UPC Compass: Prior Art Under Pressure – Striking the Balance Between Efficiency and Fair Trial

Introduction

A recent decision by the Milan Central Division (CD) of 23 October 2025 could create further obstacles for prior art submissions, highlighting the growing focus on procedural efficiency in patent litigation before the Unified Patent Court (UPC). The decision emphasizes the challenge that revocation plaintiffs are facing: including all of the prior art and revocation attacks in the initial revocation action, whilst also being selective as there may be a limit on the number of attacks that the court is willing to consider. Below we examine how this decision, in addition to the existing strict front-loading requirements under the UPC Rules of Procedure, further impacts the balance between efficiency and fairness in UPC revocation actions.

The UPC Rules of Procedure: Front-loading by design

Revocation plaintiffs, whether initiating an action or filing a counterclaim, must present all grounds and supporting evidence at the outset of the proceedings. According to Rule 44 (Statement of revocation) and Rule 25 (Counterclaim for revocation), the following information and documents must, amongst others, be included in the statement or counterclaim:

• an indication of the extent to which revocation of the patent is requested,
• one or more grounds for revocation, which shall be supported by arguments of law wherever possible, and where appropriate an explanation of the claimant’s/defendant’s proposed claim construction,
• an indication of the facts relied on,
• the evidence relied on, where available, and an indication of any further evidence that will be offered in support.

Pursuant to Rule 263, which allows any party, at any stage of the proceedings, to apply to the Court for leave to change its claim or to amend its case, leave shall only be granted if the applicant can satisfy the Court that: (a) the amendment in question could not have been made with reasonable diligence at an earlier stage; and (b) the amendment will not unreasonably hinder the counterparty in the conduct of its action.

Following the cited Rules of Procedure (RoP), all evidence (thus including prior art) should be submitted in the initial court record. Later submissions of evidence are admissible only under strict conditions, unless previously indicated. While this approach aims to minimise tactical delays, it at the same time leaves little flexibility for additional evidence, forcing the revocation plaintiff to submit all potentially relevant prior art at the outset.

By way of contrast, Belgian procedural law, like in many other European jurisdictions, allows also for new evidence and new arguments to be introduced in the trial briefs that are exchanged between the parties after the initial court record. This consequently also applies to proceedings regarding national patents or European patents without unitary effect before the Belgian commercial courts.

The Milan CD’s Decision: Further tightening the reins

The ruling of the Milan CD of 23 October 2025 introduced a new dimension to prior art submissions. Faced with an extensive list of prior art attacks, the Court stated:

“The attacks not identified by [the revocation plaintiff] as (most) promising do not warrant further investigation on the merits because, when the party submits a number of attacks that appear to be unmanageable by the Court in accordance with the principles of proportionality (point 3 of the preamble) and speed (point 7 of the preamble), and the same party is unable to re-module some of the attacks in such a way as to allow the Court to organise its time for the efficient management of the proceedings, it must be considered that if the (most) promising attacks, after assessment of the Court, do not affect the validity of the claim(s), the others wouldn’t have done so either.”

The Milan CD’s filtering is derived from the principles of proportionality and speed of proceedings included in the preamble of the RoP. However, the RoP themselves do not explicitly authorize courts to disregard admissible arguments once filed.

Belgian procedural law, which as mentioned would apply to proceedings regarding national patents or European patents without unitary effect initiated before the Belgian commercial courts, provides for a clear legal framework in this respect. According to the Judicial Code, courts are obliged to address all arguments clearly raised, numbered and ranked in the parties’ trial briefs. Parties may structure arguments in primary and subsidiary order, but courts must acknowledge all arguments, even if secondary ones are not assessed when primary arguments succeed. It is not allowed for courts to decide on the importance of arguments themselves and to not further assess any “less promising” or other arguments of secondary order if the “most-promising” arguments or arguments in primary order are considered unfounded. 

This again stands in stark contrast with the approach adopted by the Milan CD, where secondary prior art attacks may be ignored without explicit mention or justification, even if the attacks qualified as “most-promising” by a UPC division do not affect the validity of the patent.

Fair trial analysis (Article 6 ECHR)

Article 6 of the European Convention of Human Rights (ECHR) guarantees a fair and public hearing, including the right to present arguments and receive reasoned decisions:

• Georgiou v. Greece (14 March 2023): The European Court of Human Rights (ECtHR) found a violation of Article 6 because the national court of last instance failed to address a request for a preliminary reference to the CJEU and gave no reasons.
• Ruiz Torija v. Spain (1994):
  The ECtHR reiterated that Article 6 obliges the courts to give reasons for their judgments, but does not require courts to address every argument in detail. The extent to which this duty to give reasons applies may vary according to the nature of the decision. Further, the Court ruled that the question whether a court has failed to fulfil the obligation to state reasons, deriving from Article 6, can only be determined in the light of the circumstances of the case.
• Hadjianastassiou v. Greece (1992):
  The ECtHR stated that national courts must indicate with sufficient clarity the grounds on which they based their decision.

These cases illustrate the importance of reasoned decisions, which may challenge the Milan CD’s approach if secondary arguments are disregarded without justification.

While the ECtHR does not require courts to answer every single argument of a party, it does emphasise the need for a reasoned decision, taking into account the circumstances of the case. Whether the combination of RoP and the Milan CD’s proportionality stance may invite future challenges under Article 6 ECHR, is therefore to be seen.

Impact

It could be argued that in proceedings regarding national patents or European patents without unitary effect before national courts, parties have, in jurisdictions such as Belgium, more flexibility to refine and build their case throughout the proceedings as well as more transparency regarding the reasoning of the court in its judgment.

UPC revocation actions are less flexible, at least for the revocation plaintiff. Adding the Milan CD’s approach to the mix, this could result in the rather paradoxical situation where that party has to balance between adequately preparing and including as much prior art as possible on the one hand, as additional submissions at a later stage may be refused, while also ensuring to not provide the court with “too many attacks” on the other hand, as this may lead to the court disregarding less-promising arguments.

For patent owners, however, UPC proceedings could evidently be more advantageous, as they allow the patent owner to focus on rebutting selected, clearly structured evidence invoked by the counterparty, with less risk of any unwanted surprises.

Outlook

The UPC’s efficiency-driven model is reshaping European patent litigation, but at the same time shows that the balance between speed and fairness remains delicate. Whether this approach will withstand scrutiny under fundamental rights – and how it compares to national procedural laws – will be a relevant topic for practitioners and scholars alike. Future case law and academic debate will likely shape how the UPC reconciles procedural efficiency with the fundamental right to a fair trial.