Where a petition for review is allowable, "the Enlarged Board of Appeal may order that members of the Board of Appeal who participated in taking the decision set aside shall be replaced" (R. 108(3) EPC). The Enlarged Board ruling in R 21/11 considered the use of "may" ("peut" in French; "kann" in German) significant because it left it to its discretion whether or not to replace board members. It had to exercise this discretion fairly and proportionately in the light of the facts. If, for instance, it transpired that the members who had participated in taking the decision reviewed were, or might have been, biased, it might be appropriate to order their replacement. But in the absence of any acceptable reason to do so, no such order was to be made, not least to prevent any increase in the costs and duration of proceedings as a result of their reopening. In the case in hand, the Enlarged Board could find no indication of bias and so the board members were not replaced. See also T 584/09.
See also R 15/11, where the Enlarged Board pointed out that the principle relied on in R 21/11, namely that the replacement of members of the board of appeal should not be ordered without good reason, is not merely a matter of procedural economy. The adherence to the Business Distribution Scheme is an important element of an independent, reliable and efficient judicial system which meets the standards set by, inter alia, Art. 6 ECHR. A suspicion of partiality must be justified on an objective basis.