9.2. Consequences of a strong or weak presumption for sufficiency of disclosure

The board in T 63/06 (see "headnote") 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 shifted the burden of proof, and, to the same effect, T 518/10; compare also with T 792/00, point 9 ff of the Reasons (burden of proof in case of a hypothetical experimental protocol)).

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; T 1845/17 (ambiguous parameter); T 2218/16 (Gene therapy of motor neuron disorders – scAAV9 vector), which summarises the case law on the burden of proving an alleged lack of sufficient disclosure).

The board in T 59/18 stated, in relation to the burden of proof when a weak presumption exists that the invention is sufficiently disclosed (reference made to T 63/06), that since the respondents (opponents) had convincingly argued that the term "relaxation ratio" having the meaning intended by the appellant was not to be found in textbooks and did not represent common general knowledge, the burden of proof for establishing sufficiency was clearly on the appellant/patent proprietor.

In T 2119/14 (unusual parameter) the board, referring to T 63/06 (concepts of strong presumption and weak presumption in relation to the burden of proof), held that the existence of an undue burden resulted from the almost infinite number of coating compositions that fell under the structural definition given in claim 1, and the established absence of a teaching in the patent in suit as to how select in an appropriate and straightforward manner the components of the coating composition so as to meet the unusual parametric requirement of claim 1. As a consequence, the onus of proving that the preparation of the coating compositions over the whole scope for which protection was sought did not necessitate an undue amount of work for the skilled person rested with the patent proprietor (here: appellant).