A successful objection of lack of sufficiency of disclosure presupposes that there are serious doubts, substantiated by verifiable facts (see e.g. decision T 19/90, OJ 1990, 476 and decision T 890/02, OJ 2005, 497). In order to establish insufficiency of disclosure in inter partes proceedings, the burden of proof is upon an opponent to establish, on the balance of probabilities, that a skilled person reading the patent, using his common general knowledge, would be unable to carry out the invention (see decision T 182/89, OJ 1991, 391).

A mere statement that one of several examples in a patent has been repeated once "exactly as described" without obtaining exactly the results claimed in the patent is in principle inadequate to discharge that burden (see also T 406/91, T 418/91, T 548/91, T 588/93, T 465/97, T 998/97, T 499/00, T 751/00 and T 967/09). Where the parties make contradictory but unsubstantiated assertions concerning facts relevant for establishing patentability and the EPO is not in a position to establish the facts of its own motion, the benefit of the doubt is given to the patent proprietor (T 72/04). If the patent contains only an example with a hypothetical experimental protocol, and this example is to be relied on for showing sufficiency, then the burden of proof lies on the patentee to show that in practice this protocol works as stated. Evidence that a variation of this protocol works is unlikely to be enough (T 792/00). However, the patent at issue in T 397/02 disclosed a specific humanised version of a mouse antibody and also many specific alternatives thereof. The case was therefore not comparable to T 792/00 (or T 984/00) where not a single specific example of the claimed subject-matter was disclosed. Thus the appellant-opponent bore the burden of proving that the invention could not be carried out.

The board in T 63/06 agreed that the opponent generally bears the burden of proving insufficiency of disclosure. When the patent does not give any information as to how a feature of the invention can be put into practice, only a weak presumption exists that the invention is sufficiently disclosed. In such a case, the opponent can discharge his burden by plausibly arguing that common general knowledge would not enable the skilled person to put this feature into practice. It is then up to the patent proprietor to prove the contrary, i.e. that the skilled person's common general knowledge would enable him to carry out the invention (for a more recent example, see T 338/10, in which the board found that the opponent's reasoned arguments had reversed the burden of proof). In T 491/08 the board, referring to T 63/06 held that a presumption exists that, in general, a patent application relates to an invention which is disclosed in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art. The weight of arguments and evidence required to rebut this presumption depends on its strength. A strong presumption requires more substantial arguments and evidence than a weak one. If a patent application does not contain detailed information of how to put the invention into practice, this requires less substantial arguments and evidence. Serious doubts whether the skilled person can carry out the invention as claimed, e.g. in the form of comprehensible and plausible arguments, are sufficient (see also T 347/15).

In T 518/10, the board looked at the rules concerning the burden of proof of insufficiency, which was, as a general rule, on the opponents. In the case at issue, the appellant (patent proprietor) had asserted that, against the prevailing technical opinion, by using the extraction method described in the patent in suit the skilled person was able to obtain from marine and aquatic animal material an extract comprising compound (II). The respondents denied this and provided evidence that compound (II) could not be obtained when working according to the general method described in the patent. Under these circumstances the burden of proof was on the appellant to show that the method in the patent worked as alleged. The mere assumption that compound (II) could theoretically be present in an extract due to the krill's diet on algae was not evidence that could disprove the respondents' experimental reports or discharge the burden of proof resting on the appellant. The board also did not share the appellant's opinion that it was for the respondents, after having failed to obtain the claimed extract by following the teaching of the patent, to embark on a research programme in an attempt to find a compound which, according to the prevailing technical opinion, was not expected to be found in the first place, and for the presence of which not even the patent in suit provided conclusive evidence.

In T 2571/12 the board disagreed with the conclusions of the opposition division that because no evidence had been provided by the opponent to show that any neuropsychiatric disorder could not effectively be treated using a glutathione precursor the patent in suit was considered as disclosing the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art. It is the patent that has to demonstrate the suitability of the claimed treatment for the claimed therapeutic indication. As explained, for example, in decision T 609/02, a simple verbal statement that compound X may be used to treat disease Y was not enough to ensure sufficiency of disclosure: rather, it is required that the patent provides some information in the form of, for example, experimental tests, to the avail that the claimed compound has a direct effect on a metabolic mechanism specifically involved in the disease, this mechanism being either known from the prior art or demonstrated in the patent per se.

The established case law of the boards of appeal is that a finding of lack of sufficient disclosure should be based on serious doubts, substantiated by verifiable facts. The facts put forward by the examining division in ex parte case T 1020/11 to justify a finding of lack of sufficient disclosure were based on a potential problem which might occur between different antigens in combination. There were however no verifiable facts on file that demonstrated that interference was a problem in the present, specific case. In the absence of such verifiable facts relevant to the specific case, the board could not find the objection of lack of sufficient disclosure persuasive (see also inter partes case T 872/13 concerning a pharmaceutical composition) – the opponent described a number of possible difficulties that the skilled person might encounter, but did not raise any serious doubts substantiated by verifiable facts – in this case the skilled person was in a position to modify the method of Example 8 in order to obtain the desired result – routine modifications).

T 1437/07 dealt with the objection that it was not credible that the therapeutic effect could be achieved because the treatment disclosed in Example 9 had not actually been carried out. The board referred inter alia to R. 42(1)(e) EPC according to which even the presence of an example was not mandatory. The board rejected the objection.

As proof that an invention has been insufficiently disclosed, the boards require that the attempt to repeat it must fail despite following the conditions given in the examples. This requirement is not fulfilled where the opponent repeats the patented process under conditions covered by claim 1 but differing in many respects from those applying in the contested patent's examples (T 665/90). In T 1712/09, the tests referred to in the opponent's experimental reports had been carried out using measuring apparatus different from that described in the patent, and so not as instructed there. The board found that the opponent had made no attempt to reproduce the invention, although this was essential for an objection under Art. 100(b) and 83 EPC and would have enabled it not only to verify or disprove the results but, above all, to calibrate the method of determining the parameter or parameters in question to the values given in the patent. The board therefore held that the opponent had failed to show that the method was unworkable and thus to discharge its burden of proving insufficient disclosure. On the possibility of calibrating methods, see also T 1062/98, T 485/00 and T 45/09.

An invention should be reproduced using the examples given. Insufficiency cannot be proven on the basis of laboratory trials when the only embodiment exemplified in the patent is an industrial fermentation process (T 740/90). The disclosure was also considered sufficient where the opponent had only used equivalents of the surfactants given in the patent, as he had not discharged his burden of proof (T 406/91).

It was held in T 541/96 that if an invention seems to offend against the generally accepted laws of physics and established theories, the disclosure should be detailed enough to prove to a skilled person conversant with mainstream science and technology that the invention is indeed feasible, the onus being on the applicant (see also T 1023/00, T 1329/07 and T 1796/07). The more a new invention contradicts previously accepted technical wisdom, the greater the amount of technical information and explanation is required in the application to enable the invention to be carried out by the average skilled person to whom only that conventional knowledge is available (T 1785/06).

In ex parte case T 2340/12, the application related to a space energy implosion unit. The board observed that it did not understand how the torsion field or space energy was to be measured. The appellant (applicant) claimed that over 40,000 Internet citations could be found concerning "Space Energy". But no specific Internet citation was cited which could serve to explain the concepts of torsion field or space energy. The applicant only referred to "indirect" measurements carried out but did not elaborate on the nature of these experiments or on their relevance for the claimed invention despite having been invited to do so in the provisional opinion issued by the board. The examining division raised criticisms regarding the experiments. The appellant emphasised that the EPC does not contain any requirements for such experimental evidence to be provided. The appellant further questioned the competence of the examining division to require such evidence. The board stated that in the case of inventions in fields of technology without any accepted theoretical or practical basis, the case law of the boards of appeal has established that the application should contain all the details of the invention required for the effect to be achieved (cf. T 541/96, point 6.2 of the Reasons). This was the direct consequence of the fact that the skilled person will be unable to rely on common and accepted general knowledge when dealing with inventions in such fields. The board stated that there is no provision in the EPC according to which the grant of a patent depends on the filing by the applicant of evidence that the claimed invention performs satisfactorily in the form of results of experimentation. The filing of such results is not to be seen as an obligation imposed on the applicant but, in contrast, as a right, providing the applicant with the opportunity to convince the examining division (or the board) that it erred in its initial findings. The decision includes findings on the burden of proof in ex parte cases (see for example, the summary of the rules established by the case law for inter partes cases given in T 967/09, point 6 of the Reasons).

in T 1273/09 the board had serious doubts that the claimed homeopathic treatment of hypertension could be reliably and reproducibly achieved by the mixture claimed for the following reasons, namely (i) because on the standards of "conventional" medicine and science it was inconceivable that a homeopathic medicament which did not contain any active substance achieved specific therapeutic effects and (ii) because on the standards of homeopathic medicine it was inconceivable that a homeopathic medicament that was not applied according to homeopathic principles could achieve specific therapeutic effects. The board could not conclude that the disclosure in the application – and this was the only source of information in the case at issue – put the skilled person in a position to achieve the claimed treatment of hypertension in a reliable and reproducible manner. The reason was not, as suggested by the appellants, a mere, unsubstantiated "disbelief". Rather, the conclusion was drawn by taking into account the quality and quantity of available evidence.

See chapter III.G.5.1.2 c) "Sufficiency of disclosure".