The Board of Appeal of the European Patent Office (EPO) has decided that the EPO should in certain circumstances hear witness evidence about an asserted prior use during an opposition. Failure to do so may amount to a procedural violation.


Pfeiffer Vaccum GmbH (Pfeiffer) brought opposition proceedings in respect of Varian S.p.A.'s patent. Pfeiffer argued that there had been a novelty-destroying public prior use. Pfeiffer submitted documents in support of its case and also offered a witness to be heard on this prior use.

The Opposition Division of the European Patent Office (who did not take the opportunity to hear the witness) came to the conclusion that the prior use was not adequately proven and rejected the opposition. Pfeiffer appealed.


The appeal was admissible. Oral evidence need not generally be heard on the subject of whether a prior use was in fact "made available" to the public if:

  • there is no dispute as to the prior use itself; or
  • the use is not novelty-destroying – as in these circumstances, establishing actual disclosure is irrelevant.

In this case, however, the Opposition Division was of the opinion that neither the prior use itself nor whether the prior use was novelty-destroying had been established. The witness offered was able to give evidence on when and how the asserted prior use was made available but also as to what the disclosure was. In these circumstances the witness should have been heard.

The decision was set aside and the case sent back to the Opposition Division


In circumstances where an opponent is seeking to establish lack of novelty by proving that something was "made available" by means of prior use, oral evidence should be offered in support where it is available. It is now clear that there is a requirement to hear such oral evidence in such circumstances. This should be borne in mind, particularly where there is little documentary evidence to support the assertion of a prior use.