In patent nullity proceedings, it may occasionally happen that the plaintiff becomes aware of a relevant prior art document in the course of a renewed search only after the first instance has ended. Pursuant to § 117 German Patent Act in conjunction with § 531 (1) No. 3 German Code of Civil Procedure, an attack based on this new document may be raised in invalidity appeal proceedings if the late assertion of the attack is not due to negligence. In its decision of August 27, 2013 (X ZR 19/12 – “Tretkurbeleinheit”), the German Federal Court has already explained that in such a case the plaintiff must show that the new document could not have been found with a “properly” selected search profile of the search conducted in the first instance. In addition, the plaintiff must explain the details of the first-instance search profile and why he chose such a profile and not the one that led to the discovery of the new document.

The Federal Court has now confirmed this case law in its decision of December 15, 2020 (X ZR 180/18 – “Scheibenbremse”) and has also named a search aspect that should be part of a diligent search. The nullity plaintiff had conducted a first-instance search within the patent class of the patent in suit “F16D 55” and combined the search with the name of individual applicants or with other search terms. Due to these additional search criteria, citation D20, on which the applicant wanted to rely for the first time in the second instance, was not found in the first-instance search.

The Federal Court considered the limitation of the first-instance search by the additional search criteria to be negligent, at least because the search at the same time revealed another document originating from the same applicant as citation D20 and relating to a similar device as the patent in suit. According to the Federal Court, this should have prompted the applicant to extend the search within the patent class of the patent in suit to this applicant. As a consequence, the Federal Court did not admit document D20 into the proceedings.

In view of this, if relevant documents of certain applicants are found by a properly selected search profile, it should be checked whether further relevant documents of the same applicants exist within the patent class of the patent in suit. The additional search not only increases the chances of discovering further relevant documents, but also provides an argument that at least in this regard all due care was observed when conducting the first-instance search.