Fundamental prior art challenges at the EPO

Can we challenge a cited prior art document on the grounds that it should not have been cited?

Closest prior art at the EPO

The EPO Guidelines state that the closest prior art should be directed to a similar purpose or effect as the claimed invention or at least belong to the same technical field. The recent EPO Board of Appeal decision T 0610/24 exemplifies what this means.

The examining division rejected the application based on document D5. The applicant then argued in appeal that D5 did not address the problem underlying the invention.

T 0610/24

The technical background of the case is relatively straightforward. The application relates to a system for managing the chemical compatibility of pumps and chemicals, essentially addressing the problem of ensuring that pump materials are suitable for particular chemical environments. The cited prior art document D5 also concerned pumps in chemical contexts but did not disclose any information about compatibility-checking. Rather, it addressed pump-related chemical handling on a more general level, without focusing on the specific technical task of evaluating compatibility between a chemical composition and each constituent material of the pump.

The Appeal Board acknowledged that, although there is no absolute obligation to start from a single “correct” closest prior art, starting from a more remote document had in this case led the inventive step analysis down the wrong path by incorporating elements of the solution to the problem statement. Since this undermines the objectivity of the problem–solution approach, the Board sided with the applicant. D5 was in fact not an appropriate starting point for assessing inventive step.

The Board’s reference to additional material (such as D6) illustrated that the technical field of “chemical compatibility of pump materials” exists as a distinct and well-recognised domain. A realistic starting point would then be a document already concerned with compatibility assessments, rather than one dealing more generally with pumps and chemical systems.

The Board did not substitute a different closest prior art and carry out the full inventive step analysis itself. Instead, it recognised that the underlying issue went back to the search and the technical field that had been considered during examination. The Board therefore remitted the case back to the examining division for further examination, noting in section 4.6 that the Board “cannot rule out that a more suitable document addressing the problem of chemical compatibility of pump components exists”.

Section 4.6 also points to the search report as a further indicator that the scope of the search was not comprehensive enough:

“The search report indicates the field of search as “G06Q”. This IPC class relates to information and communication technology (ICT) specially adapted for administrative, commercial, financial, managerial, or supervisory purposes, i.e. systems designed to support the operation and management of an organisation or business. This field does not encompass liquid pumps, let alone issues of chemical compatibility of pumps.”

Conclusions

The EPO’s selection of the closest prior art does not always have to be accepted as an established fact. If the chosen document is not a technically sensible point of departure, the examiner’s objections may be fundamentally flawed.

We may sometimes exploit such flaws without challenging the fundamental validity of a cited document as prior art. A completely unrealistic starting point often facilitates an easy counterargument in favour inventive step. We can happily accept the cited prior art if it gives us a strong argument for inventive step.

But this was not the case in the examination which preceded T0610/24. Here, the prior art was intermediate: not very close and not very distant. D5 showed general similarity to the claimed invention in its terminology and components but lacked the specific focus of the claimed invention. In this specific situation, the applicant was able to successfully argue that D5 did not address the problem underlying the invention and should therefore not have been cited as the closest prior art.

Practical advice:

1. In most cases, it is best to accept the cited prior art as it is and reply with regular counterarguments, even if we may suspect that closer prior art exists.

2. European patent attorneys should know the patent classification system well and pay attention to the field of the search which is listed in every EPO search report.

3. If (a) our regular argument for inventive step seem unpromising for one reason or another, and if (b) the class listed in the search report doesn’t seem to fit the claimed invention, then we may consider objecting against the selected prior art for the (somewhat counterintuitive) reason that more suitable prior art must exist.

4. This strategy should be used as a last resort, and it can probably only be successful under circumstances resembling those of T0610/24.

5. Objecting against prior art for fundamental reasons creates uncertainty. If our objection is successful, we don’t know what prior art examiners might find when they redo their search with a different perspective. In contrast, if we accept the cited prior art as it is, we have a clearer idea of where the examination is headed and what we can try to achieve.

6. Nevertheless, T0610/24 demonstrates that this strategy can in some cases be successful. At the time of writing, the application is in the process of being granted (no new prior art was cited against it).