Opening the Door Ajar: T 0644/24 on Amendments and Unraised Opposition Grounds
When a proprietor amends a claim, does it open the entire claim to added matter and sufficiency attacks if those grounds weren't raised in opposition? The Board in T 0644/24 says no, drawing a parallel to G 3/14.
The intersection of procedural strictness and substantive examination is a perennial source of fascination at the EPO. The Technical Board of Appeal decision in T 0644/24 provides a highly instructive look at how the Enlarged Board of Appeal's logic regarding clarity can be transposed to other substantive requirements. It answers a crucial procedural question: if an opponent forgets to raise added matter or sufficiency in the notice of opposition, does a subsequent amendment by the proprietor suddenly open the entire claim to these attacks?
The procedural trap
The case concerned European patent EP 3 811 016, which relates to a device for energy transfer and storage. During the opposition proceedings, the opponent did not raise grounds for opposition under Article 100(b) EPC or Article 100(c) EPC (reasons 1.2). However, during oral proceedings before the opposition division, the proprietor amended the claims to form Auxiliary Request 3.
On appeal, the opponent seized the opportunity to attack the amended claims for both sufficiency of disclosure and added matter (reasons 1.3). Because the proprietor did not consent to the introduction of new grounds for opposition under the framework of G 10/91, the Board had to determine the exact scope of examination permitted for the amended claims (reasons 1.5).
Applying G 3/14 to sufficiency and added matter
The Board drew a direct structural parallel to G 3/14. While G 10/91 establishes that amendments are fully open to scrutiny under the EPC, the Board held that this does not give opponents a free pass to attack features that were already present in the granted patent (reasons 1.5.8).
The Board concluded that if the grounds for opposition under Article 100(b) EPC and Article 100(c) EPC were not raised in the opposition proceedings, an amended patent may only be examined for sufficiency and added matter "to the extent that the amendment introduces the insufficient disclosure or unallowable amendment" (original in German) (reasons 1.5.14).
Because the opponent's primary sufficiency and added matter objections related to features (such as the floor and outer shell) that were already present in the granted claims, the Board dismissed them as inadmissible (reasons 1.6.1–1.6.2).
The missing "nach"
The opponent did manage to squeeze one objection through this narrow procedural door. The proprietor had deleted the word "nach" from the phrase "nach oben" (upwards), restricting the claim to a cover located "oben" (at the top) (reasons 1.8.1). Because this was a direct amendment, the Board admitted the Article 123(2) EPC objection into the proceedings (reasons 1.7.2).
However, the attack failed on the merits. The opponent argued this was an unallowable intermediate generalization because the top cover was only originally disclosed in combination with a specific air inlet gap (reasons 1.9.1). The Board disagreed, noting that the general description of making the cover walkable inherently required it to be the topmost part, independent of the air inlet's design (reasons 1.9.2).
Inventive step and the definition of a framework
The Board also dismissed an inventive step attack over prior art document D2 (a brochure from the Hessischer Staatspreis Energie 2018). The opponent argued that a solid ring wall in D2 constituted a "Ständerwerk" (framework), claiming it was merely a generic term for a load-bearing structure (reasons 2.2.1).
The Board firmly rejected this interpretation. It noted that according to customary technical understanding, a framework consists of discrete supports, which aligned perfectly with the patent's description (reasons 2.2.1). Since D2 lacked this framework and a flexible foil inner shell, and the opponent's reliance on common general knowledge from swimming pool construction was unconvincing for an energy storage device, the subject-matter involved an inventive step (reasons 2.4).
Practical implications
For opponents, the lesson is stark: you must raise all potential grounds for opposition under Article 100 EPC at the outset. Hoping that a proprietor's amendment will accidentally open the door to a full-claim added matter or sufficiency attack is a doomed strategy.
For proprietors, this decision provides welcome procedural security. Amending a claim to overcome a novelty or inventive step objection will not expose the untouched, granted features of that claim to fresh attacks under Article 83 EPC or Article 123(2) EPC. The examination remains strictly confined to the amendment itself.