EBA hints at accepting "lack of implausibility" standard for inventive step (G2/21)

The Enlarged Board of Appeal (EBA) has issued its preliminary opinion in G2/21 on plausibility. The final decision in this referral has the potential to either lower or increase the plausibility requirement in EPO inventive step analysis. The non-binding preliminary opinion offers a glimpse into what the EBA is thinking prior to oral proceedings. In its preliminary opinion, the EBA hedges its bets but hints at accepting a standard of lack of ab initio implausibility for a technical effect supporting inventive step. 

Case Background: Post-filed data for plausible inventive contribution 

The referral relates to the validity of patent EP2484209 for an insecticide containing two type of compound. The patentee relied on the synergistic effect of the compounds for inventive step. The patent description provides data for the synergistic effect of some example compounds covered by the claims against two species of moth. At Opposition, the Opponent submitted data showing that certain compounds falling under the scope of the granted claims did not have a synergistic effect against another species of moth for which data had not been provided in the patent. 

It's not just cats that are cute

In response, the Patentee submitted post-filed data showing a synergistic effect of some example compounds against yet another species of moth. The question became whether the Opponent's and/or the Patentee's additional data were admissible to debunk or support the inventive contribution of the claimed compounds. 

Referral to the EBA

The full wording of the referred questions is provided below*. A simplified summary of the referring Board of Appeal's questions to the EBA is as follows:

(1) Should post-filed data be disregarded if these data are the sole evidence for a technical effect for inventive step. 

(2) If yes to (1), can post-filed data be taken into account if the technical effect was plausible when the application was filed (ab initio plausibility)

(3) If yes to (1), can post-filed data be taken into account if the technical effect was not implausible when the application was filed (ab initio lack of implausibility)

The practical difference between (2) and (3) rests in where the burden of proof lies. If additional data can only be taken into account when a technical effect is already plausible at the filing date, this puts the burden of proof on the applicant/patentee to show that the effect was plausible at the filing date. If additional data can only be taken into account when a technical effect was not implausible, this lightens the burden for the patentee. It is then up to the patent office or opposing party to provide reasons why an effect would have been implausible to a skilled person at the filing date. 

The difference between plausibility and lack of implausibility was also explored in Warner-Lambert v Actavis [2018] UKSC 56 (IPKat).  

Question 1

Question 1 of the referral in G 2/21 asks whether post-filed data be disregarded if these data are the sole evidence for a technical effect. The preliminary view of the EBA is that the EPO is governed according to the principle of free evaluation of evidence. For the EBA, this principle "does not appear to allow disregarding evidence per se insofar as it is submitted and relied upon by a party [...] and is decisive for the final decision. Disregarding such evidence as a matter of principle would deprive the party submitting and relying on such evidence of a basic legal procedural right generally recognised [...] and enshrined in Articles 113(1) and 117(1) EPC". 

For the EBA, post-filed evidence should therefore not be disregarded. The EBA therefore answers "no" to Question 1. 

Questions 2 and 3

The remaining questions relate to how much weight should be given to post-filed evidence of a technical effect in an inventive step analysis. The EBA is of the preliminary opinion that it is on the basis of the application as filed that the plausiblity of a technical effect should be assessed. Critically, however, the EBA concludes that the test for plausibility is whether a skilled person "would have had any significant reason to doubt" the technical effect at the filing date. In other words, the technical effect must not have been implausible at the filing date. In the lack of any substantiated doubts, the EBA see no reason why post-filed evidence should not be considered relevant to the question:

In the absence of any such doubts, the reliance on post-published evidence, such as experimental data, for the purported technical effect would seems to serve as a potential source for a deciding body to conclude whether or not it is convinced of said technical effect when deciding on the inventiveness of the claimed subject-matter. 

According to the EBA's preliminary view, the plausibility of a technical effect should therefore be assessed according to the same test as the broader principle of sufficiency. The sufficiency of a claim can only be challenged with serious doubts, substantiated by verifiable facts, that the skilled person would have been unable to work the invention. Does this suggest a lowering of the current plausibility bar for inventive step? 

The need to accommodate inventive step arguments against prior art that was unknown at the filing date is one of the reasons for the arguably divergent case law on plausibility. The EBA does not mention in the preliminary opinion whether new evidence can support a technical effect for a post hoc inventive step argument. The EBA merely points out that the technical effect relied upon needs to be encompassed by the technical teaching and "embody the same invention".  

On whether post-filed evidence can be relied on to overcome the fact of an implausible technical effect at the filing date, the EBA does not yet seem to have made up its mind. The EBA merely notes that it "appears questionable" that post-filed evidence could be used to cure ab initio implausibility. 

Final thoughts

In its preliminary opinion, the EBA has accepted that there are questions to be answered but has not yet formed a clear view on those answers. Both parties still have all to play for in the upcoming oral proceedings in Haar on 24 November 2022. Cases in which the outcome of the referral is influential have been stayed until the EBA reaches a decision. 

Further reading

• Enlarged Board of Appeal to tackle the "Humpty Dumpty-ish" plausibility question (G2/21) (25 Oct 2021)
• Reasons for an EBA referral on plausibility, post-published evidence and problem-solution (21 Sep 2021)
• New referral expected to the EBA on the use of post-published data to support inventive step (10 Aug 2021)

*The referred questions

If for acknowledgement of inventive step the patent proprietor relies on a technical effect and has submitted evidence, such as experimental data, to prove such an effect, this evidence not having been public before the filing date of the patent in suit and having been filed after that date (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)?