In T 1008/96 the European patent application resulting in the patent in suit and the two Italian utility model applications from which priority was claimed had been filed by different persons. The board held that the succession in title had to be proven to its satisfaction. It was a general principle of procedural law that any party claiming a right had to be able to show that it was entitled to that right (see J 19/87). This question had to be answered in accordance with national law. The board concluded that the respondent had failed to prove that it was the successor in title in respect of the two Italian utility model applications. Consequently, no priority rights existed for the patent in suit.
In T 62/05 the board pointed out that the EPC did not contain any regulations on the formal requirements that an assignment of priority rights for the filing of a European patent application should fulfil in order to be considered valid for Art. 87(1) EPC 1973. However, having regard to the crucial effect that a valid priority date has on patentability (cf. Art. 89 EPC 1973), and to the fact that, in the case at issue, the validity of the priority claim depended on the validity of the transfer of the ownership of the right of claiming priority from the Japanese first filing for the European patent application, such transfer of priority rights, in the board's view, had to be proven in a formal way (cf. T 1056/01). It hence appeared reasonable to the board to apply an equally high standard of proof as that required for the assignment of a European patent application by Art. 72 EPC 1973, which, however, the board concluded was not met here. In particular, the appellant could not convince the board that an assignment had taken place implicitly and tacitly before the end of the twelve month period or that it would have been illogical for the applicant of the priority application to assign the application to the applicant for the patent in suit without assigning the corresponding priority rights.
In T 493/06 it was held that the respondents had provided sufficient proof of the assignment of priority rights. In the board's view even a copy of an assignment agreement could be sufficient provided that evidence was supplied that the content of the copy was identical to that of the original document. Such evidence might, according to board of appeal case law, take the form of an affidavit - even though affidavits were not expressly mentioned in Art. 117(1) EPC 1973 - and the principle of unfettered consideration of the evidence applied to them (see e.g. T 970/93, T 804/94, T 558/95 and T 43/00).
The question of succession in title has also arisen where the validity of the priority claim has been put in doubt in view of a still earlier previous application (see below under point 3. "First application").