The Boundaries of Reformatio in Peius: T 1142/24 Applies G 1/99 to Substituted Features
In T 1142/24, the Board of Appeal applied G 1/99 to reject an auxiliary request that replaced a daily milk yield limitation with a variable reference period, violating the prohibition of reformatio in peius.
A patent proprietor defending an interlocutory decision against an opponent's sole appeal cannot replace a specific temporal limitation with a broader feature, as this violates the prohibition of reformatio in peius established in G 1/99.
Why did the Board find the individual target yield feature obvious?
The patent, EP 3 678 474, concerns a method for milking cows where the milking process stops automatically once a target milk yield, which is lower than the expected yield, is reached. The Main Request required the target milk yield to be determined "for each individual milking operation". The opponent argued this lacked an inventive step over D2, which disclosed calculating a threshold value from historical data for the first milking turns of a lactation period.
The proprietor countered that D2 only calculated a single target yield applied repeatedly, rather than determining a specific yield for each consecutive milking. The Board in T 1142/24 rejected this distinction. They held that the claim wording encompassed both calculating a new target each time and pre-calculating a single target that is then applied to each individual milking operation (reasons 1.3.1). The Board noted that assessing an inventive step presupposes novelty. Because D2 disclosed this pre-calculated target, there were no distinguishing features, meaning the claim could not involve an inventive step (reasons 1.3.4).
How did the deletion of the daily reference period trigger G 1/99?
With the Main Request falling, the proprietor turned to Auxiliary Request III. Because the opponent was the sole appellant against the opposition division's interlocutory decision, the proceedings were governed by the prohibition of reformatio in peius under G 9/92 and G 4/93. The proprietor was primarily restricted to defending the claims as maintained.
Auxiliary Request III deleted the requirement that the target yield be determined "for each day" and instead required that the yield be changed from a reference yield by a change value M. The proprietor argued this was a mere restriction that implicitly retained the daily limitation. The Board disagreed. By removing the "for each day" requirement, the claim no longer limited the reference period to a 24-hour cycle (reasons 2.3). A target yield could now be defined over 48 hours or a fraction of a day, encompassing subject-matter not covered by the Main Request.
Why did the Board refuse to admit the amended auxiliary request?
Admitting a request that broadens a temporal limitation would put the sole appellant in a worse position than if they had not appealed at all. The Board noted that the amendment introduced a multitude of additional target milk yield definitions that were absent from the Main Request (reasons 2.4). Furthermore, the amendment removed the definition of how the target yield was determined on the first day, creating another unallowable extension (reasons 2.5).
Since none of the exceptions outlined in G 1/99 applied, and the proprietor did not argue that they did, the Board refused to admit Auxiliary Request III into the proceedings (reasons 2.6). Consequently, the patent was revoked.
Which exceptions does G 1/99 allow, and in what order?
The exceptions the Board found inapplicable follow a strict scheme. According to G 1/99 (headnote), an exception to the prohibition may be made in order to meet an objection raised by the opponent/appellant or by the Board during the appeal proceedings, if the patent as maintained in amended form would otherwise have to be revoked as a direct consequence of an inadmissible amendment that the opposition division had held allowable in its interlocutory decision.
In such circumstances, the proprietor/respondent may be allowed to file requests in the following order (G 1/99, headnote; recited in T 1168/24, reasons 29):
- In the first place, an amendment introducing one or more originally disclosed features which limit the scope of the patent as maintained.
- If such a limitation is not possible, an amendment introducing one or more originally disclosed features which extend the scope of the patent as maintained, but within the limits of Article 123(3) EPC.
- Finally, if such amendments are not possible, deletion of the inadmissible amendment, but within the limits of Article 123(3) EPC, even if the situation of the opponent is thereby made worse.
The order is mandatory: a later remedy is only available where the earlier one is impossible (T 1168/24, reasons 29 and 30, citing T 724/99). Two consequences follow for cases like T 1142/24. First, the ladder is opened by a deficiency that would otherwise force revocation of the maintained version, not by the proprietor's wish to reposition the claims. Second, the proprietor must actually invoke and substantiate an exception: in T 1142/24, the Board noted that none of the exceptions applied and that the proprietor had not argued otherwise (reasons 2.6).
What must patent proprietors consider when amending claims under a sole opponent appeal?
When defending a patent against an opponent's sole appeal, proprietors must ensure that any fallback requests do not inadvertently broaden any aspect of the claims maintained by the opposition division. Replacing a specific operational limitation, such as a 24-hour reference period, with a mathematically different limitation, such as a variable reference yield, carries a high risk of violating the prohibition of reformatio in peius.
Practitioners must meticulously verify that every limitation from the maintained claims is either explicitly retained or genuinely narrowed in the auxiliary requests. Relying on the argument that a new feature implicitly contains the old limitation will fail if the new wording theoretically permits broader operational parameters.