Members of the competent divisions may not take part in the decision on a case:
For the objection to be admissible it must be raised immediately after the party has become aware of the reason for it. The request must also be accompanied by a reasoned statement of grounds setting out the facts and arguments in support of the objection and, where appropriate, any evidence. Unsubstantiated and merely general statements, e.g. based on the nationality of the examiner(s) concerned, are not admissible.
Any challenge to impartiality must be submitted to the competent division, which will forward it to the responsible superior of the members of the division along with the statement of the member(s) concerned on the facts and circumstances put forward by the party. The responsible superior will decide on the challenge. If the challenge to impartiality has been raised in written proceedings and has been considered allowable, the concerned member(s) of the division is/are replaced. If the challenge has been considered either inadmissible or not allowable, the reasons are issued in writing. These reasons are part of the final decision and will be appealable with it.
If the challenge to impartiality is raised in oral proceedings, the proceedings are interrupted in order for the responsible superior to assess the challenge. On the same day, the oral proceedings are resumed and the parties are informed on the outcome of the assessment. If the challenge is found allowable, the oral proceedings are then adjourned. Proceedings will be continued by a division in which the concerned member(s) is/are replaced.
If the challenge to impartiality is considered either inadmissible or not allowable, the oral proceedings will continue. The parties will be informed of the reasons during oral proceedings. These reasons become part of the final decision and are appealable with it.
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/e_xi.htm
Date retrieved: 17 May 2021