Two inventors can independently make the same invention. If one of the inventors applies for an intellectual property right (a German patent, a European patent with a German part or a German utility model) before the other inventor files an application or makes the invention available to the public the invention of the other inventor does not impair the protectability. However, the other inventor can invoke a “right based on prior use”, if and inasmuch as he had used the invention in Germany before the filing date or the priority date, respectively, or had started with preparations for such use, and if this use continued later on. Within that scope, the intellectual property right cannot be enforced against him.

One condition for such a right of prior use is the prior user’s possession of the invention. Such possession requires that inventive concept, i. e. the technical teaching involving the combination of the problem and the solution, is subjectively found and the invention is objectively completed (BGH, judgement of 21/06/1960 – I ZR 114/58).

“Subjectively found” does not mean, however, that the prior user would have to explore and unveil all details of the causal chain leading to the inventive success, as the BGH found in its judgement “Desmopressin” (of 12/06/2012 – X ZR 131/09). In the case at hand, the invention related to a pharmaceutical compound having an oxidant level of less than 15 ppm. Complying with this upper limit is essential for the good storage stability of the product. The defendant had previously used inventive compounds with an oxidant level of 3.5 ppm. The lower courts had not ascertained whether the defendant had been aware of the advantages for the stability, because they regarded this fact as irrelevant. The BGH concurred, ruling that the decisive point was that the defendant had found a feasible and reproducible way to produce the compound having 3.5 ppm.

This ruling is convincing because obtaining an intellectual property right likewise does not require a disclosure nor even a deep insight in the causal chain according to which the invention works. So it would be unreasonable to demand additional subjective requirements for establishing a right of prior use. In practice, the main obstacle for the prior user remains: Ensuring the availability of detailed documentation of the development process – usually dating back many years before a legal case.