The assumed infringer of a patent (see D-I, 5) may file notice of intervention in the opposition proceedings within three months of the date on which infringement proceedings were instituted against him or on which he instituted proceedings for a court ruling that he is not infringing the patent. Notice of intervention must be filed in a written reasoned statement. It is not deemed to have been filed until the opposition fee has been paid in the amount prescribed in the Rules relating to Fees under the EPC.
Intervention is permissible as long as opposition or appeal proceedings are pending. A third party can become a party to the proceedings during the period for filing an appeal only if a party to the proceedings in which the decision was given files an appeal pursuant to Art. 107; otherwise the decision of the Opposition Division will become final on expiry of the appeal period (see G 4/91 and G 1/94 ).
A properly filed and admissible intervention is treated as an opposition, which may be based on any ground of opposition under Art. 100 (see G 1/94). This means that, when intervening at any stage of first-instance proceedings, the intervener enjoys essentially the same rights as any other party to the proceedings. If the intervener introduces new facts and evidence which appear to be crucial, the proceedings may need to be prolonged to enable them to be adequately considered. In all other cases the Opposition Division must ensure that the intervention does not delay the proceedings.
If the notice of intervention is filed at a late stage of the proceedings, for example when oral proceedings have already been scheduled, the Opposition Division may dispense with issuing communications under Rule 79(1) to Rule 79(3). The introduction of a new ground for opposition at such a late stage may lead to a postponement of the date set for oral proceedings.
The notice of intervention, filed in a written reasoned statement, must contain: