Art. 18(2) EPC stipulates that an examining division must consist of three technical qualified examiners. If the examining division considers that the nature of the decision so requires, it shall be enlarged by the addition of a legally qualified examiner.
In T 714/92 the board held that the taking of a decision on a date on which the examining division no longer existed in its stated composition, without the examining division ensuring that it be apparent from the part of the file open to public inspection that the member who left the examining division had agreed the text of the decision before leaving, had to be considered as a substantial procedural violation. Thus the impugned decision was set aside as void ab initio and without legal effect.
In T 160/09 the board found it permissible for the second examiner at oral proceedings to be different from the one who signed the summons. This was not at all comparable to the situation in T 390/86 (see in this chapter III.K.2.2.), where the written decision had not been signed by those members of the opposition division who had delivered the decision during oral proceedings. There is no prohibition on changing the composition of a division, nor is the EPO required to follow a particular procedure to do this.