A person who is being litigated with regard to patent infringement is usually faced with the question on whether or not to attack the patent with a nullity suit. This is because in German litigation proceedings the competent civil court cannot consider the claim that the attacking patent is not valid, because the issues of novelty and inventive step are to be decided by the Federal Patent Court (BPatG) in Munich during the nullity procedure.

Sometimes when a warning letter or an action for infringement is received, one discovers that a third party has already filed a nullity suit against the patent in question.  According to the most recent case law of the German Federal Supreme Court (BGH) it is easier now to join the plaintiff in such proceedings (see Article in German of November 29, 2007).  This reduces the cost risk and is normally also tactically advantageous.

However, the timing of such intervention should be carefully chosen, as has been shown in a case recently decided by the BGH.  Here, the plaintiff had filed an appeal to the BGH after the Federal Patent Court had rejected the suit in the first instance. Only after the term for filing the appeal had expired the intervention of a further party took place.  Subsequently, the defending patent owner made a settlement with the plaintiff in the course of which the appeal was retracted.  The intervening third party requested the continuation of the proceedings, which, however, was dismissed by the BGH (decision of December 16, 2010 – Xa ZR 110/08 – Magnetowiderstandssensor).  A separate appeal of the intervening third party would have been needed for that, which would have had to be filed within the one month term for filing the appeal.

That means that a third party intervention in nullity proceedings should be made either in the first instance or, at the latest, within the term for filing the appeal by means of the own legal remedy. If that is not possible anymore and if an appeal of the plaintiff is pending there is the need for a good coordination with the plaintiff so that the intervention does not lose its basis by means of a one-sided settlement.