3.4.1 Fresh grounds examined exceptionally

In G 10/91 (OJ 1993, 420) the Enlarged Board held that in principle, the opposition division shall examine only such grounds for opposition, which have been properly submitted and substantiated in accordance with Art. 99(1) EPC 1973 in conjunction with R. 55(c) EPC 1973. Exceptionally, the opposition division may in application of Art. 114(1) EPC consider other grounds for opposition, which, prima facie, in whole or in part would seem to prejudice the maintenance of the European patent (see also the summary of G 10/91 in this chapter IV.C.3.3. above).

This exercise of discretion by the opposition division is reviewed by the boards in accordance with the principles set out in G 7/93, according to which boards of appeal should only overturn discretionary decisions of first instance if it is concluded that the first instance exercised its discretion according to the wrong principles, or without taking into account the right principles or in an unreasonable way (see e.g. T 1005/14, T 1965/17, T 3077/19). For an example where the board found the opposition division had exercised its discretion to admit a new ground for opposition unreasonably, see T 375/21.

See also chapter V.A.3.4 "Review of first-instance discretionary decisions"