the original citations did not warrant revoking or restricting the patent, and (b) the case of an opponent making a further search in response to substantial amendments of a claim or to comments from the opposition division regarding a missing link in a chain of argument. In the latter case, new documents could be admitted into the proceedings, instead of being regarded as late-filed.
In T 259/94 the appellants submitted new evidence two years after filing the appeal. The respondent did not object to their introduction into the appeal proceedings. The board held that in such circumstances the principle of "volenti non fit iniuria" empowered it to admit the late-filed evidence.
In T 241/10 the board stated that the board has no power under Art. 12(4) RPBA 2007 to hold a document filed with the statement of grounds of appeal inadmissible if the filing of that document was a legitimate reaction to the submission of amended claims by the patent proprietor shortly before the first-instance oral proceedings and the opponent could not have been reasonably expected to present that document in the proceedings before the opposition division (similar to T 980/09).