The Limits of Hindsight: T 0424/23 on Secondary Documents and the Could-Would Approach
The Technical Board of Appeal clarifies that while a secondary document need not explicitly state it solves the objective technical problem, the skilled person still requires a concrete motivation to consult it.
Defending a European patent against an inventive step attack often involves watching an opponent pull a secondary document from a completely different technical context and arguing that the skilled person would simply "recognise" its features solve the objective technical problem. The opponent will insist that the secondary document does not need to explicitly state the solution, provided the mechanics fit. In T 0424/23, the Technical Board of Appeal addressed exactly this scenario, clarifying the boundaries of the problem-solution approach when combining disparate motion mechanisms.
Why did the opponent combine a vehicle simulator with a workshop mechanism?
The patent at issue, EP 3 329 242 B1, claims a land vehicle driving simulator moved by cables rather than traditional linear actuators. The closest prior art, D6, describes a bulky vehicle simulator using linear actuators. The parties agreed the objective technical problem was how to increase the movement area and the amplitude of yawning rotation of D6's mobile platform.
To solve this, the opponent introduced D4, a document describing a small plane motion mechanism used for machining and assembling, which moves a platform using belts. The opponent argued that under the problem-solution approach, the secondary document need not explicitly state it solves the problem, provided the skilled person would recognise D4's belts achieve the desired rotation.
Does a secondary document need to explicitly state the solution?
The Board accepted the legal principle but rejected its application. The panel confirmed that the document to be combined with the closest prior art does not need to state explicitly that it solves the objective technical problem for it to be considered by the skilled person (reasons 17).
However, the skilled person still needs a reason to take such a document into consideration in the first place. The skilled person does not find the secondary document by chance. Applying the could-would approach, the Board noted that D6 focuses on acceleration to simulate real-world driving inertia, whereas D4 focuses on accurate positioning and speed in a workshop application. Without a prompt in D6 to look toward workshop machining mechanisms, the skilled person would only combine these documents with hindsight.
How did the Board handle the sliding means novelty attack?
The opponent also attacked novelty over D1, a vehicle simulation system suspended by nine cables. The opponent argued that the term "sliding means" in the claim was merely a label with no technical limitation, and that the flat base of D1's platform could theoretically contact the floor and slide.
The Board firmly rejected this broad interpretation. Noting that the patent provides concrete examples like pneumostatic blocks and magnetic suspension bearings, the Board held that "sliding means" implies more than an indirect disclosure of a flat surface. Because D1's platform is suspended by cables and its working space excluded the floor entirely, it could not anticipate the claimed sliding means.
Why was the request for remittal refused?
Following the substantive findings, the opponent requested remittal to the opposition division. The opponent argued that its right to be heard required a decision in two instances, as the opposition division had not formally decided on the inventive step attacks starting from D1 or D2 in the impugned decision.
The Board dismissed this request. Relying on Article 111(1) EPC, the panel noted that the opposition division had provided a preliminary opinion on these objections and the parties had submitted extensive written arguments during the appeal. Reaffirming established case law, the Board stated that parties do not have an absolute right to have all issues decided upon by two instances.
What must practitioners prove when combining disparate documents after T 0424/23?
For patent proprietors, this decision provides a robust defence against hindsight combinations. When an opponent attempts to import a feature from a distant technical field, proprietors should focus on the absence of a motivation to consult that field.
For opponents, the lesson is equally clear: identifying a structural match in a secondary document is insufficient. Even if the secondary document inherently solves the objective technical problem, you must first establish a concrete reason why the skilled person, starting from the closest prior art, would open that specific document. Without bridging that motivational gap, the combination will fail the could-would approach.
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Further Reading
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