In T 190/03 (OJ 2006, 502) (see also T 283/03, T 572/03, T 1193/02, T 1021/01, T 281/03, all published on 18 March 2005) the board observed that there were two distinct aspects of partiality involved in the situations envisaged by Art. 24 EPC 1973. Firstly, partiality for subjective reasons, i.e. an actual partiality on the part of the member, for example due to a personal interest or a dislike of a party. Secondly, a suspicion or appearance that there was partiality, which would be derived by an "objective observer" from a particular action of a member, or an assumed response to a proprietor's action. The board noted that the existence of partiality had to be determined on the basis of the following two tests: Firstly, a "subjective" test requiring proof of actual partiality of the member concerned; secondly, an "objective" test according to which the deciding board judged whether any circumstances of the case gave rise to an objectively justified fear of partiality.
Actual partiality was an internal characteristic of the member himself and its presence was clearly objectionable because it went against the principle of a fair trial. However, suspicion and appearances were not enough to show actual partiality. This was because it was a fundamental duty of a member of a board of appeal acting in a judicial capacity to take decisions objectively and not be swayed by personal interest or other peoples' comments or actions. Indeed, this principle was explicitly contained in the solemn declaration taken by members of the boards of appeal at the time of their inauguration. Thus, personal impartiality of a member of a board of appeal was to be presumed until there was proof to the contrary.
On the other hand, the appearance of partiality involved external aspects and reflected, regardless of whether the member was actually biased or not, the confidence that the board inspired in the public; as the old adage went: "Justice must not only be done; it must be seen to be done" (see also T 900/02, not published in OJ, point 4 of the Reasons, see also T 2291/08). Since this aspect of partiality related to appearances, it did not need to be proved in the same way as actual partiality, but the circumstances had to be assessed to establish whether they gave rise to an objectively justified fear of partiality (objective element). This essentially corresponded to the "objective" and "reasonable" grounds identified above in the case law of the EPO. The board stated that the above was in line with generally acknowledged procedural principles in the contracting states, e.g. the jurisprudence of the European Court of Human Rights (ECHR).