a) Both parties have access to the evidence : balance of probabilities 

The standard of the balance of probabilities is applicable when both the patent proprietor and the opponent had access to the material of which public prior use is alleged (see e.g. T 363/96, T 12/00, T 1105/00, T 2043/07, T 1464/05, point 4.3 of the Reasons; T 202/13, point 15.6.2 of the Reasons; T 1170/13, point 2.3 of the Reasons).

In the following cases, it was decided that the evidence did not lie within the sphere of the opponent and therefore that the balance of probabilities was the applicable standard of proof: T 918/11 (selling of containers outside the sphere of the opponent – mass production); T 55/01 (mass-produced goods offered for sale to customers); T 1170/13 (circumstances in relation with prior use showed that opponent did not easily dispose over all the necessary evidence); T 12/00 (in a case involving third parties, both parties could collect evidence); T 1464/05 (no relationship between the opponent and the third party involved in the prior use – sale for test); T 64/13 (prior use based on a purchase agreement between two companies neither of which, according to the respondent (opponent), had a business relationship with it – prior use originally cited by a third company before the German Federal Patent Court).

The balance of probabilities standard is applicable only if the patent proprietor and the opponent had equal access to the material allegedly in public prior use (T 1776/14).

In case T 473/13 the alleged public prior used was by the respondent and patent proprietor, who had initially to prove a confidentiality agreement (burden of proof). The board considered that the much-cited "up to the hilt" criterion did not apply in the present circumstances, since the case law in this respect had been developed for the situation in which a prior use was by the opponent, which was not the case here.

In T 12/00, T 254/98 and T 729/91 the opponent alleging the public prior use was not involved in the circumstances relating to it (T 202/13).