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Plausibility and inventive step – two critical hurdles for patenting

Date: 9 November 2021

In the case discussed below, the European Patent Office considers the validity of a patent which is granted on the basis of information which is only published after the patent is filed. Plausibility and information supplied after the filing of a patent application or during an opposition against a patent is critically important in establishing patentability of an invention.


The following sketch schematically illustrates the interplay between inventive step, scope of the claims, disclosure and supplemental data provided after the filing date of a patent application.



In a nutshell, the more the original disclosure of a patent application lacks support of the invention, the lower the plausibility that the invention actually solves the problem asserted. Where not even plausibility is given, the asserted invention may hardly justify the grant of a patent. On the other hand, the more disclosure and plausibility, the more enablement is supported for an invention, and the easier a broader scope of the claims is justified. There may, however, be a negative impact of plausibility and inventive step: the higher the plausibility is for a skilled person, the lower the inventive step may be. Likewise, the higher the inventive step, the higher requirements for plausibility.


In a recent decision, T 0116/18 of October 11, 2021, see EPO - T 0116/18 of 11.10.2021, a Technical Board of Appeal of the European Patent Office (EPO) referred three questions concerning plausibility founded on evidence supplemented to the office after the filing date (also called post-published evidence) to the Enlarged Board of Appeal (EBA). The EBA is an instance at the EPO helping to establish general and uniform standards on the interpretation of the European Patent Convention and for the practice of the Examiners at the EPO, often being implemented in the EPO Guidelines for Examination of patent applications. 


The Board in the referring decision, T0116/18, discussed the fact that the jurisdiction of the Technical Boards of Appeal and the practice of the Examiners showed three different approaches concerning the consideration of post-published evidence. It therefore decided to involve the EBA.


The questions furnished to the EBA are the following:


For the acknowledgement of inventive step a patent proprietor or applicant relies on a technical effect and has submitted evidence, such as experimental data, to prove such an effect. If this evidence was not public before the filing date of the patent in suit (post-published evidence):


  1. Should an exception to the principle of free evaluation of evidence (see e.g. G 3/97, Reasons 5, and G 1/12, Reasons 31) be accepted in that post-published evidence must be disregarded on the ground that the proof of the effect rests exclusively on the post-published evidence?
  2. If the answer is yes (the post-published evidence must be disregarded if the proof of the effect rests exclusively on this evidence), can the post-published evidence be taken into consideration if, based on the information in the patent application in suit or the common general knowledge, the skilled person at the filing date of the patent application in suit would have considered the effect plausible (ab initio plausibility)?
  3. If the answer to the first question is yes (the post-published evidence must be disregarded if the proof of the effect rests exclusively on this evidence), can the post-published evidence be taken into consideration if, based on the information in the patent application in suit or the common general knowledge, the skilled person at the filing date of the patent application in suit would have seen no reason to consider the effect implausible (ab initio implausibility)?


The questions are quite significant. The underlying question is whether the grant of a patent is justified if the information in a patent application does not show that the patentee really was in possession of the claimed invention at the date of filing of the patent.


This alludes to a principle that the extent of monopoly conferred by a patent should correspond to, and be justified by, the actual technical contribution to the art. It is debatable whether a patent is deserved for a patent application which has to rely on later filed supplemental data to obtain the effect claimed. An example would be the filing of a patent application disclosing a protocol for a clinical study without concrete results where the data resulting from the study are provided during patent examination as post-published evidence.


The Case leading to the referral by the Board in T 0116/18 was one where a synergy for a combination of insecticides was only supported by a late filed document (filed in an opposition against a granted patent). The factual case is quite complicated - if interested, please see the link above for details.


The case does not deal with enablement (synergism was no feature of the claims) but with the inventive step of the claimed invention which depended on the plausibility of the (technical effect) synergy based on the late filed evidence as proof.


During the assessment of inventive step, it turned out that questions needed to be referred to the Enlarged Board of Appeal on whether evidence not public before the filing date of the patent in suit and filed after that date ("post-published evidence") can be taken into consideration in view of the plausibility case law of the Boards of Appeal.

The referring Board of Appeal, discussing many decisions from case law, identified three lines of previous case law on the admissibility of post-published evidence:


  1. Ab initio plausibility as standard: In this line of decisions, post-published evidence could be “taken into account only if, given the application as filed and the common general knowledge at the filing date, the skilled person would have had reason to assume the purported technical effect to be achieved” (13.4 of the referral).
  2. Ab initio implausibility as the standard: In this line of case law, post-published evidence “could only be disregarded if the skilled person would have had legitimate reasons to doubt that the purported technical effect would have been achieved on the filing date” of a patent application or patent in suit (13.5 of the referral).

With regard to these two lines of case law, the referring Board (at the end of 13.5.4) concluded that “in this board’s view at least, it is a fundamental question of law whether the ab initio plausibility or ab initio implausibility standard is to be applied”.


The Board then goes on to identify a third line of case law:


3.“No plausibility” standard – this line of case law is described “to reject the concept of plausibility altogether” (13.6 of the referral). This standard is based on the assumption that it cannot be expected from an applicant to include an extensive amount of experimental evidence corresponding to all technical features that could fall under a broad claim. The referring Board, under 13.6.2, cited T 2371/13 which states: “It is usual to invoke a technical effect for inventive step which is not explicitly mentioned in the application as filed. … A lack of plausibility of an effect based on the absence of evidence in the patent application is not a sufficient reason to disregard tests filed later to prove that effect.” This line thus states the lowest necessity of plausibility in the originally filed patent application.


Under 13.7.1 and 13.7.2 the referring Board discusses:


“The three lines of case law discussed above contain two extreme positions, one being a strict application of the ab initio plausibility standard and the other one applying the no plausibility standard. These two extremes illustrate that different results are obtained depending on which plausibility standard is applied. On the one hand, by applying the ab initio plausibility standard strictly, the ultimate result would be that patent applicants receive a patent only for embodiments for which experimental data or other substantiation is contained in the application as filed that makes the effect invoked for inventive step plausible for these embodiments. Hence, any extension of the claimed scope over what has been experimentally shown or otherwise substantiated in the application as filed would lead to refusal of the application. If, on the other hand, no plausibility standard were applied at all, a patent applicant could claim whatever it thinks might possibly be proven later to bring about a purported technical effect. This would give rise to what is often referred to in the case law as "speculative patenting" or "armchair inventions" where a monopoly is conferred to a patent applicant for mere speculation rather than a true invention. The ab initio implausibility standard in terms of its results appears to lie somewhere between these two extreme lines of case law.

… On the other hand, requiring plausibility or at least the absence of implausibility to access post-published evidence can be particularly problematic in cases where an effect needs to be established vis-à-vis a prior-art document that has not been, and perhaps could not have been, considered by the patent proprietor/applicant. … This would mean a basically insurmountable hurdle for patentability once an opponent invokes a new closest prior-art document in opposition proceedings. Furthermore, such an approach would go against decades of case law which has allowed the reformulation of the technical problem in view of new closest prior-art documents and the reliance on post-published evidence in support of the newly formulated problem."


Under 13.7.3, the Board also notices an additional tension between the ab initio plausibility and ab initio implausibility standards on the one hand and the principle of free evaluation of evidence on the other hand: “It is not immediately clear what could be the legal basis for preventing the patent proprietor from relying on a particular type of evidence of a fact relevant to the outcome of the proceedings. Likewise, it is not clear on what basis a board would be prohibited from taking into account evidence it finds convincing and decisive.”


In 13.7.4, the referring Board even expresses doubts whether Inventive Step is a proper legal basis for plausibility.


In summary, it is thus clear that this decision by the Enlarged Board of Appeal might have considerable impact on the drafting and prosecution of patent applications at the European Patent Office and deals with quite fundamental issues to patenting. To what extent the Enlarged Board of Appeal will provide guidance on the issue of plausibility in establishing inventive step, and to what extent it accepts its role and assesses uniform application of the law in that regard, will have to be seen. The issue has an impact on the burden of proof in the case of opposition proceedings: “Under the ab initio plausibility line of case law to which the second referral question refers, it is the patent proprietor that has to prove plausibility while in the ab initio implausibility line of case law, to which the third referral question refers, it is the opponent that has to show implausibility” (14. of the referral).


We can, of course, provide advice on how to establish a solid basis for a patent application by data and theoretical and practical knowledge and can support you by drafting and prosecuting patent applications and defend or enforce patents with a good chance of success, considering and providing advice with regard to the potential issues in view of the plausibility issue, based on experience and an appropriate amount of intuition.


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