Pursuant to Art. 24(1) EPC, members of the boards of appeal or of the Enlarged Board of Appeal may not take part in a case in which they have any personal interest, or if they have previously been involved as representatives of one of the parties, or if they participated in the decision under appeal. Art. 24(3) EPC additionally provides that members of a board of appeal may be objected to by any party for one of the reasons mentioned in Art. 24(1) EPC, or if suspected of partiality.
On that basis, according to the Enlarged Board in G 2/08 of 15 June 2009, Art. 24 EPC foresees two different situations: exclusion and objection. First, under paragraph 1, exclusion ex officio of a member of the boards of appeal for specific reasons, primarily for having a personal interest or having been involved in the decision under appeal. Secondly, under paragraph 3, objection by a party if it suspects a member of a board of partiality. In other words, under "Exclusion and objection" (Ausschließung und Ablehnung; Abstention et récusation) the legislator distinguishes between an irrefutable presumption of law consisting in those compelling grounds of exclusion (judex incapax) that must apply ex officio, and may therefore also be raised by anyone, the parties, the board, or a third person, without their having to justify any personal interest as of right on the one hand, and on the other hand the ground of objection that may be raised by any party to the proceedings if it suspects partiality (judex suspectus) in a member of a board of appeal or of the Enlarged Board of Appeal, since said party enjoys a personal and legitimate interest to act in the proceedings and is entitled to due process of law in respect of said interest. In such a case the burden of proof lies with the party who raises the objection, since members of a Board including the Enlarged Board of Appeal are a priori presumed to be unbiased (G 2/08, point 1.2 of the Reasons).
This distinction is further reflected in Art. 112a(2)(a) EPC (petition for review), which provides that a possible ground of review consists in a member of a board of appeal having participated in a case in breach of Art. 24(1) EPC or despite having been excluded pursuant to a decision under Art. 24(4) EPC. In other words, whereas the grounds under Art. 24(1) EPC are considered to be peremptory due to the violation of the legal principle "ne judex in re sua", the ground which could have justified an objection for suspicion of partiality is not directly foreseen as constituting a priori (i.e. unless proven and decided by the board) a cause of review. Hence, according to the EPC the right to object to a member of a board of appeal or of the Enlarged Board of Appeal is reserved to the party to the proceedings who suspects partiality in such a member (G 2/08, points 1.3 and 1.4 of the Reasons).