CASELAW-EPO - reviews of EPO Boards of Appeal decisions

T 1738/21 – Hearing of witnesses necessary

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The patent relates to reinforced bonded abrasive tools, especially to bonded cut-off wheels that can be used to snag or slice materials such as stone or metal.

Brief outline of the procedure

The OD rejected the opposition and the opponent appealed.

In appeal the opponent brought forward questions for a referral to the EBA.

The board decided to refuse the request for referral to the EBA, but considered that the OD had committed a substantial procedural violation (SPV) and remitted the case to the OD for further prosecution.

The case is interesting in view of the reasons for the remittal and for the SPV which resulted from the OD not hearing witnesses about a public prior use.

The board also decided that claim 1 as granted lacked IS over the first document cited on the SESR + common general knowledge.

Claim 1 as granted reads:

A bonded abrasive cut-off wheel (10, 40) comprising …. one or more … reinforcements (50, 54) that are fiberglass webs, wherein the fiberglass webs are coated… characterised by the fiberglass webs having a second coating that excludes wax.

The referral to the EBA

The opponent’s position

The opponent considered that E1=US 3,838,543 was N destroying for claim 1 as granted.

The OD found that there was no disclosure in document E1 that the second coating excluded wax. The opponent was of the opinion that the feature not including wax was a disclosed disclaimer under G 2/10.

For the opponent, an applicant or patent proprietor would have an unfair advantage if claims could be formulated with “absurddisclaimers which would put an undue burden on OD’s and opponents to prove the lack of existence of such an absurd element in the prior art.

The questions for the referral:

1. How are disclosed disclaimers to be taken into account when assessing N and IS, in particular when the N and IS are based on the disclaimer?

2. Do the same requirements regarding N and IS apply to disclosed disclaimers as to positive features?

3. Who has the burden of proof in such cases? Does the EPO or an opponent have to prove that the disclaimer is directly and unambiguously derivable from the prior art? Or must the applicant or patent proprietor prove that the claimed disclaimer is not known from the prior art?

The board’s position

The board confirmed the OD’s decision that claim 1 as granted was novel over E1. 

The board also agreed with the proprietor that feature “excluding waxis not a disclosed disclaimer in the sense of G 2/10 as it does not represent the later disclaiming of something that had originally been claimed but is, and always was, a feature of the claimed invention.  

The board saw no need to refer the questions to the EBA as the assessment of N could be made according to established principles, namely whether the feature is directly and unambiguously disclosed in document E1.

As there is no explicit or implicit disclosure of the exclusion of wax from the second coating in E1, there is no direct and unambiguous disclosure of feature “excluding wax” in the cut-off wheel of E1. Therefore, the opponent had not convincingly shown that the OD was incorrect on this point.

Public prior use

In addition to raising an objection of lack of N of the subject-matter of claim 1 with respect to E1, the opponent also raised an objection of lack of N with respect to an alleged public prior use (PPU). To this effect, the opponent offered witnesses.

The OD found that the alleged PPU did not disclose any specific cut-off wheel with all the features of claim 1.

The opponent’s position

The opponent alleged that a PPU of a cut-off wheel with all the features of the subject-matter of claim 1 of the patent as granted took place on 14,01.2008 through the sale by the opponent itself of 225 cut-off wheels with reference number 61721100 to R. Krueckmeyer GmbH & Co. KG, Dortmunder Str. 4, 57234 Wilnsdorf (DE).

To substantiate its allegations, the opponent filed a delivery note (E18), three written declarations from direct and indirect suppliers of the opponent (E15 to E17), a list of materials (E19), a reinforcement arrangement (E20) and a table showing annual consumption of fibreglass webs (E21).

Five witnesses were offered by the opponent to corroborate the alleged facts.

The opponent thus argued that the OD should have heard the witnesses who had been offered to corroborate its case, before deciding that the alleged PPU did not show a cut-off wheel with the features of claim 1 as granted.

The OD’s position

In the decision under appeal the OD found that the alleged PPU cut-off wheel did not show the subject-matter of claim 1 because:

(a) the PPU cut-off wheel did not disclose a specific cut-off wheel with all the features of claim 1; and

(b) it was not proven that the BAKELITE® coating was still present in the finished cut-off wheel.

In a first summons to OP, the OD gave its preliminary opinion that no specific cut-off wheel was disclosed in the alleged PPU. The OD considered that  

Hearing the witness for proving the PPU of the mentioned materials would be irrelevant for the discussion of N of claims 1 and 13. The witnesses will thus not be invited to the OP”.

In a second summons to OP, the OD confirmed its previous position and stated:

Hearing witnesses for proving the PPU of the mentioned materials would be irrelevant for the discussion of N of claims 1 and 13 which deal with a cut-off wheel and not just with materials suitable for a cut-off wheel. The witnesses will thus not be invited to the OP.”

The OD made no reference to the repeated offer to hear witnesses to corroborate the structure of the cut-off wheel.

The board’s position

In the board’s view, the witnesses who had been offered, were in a position to corroborate the alleged facts which were found not convincing by the OD.

The board noted that it is established case law that an opposition division has violated an opponent’s right to be heard under Art 113(1) if witnesses have been offered in connection with the disclosure of certain features of an alleged PPU considered as adequately substantiated, but the OD decided that the alleged PPU did not constitute novelty-destroying state of the art without hearing the witnesses (CLB, III.B.2.6.4 and III.G.3.1.2).

Therefore, if witnesses have been offered to corroborate alleged facts which are decisive for the decision to be taken, then the OD should hear the witnesses regarding the alleged facts in order to be in a position to take a decision on the basis of all the available evidence (see CLB, III.G.3.1.1 and III.G.4.1).

For the board, it appeared that the witness testimonies, as argued by the opponent, were relevant for the features which were decisive for the decision.

Furthermore, the board could find no mention in the decision under appeal of the opponent’s offer of witnesses nor any indication of the OD’s reasons for not hearing the witnesses who were offered. The board therefore could not review which principles the OD took into account, nor how it applied these principles, when it decided not to hear the witnesses.

In the board’s view, the OD’s failure to hear at least witnesses amounted to a SPV.

Lack of IS

The board decided also that the subject-matter of claim 1 as granted was obvious with respect to the teaching of E1=US 3,838,543 together with common general knowledge. E1=US 3,838,543 was the first X,Y document mentioned on the SESR.


 AS the OD did not consider any AR and as a SPV occurred, the case was remitted to the OD for further prosecution.


A negative statement is not necessarily a disclaimer

In T 154/06 it was held that an originally disclosed feature defined in negative terms is not a disclaimer in the meaning of G 1/03. The present decision has extended this finding to disclosed disclaimers under G 2/10.

Hearing of witnesses

During its hearing, a witness cannot supplement information which should have been filed during the opposition period, cf. T 241/99 or T 2010/08. A witness can neither fill in the gaps in facts brought forward to support the case, cf. T 1100/07.

Hearing or not witnesses is a discretionary decision of the OD. If the discretion has correctly been exercised, be it by hearing witnesses, cf. T 1551/14, or not hearing witnesses, cf. T 41/19 or T 2912/18, a board of appeal will not revise the discretionary decision on the hearing of the witness.

By refusing to hear witnesses, an OD can commit a SPV, cf. the present case or T 273/16.

it should not be forgotten that hearing of witnesses does not necessarily mean the the PPU is confirmed as the witness’ testimony is open to the free evaluation of evidence. See for instance T 660/16 or T 476/14. See also Guidelines E-IV, 5.

On the procedure

When looking at the board’s decision, the patent should never have been granted as the relevant prior art was available in the SESR.

The OD decided to reject the opposition, but the board set aside this decision. The present decision of the OD adds to the long list of decisions set aside by a board upon appeal.

Hearing of witnesses is always involving more work. The OD is also to include a legally qualified member, cf. Guidelines E-IV, 1.3.

Time has to be reserved for hearing the witnesses. In case of a plurality of witnesses, like here, it can drastically extend the time needed for OP.

The temptation for an OD is thus great to avoid hearing of witnesses. This should however not go as far as committing a SPV.

The production/productivity pressure on divisions of first instance is becoming higher and higher, but this should not be to the detriment of the right to be heard of the parties.

However, deciding by the board on the claims as granted on 07.06.2023 with a filing date of 23.12.2009, cannot be taken as an example of “early certainty”.


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