EPO case law: High standards for transfer of a priority right

The burden of proof for legally valid priority succession lies with the applicant/patent holder. Evidence is subject to the BoA's free evaluation, whereby "beyond reasonable doubt" (and not "balance of probabilities") is to be applied as a standard of proof, because it can be assumed that the evidence is essentially within the control of the applicant/patent holder. Since the EPC does not lay down any formal requirements for the succession of priorities, the question as to whether these formal requirements have been met must in principle be based on the applicable national law. However, this does not release the applicant/patent holder from the obligation to prove that the right of priority has been transferred prior to the filing of the subsequent European application claiming priority (even if the applicable national law would permit retroactive transfers) in order to meet the requirements of Article 87 (1) EPC. The mere demonstration that the priority application was transferred to the applicant/patent holder before the filing of the subsequent European application is not sufficient, even if the applicable national law does not provide for a separate transfer of the priority right from the owner of the first application (EPA BoA 9 February 2017, T 1201/14).