b) Standard of proof 

In T 2466/13 the board observed that there was no clear line in the boards' case law on the standard of proof to be met: T 205/14 and T 517/14 applied the balance of probabilities, while in T 1201/14, a stricter standard was applied (see above). In T 1786/15, too, the board applied the standard of proof "beyond reasonable doubt". In doing so, it referred to the boards' case law on cases of prior use (in particular T 472/92, OJ 1998, 161) where all the evidence supporting a specific statement of fact was within the power and knowledge of one party (see chapter III.G.4.3.2b). However, according to T 407/15, the balance of probabilities was the standard to be applied. See, however, in this chapter II.D.2.4.3.