In T 1140/09 the board stated that, although earlier decisions had applied the standard "beyond reasonable doubt" or "up to the hilt" to alleged public prior use, the standard of proof for the public availability of commercial brochures applied by the boards, even in their recent decisions, was the less strict standard of "balance of probabilities" (see also T 743/89 and T 804/05).
Unlike scientific or technical journals, company papers such as prospectuses or product descriptions cannot automatically be assumed to have made their way to the public (T 77/94; T 37/96). Whether they form part of the state of the art depends instead on the particular circumstances and the available evidence (see also T 1017/01).
In T 77/94, the argument that a publicity notice's date of issue was necessarily immediately after its date of printing (because such notices were only produced in order to be issued) was held to be merely a supposition which required confirmation; in reality, things were often different (see also T 1440/04).
In T 48/96 the board stated that, in order to prove the allegation that a particular apparatus described in a catalogue had been available to the public before the priority date, it was not sufficient to show that the catalogue had been published on time, because a mere indication in a catalogue did not constitute absolute proof that the described product had in fact been available to anybody.
In T 729/91, one relevant document was an issue of a monthly periodical, intended for hoteliers and caterers and which could be bought in South Africa. In accordance with the evidence brought forward in the case, a copy of this periodical was received by a particular library on 9.8.1984, i.e. before the priority date (13.8.1984) of the patent in suit. The librarian stated that publications were "generally available to the public as of the date of receipt". There was no absolute certainty that this was the case with the publication in question. The board was of the opinion that the EPO must decide what had happened having regard to the available evidence on the balance of probabilities, i.e. it must decide what was more likely than not to have happened. In the present case, it was, in the board's view, clearly much more likely that the publication was available to the public as from the date of receipt. In the absence of evidence to the contrary, the board accepted that what had in fact happened was what the librarian stated would "generally" have happened. So the publication was considered to have been made available to the public before the priority date.
In T 55/01 the respondent had argued that only a "complete chain of proof" would suffice to establish that the manual of a television formed part of the prior art. The board agreed that the evidence adduced by the appellant did not form a complete chain of evidence of a sale and noted that, in cases where only one party had access to information about an alleged public prior use, the case law had tended towards expecting that the public prior use be proved beyond any reasonable doubt ("up to the hilt"), answering the typical questions "What?", "When?", "Where?", "How?" and "To whom?", since the other party was reduced to merely pointing out inconsistencies or gaps in the chain of evidence; see T 472/92 (OJ 1998, 161). However, the case law had taken into account the fact that cases of mass-produced consumer goods which were widely advertised and offered for sale to customers who often remained anonymous might require different treatment; see T 241/99. Indeed, to demand a complete chain of evidence in such cases would make it unreasonably complicated for a party to successfully rely on a sale or an offer for sale to prove public availability.
The board observed that televisions were mass-produced consumer products which were rapidly distributed to the market without any obligation of confidentiality. It found that, according to general experience, it seemed highly implausible that such goods, whilst being mass-produced, accumulated at some hidden location. It held that, under these circumstances, no further evidence was necessary to prove that televisions were actually sold to specified customers and that the handbook accompanying them was made available to the public within a period of about four months between their established production date and the priority date of the patent in suit, thereby taking into account the fact that events on the mass market such as the appearance of new television products were readily accessible to everybody, in particular to competitors, who would normally observe the market carefully. Hence, the balance of probabilities was the applicable standard of proof in cases such as this, as distinct from T 472/92.
In T 326/93, the board held that, in assessing public prior use, the burden of proof lay with the opponent, who had to show, on the balance of probabilities, firstly that the invention had been publicly demonstrated before the priority date and secondly that the skilled person would have drawn the necessary teaching from the demonstration (see also T 472/92, OJ 1998, 161; T 750/94, OJ 1998, 32; T 848/94).