Applying G 1/24 to Added Matter: T 0873/24 Refers Claim Interpretation

The mechanics of claim interpretation have dominated European patent practice since the Enlarged Board of Appeal issued G 1/24. While that landmark decision explicitly addressed patentability under Articles 52 to 57 EPC, its downstream effect on the assessment of added matter under Article 123(2) EPC has fractured the case law of the Boards of Appeal into three distinct approaches. In T 0873/24, Board 3.3.05 has referred this exact tension to the Enlarged Board, pairing it with a fundamental challenge to the admissibility threshold for referrals itself.

How did a missing unit trigger a referral?

The technical dispute in this case turned on a single missing word. Claim 1 of the patent in suit, directed to coated steel strips, requires that "the ratio of titanium to nitrogen is in excess of 3.42". However, the original application explicitly defined this as a weight ratio. The opponent argued that omitting the unit generalised the feature to encompass a molar ratio, thereby adding subject-matter. The patent proprietor countered that a weight ratio was implicit from the preceding claim features and standard metallurgical drafting practice.

The Board rejected the proprietor's arguments, noting that a molar ratio makes technical sense and that the word "wherein" does not link the units of separate features. The case therefore hinged entirely on whether the description, which exclusively disclosed a weight ratio, could be used to restrict the open claim wording.

How does G 1/24 apply to Article 123(2) EPC?

The Board noted that most recent decisions acknowledge that the principles of G 1/24 apply to added matter assessments, typically employing a two-step approach: first interpreting the claim, then assessing the interpreted subject-matter against the gold standard. However, the Board identified three divergent approaches to that crucial first step:

1. Consulting the description only to identify the technical field and the skilled person, leaving the claim open to all technically sensible interpretations.
2. Refusing to read features or restrictions from the description into the claim, precluding a purposely restricted interpretation.
3. Adopting a holistic approach where claim interpretation is a unitary process of reading the claims and consulting the description, permitting the narrowing of an open term if derived from the patent as a whole.

Why did the choice of interpretive approach dictate the outcome?

The Board demonstrated that the fate of the patent depended entirely on which approach was applied. Under the first and second approaches, the open ratio encompasses a molar ratio. Because a molar ratio of more than 3.42 implies adding titanium in at least a 3.42-fold molar excess (reasons 3.2), this interpretation makes technical sense but lacks basis in the application as filed, leading to a violation of Article 123(2) EPC.

Conversely, under the third approach, the Board observed that the description exclusively discusses a weight ratio to achieve a stoichiometric amount for scavenging nitrogen. Applying this holistic view, the open ratio is interpreted restrictively as a weight ratio, perfectly aligning with the original disclosure and saving the claim. This stark divergence prompted the substantive referral questions.

When is a referral procedurally "required"?

Before reaching the substantive questions, the Board had to tackle admissibility. Article 112(1) EPC states a referral must be "required". Recent case law, notably T 116/18, interpreted this strictly, holding a referral inadmissible if the patent might ultimately be revoked on other grounds (such as Article 56 EPC) regardless of the Enlarged Board's answer.

Board 3.3.05 strongly disagreed. Pointing to the 107 auxiliary requests on file, the panel argued that forcing a board to examine every other objection before addressing the most straightforward one leads to an impractical and inefficient manner of structuring proceedings (reasons 4.4.2). Relying on a broader reading of G 3/98, the Board formulated a preliminary referral question asking whether a decision is "required" simply if it is reasonable for the Board to examine it and decide on it next.

What must practitioners prepare for while this referral is pending?

Until the Enlarged Board answers these referred questions, the boundary between permissible claim interpretation and impermissible added matter remains volatile. Patent proprietors cannot safely assume that a holistic reading of the description will save a claim feature that has been generalised by the omission of a unit.

When drafting or amending, practitioners must ensure that critical parameters, such as the basis for a ratio, are explicitly defined in the claims themselves. Furthermore, opponents should actively identify instances where a proprietor relies on the description to restrict an otherwise broad, technically sensible claim interpretation, as the Enlarged Board may ultimately endorse the stricter approaches that forbid reading such limitations into the claims.

Sources

• T 0873/24, Full decision
• G 1/24
• Article 123(2) EPC
• Article 112(1) EPC
• T 116/18
• Article 56 EPC