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The disclosure must be reproducible without undue burden.
Even though a reasonable amount of trial and error is permissible when it comes to sufficiency of disclosure, e.g. in an unexplored field or where there are many technical difficulties, the skilled person has to have at his disposal, either in the specification or on the basis of common general knowledge, adequate information leading necessarily and directly towards success through the evaluation of initial failures (T 226/85, OJ 1988, 336; following T 14/83, OJ 1984, 105; T 48/85, T 307/86 and T 326/04). Where the skilled person can only establish by trial and error whether or not his particular choice of numerous parameters will provide a satisfactory result, this amounts to an undue burden (T 32/85). Nor can sufficiency of disclosure be acknowledged, if, for an invention which goes against prevailing technical opinion, the patentee fails to give even a single reproducible example (T 792/00).
It suffices for the disclosure of an invention that the means intended to carry out the invention are clearly disclosed in technical terms which render them implementable and that the intended result is achieved at least in some, equally realistic, cases (T 487/91). The occasional failure of a process as claimed does not impair its reproducibility if only a few attempts are required to transform failure into success, provided that these attempts are kept within reasonable bounds and do not require an inventive step (T 931/91). Nor is reproducibility impaired if the selection of the values for various parameters is a matter of routine and/or if further information is supplied by examples in the description (T 107/91). However, wrongly citing a method of measuring an essential product parameter may constitute insufficient disclosure (T 1250/01). According to T 256/87 all that has to be ensured is that the skilled person reading the specification will be able to carry out the invention in all its essential aspects and know when he is working within the forbidden area of the claims. The possibilities of indirect empirical investigation referred to in the specification were, in the board's view, an acceptable solution which sufficed to fulfil the requirements of Art. 83 EPC 1973 without undue burden. This decision was followed in T 387/01, T 252/02, T 611/02 and T 464/05. However, according to several decisions, the concept of 'forbidden area' was rather associated with the scope of the claims, i.e. Art. 84 EPC 1973, than with sufficiency of disclosure (see 6.2 below).
In T 1886/06, the board emphasised that the above finding in T 256/87 could not mean, conversely, that if the claims used a term undefined under Art. 84 EPC 1973 the invention necessarily became impossible to carry out within the meaning of Art. 83 EPC 1973 in the absence, in the description or the common general knowledge of the skilled person, of concrete indications towards a possible definition; doubts as to the claims' reproducibility over their entire scope had to be substantiated by verifiable facts. A mere conjecture that their scope might extend to undisclosed variants was not enough.
There is no requirement in the Convention that the claimed invention may be carried out with the aid of only a few additional non-disclosed steps. The only essential requirement is that each of those additional steps be so apparent to the skilled person that, in the light of his common general knowledge, a detailed description of them is superfluous (T 721/89).
Experiments constitute an undue burden if they have first of all to find the solution to the problem and are not carried out just to determine the numerical limits of a functionally defined range (T 312/88). They should quickly give a reliable picture of how the products can be produced or manufactured (T 475/88). However, it is not necessary for the experimental data filed with the patent in suit to be an exact repetition of the worked examples of the patent, as long as the experimental work can be regarded as being within the scope of the invention (T 674/96).
Where it is obvious that a skilled person would select a particular analytical measuring method, (none being disclosed in the patent), balancing its simplicity and convenience against the required accuracy, the requirements of Art. 83 EPC are met (see e.g. T 492/92). This is the case even if the two different analytical methods proposed by the patentee give significantly different results with the same composition. It also suffices if the person skilled in the art would assume that it was most likely that a certain method was used and this assumption could be tested in the light of the information given in the examples of the patent in suit (T 143/02). However, where there are different measuring methods which do not always lead to the same result, this can amount to an undue burden, as in T 225/93. In T 930/99, the board considered T 225/93 inapplicable, as there was only one measurement method before them. The respondent's argument that there would be legal uncertainty, since third parties would not know whether they were working within or outside the range specified, was clearly an argument based on lack of clarity, which was not a ground of opposition and so could not be considered (see also 6.2 below).
If the description in a patent specification provides no more than a vague indication of a possible medical use for a chemical compound yet to be identified, more detailed evidence cannot be used later to remedy the fundamental insufficiency of disclosure of such subject-matter (T 609/02). Referring to T 609/02, the board in T 433/05 recalled that where a therapeutic application was claimed in the Swiss type form, attaining the claimed therapeutic effect was a functional technical feature of the claim. As a consequence, under Art. 83 EPC 1973 the application had to disclose the suitability of the product to be manufactured for the claimed therapeutic application.
Where the person skilled in the art has to find out by trial and error which, if any, compound meets the parameter set out in the claim, this constitutes an undue burden. The fact that this could be done by routine experimentation was not sufficient for the subject-matter claimed to meet the requirements of Art. 83 EPC. Nor did the question whether or not the parameter could be reliably determined play a role (T 339/05). In T 123/06 the board found that the functional definition of the device was no more than an invitation to perform a research programme, the skilled person only being able to establish through trial and error whether the claimed device was achieved. This amounted to an undue burden.
According to T 815/07, the purpose of a parameter contained in a claim is to define an essential technical feature of the invention. Its significance is that the presence of this technical feature contributes to the solution of the technical problem underlying the invention. The method specified for determining the parameter should therefore be such as to produce consistent values, so that the skilled person will know when he carries out the invention whether what he produces will solve the problem or not.
According to T 1063/06 (OJ 2009, 516), a functional definition of a chemical compound (in this case in a reach-through claim) covered all compounds possessing the capability according to the claim. In the absence of any selection rule in the application in suit, the skilled person, without the possibility of having recourse to his common general knowledge, had to resort to trial-and-error experimentation on arbitrarily selected chemical compounds to establish whether they possessed the capability according to the claim; this represented for the skilled person an invitation to perform a research programme and thus an undue effort (following T 435/91). See also T 1140/06.
According to T 954/05, the structural definition of a chemical compound may not be replaced in a claim by the mere juxtaposition of a feature purportedly representing a complete chemical structure and of a functional feature if:
- on the one hand the first feature comprises an indefinite number of compounds and there is no systematic selection rule based on the feature in question enabling the skilled person to identify the claimed compounds, and
- on the other hand the second, functional feature is not identifiable in the indefinite list of compounds potentially suitable for such a function because there is no indication of a typical standardised test for determining its presence or absence.