A petition for review may only be filed on the grounds listed in Art. 112a(2) EPC. Those defined in Art. 112a(2)(a) to (c) EPC concern a breach of Art. 24 EPC governing exclusion of and objection to members of a board of appeal; the participation of persons not appointed as a member of the boards of appeal; and the fundamental violation of Art. 113 EPC. In addition, Art. 112a(2)(d) EPC opens up the possibility of using the Implementing Regulations to define further fundamental procedural defects on which a petition for review might be based (explanatory remarks in OJ SE 4/2007, 126). Under R. 104 EPC, such a defect may arise from either a failure to arrange for the holding of oral proceedings requested by a party (R. 104(a) EPC), or a failure to decide on a request relevant for the board's decision (R. 104(b) EPC). Finally, a petition for review may also be filed on the ground that a criminal act may have had an impact on the decision (Art. 112a(2)(e) EPC).