The basic principle to be adopted is that subject-matter has not been made available to the public by use or in any other way if there is an express or tacit agreement on secrecy which has not been broken.
In order to establish whether there is a tacit agreement, the division must consider the particular circumstances of the case especially whether one or more parties involved in the prior use had an objectively recognisable interest in maintaining secrecy. If only some of the parties had such an interest, it must be established if the other parties implicitly accepted to act accordingly. For example, this is the case when the other parties could be expected to maintain secrecy in accordance with the usual business practice in the relevant industry. For establishing a tacit agreement important aspects to be considered are, inter alia, the commercial relationship between the parties and the exact object of the prior use. The following may be indicators of a tacit secrecy agreement: A parent company – subsidiary relationship, a relationship of good faith and trust, a joint venture, the delivery of test specimens. The following may be indicators of the absence of such an agreement: An ordinary commercial transaction, the sale of parts for serial production.
As a rule, the general standard "balance of probabilities" applies. However, if practically all evidence lies within the power of the party bearing the burden of proof, the facts must be proven beyond reasonable doubt. For example, an opponent alleging that subject-matter was made available without any express or tacit agreement on secrecy must substantiate and, if contested, convincingly prove the circumstances from which public availability can be derived (e.g. ordinary sale to a customer, parts supplied for serial production). The proprietor can challenge this by demonstrating inconsistencies and gaps in the chain of proof or by substantiating facts from which secrecy can be derived (e.g. joint development, samples for test purposes). If these elements lead to reasonable doubts as to public availability, public prior use has not been established.