Fair Trials amicus intervention in Silgir v Germany (No 2): Upholding privacy and fair trial rights when encrypted communications data is shared across borders

In March 2026, Fair Trials intervened as an amicus curiae in the European Court of Human Rights (ECtHR) case of Silgir v Germany (No 2). This is one of many recent cases in which encrypted telecommunications data have been accessed by law enforcement in one country, and an evidential product derived from that used at trial in another.

In recent years, this emerging transnational model has attracted particular attention among the Legal Experts Advisory Panel (LEAP), Fair Trials’ network of criminal lawyers, academics and non-governmental organisations from across the European region. Members have raised alarm as to a new dynamic taking hold in European criminal proceedings, in which ‘mutual trust’ (whereby two cooperating states trust each other to act lawfully) has come to justify significant dilutions of core principles of due process.

In 2024, the Court of Justice of the EU (CJEU) considered the EncroChat scenario (which saw French police intercept communications of the entire user base of a system, with other EU Member States obtaining packages of that data under European Investigation Orders). The CJEU held that such operations should not result in a circumvention of states’ local laws on interception of communications, and that evidence derived from EIO cooperation which could not be commented upon effectively should be excluded.

The ECtHR has now also begun to consider this band of cases, including in AL & EJ v France, and Raal & Reudolph v Estonia (pending) as well as the case at hand.

These early cases come at a time when transnational legal cooperation is being enhanced, e.g. through the new UN Convention on Cybercrime (UNCC). Following well-known cases of state abuse of private surveillance tools in recent years (such as Pegasus or Graphite spyware), civil society has expressed significant concern as to misuse of legal interception and evidence-sharing frameworks like the UNCC. This underlines the importance of ensuring that robust rule of law protections apply in such frameworks.

In its intervention, Fair Trials conveyed key practitioner insights from LEAP and certain themes from an anecdotal sample of European judicial practice, including:

• Courts’ reliance on encryption and security features as indicators of criminality when authorising activities directed at the entire user base of a system;
• The lack of transparency in trial states as to the process whereby the data was obtained by law enforcement, processed, and conveyed to the trial state;
• The lack of the underlying ‘raw data’ allowing for the proper verification of the evidential product used downstream in court;
• The significant challenge to defence activity (and to courts’ ability to review the issue) specifically because of the information vacuum created;
• Courts’ reliance on the principle of ‘mutual trust’ in mutual legal assistance environments as a sufficient response to concerns as to evidential integrity;
• Reference to recent decisions of Swiss, Spanish and Italian judicial authorities which suggest a more balanced approach to some of the above issues.

Fair Trials also made limited observations, proportionate to its role as an amicus, on the legal issues before the Court, including:

• Under Article 8 – A state importing data must have a clear and sufficient legal basis for that; inter-state presumptions of trust are subject to the usual human rights limits; and the importing act cannot be lawful if it achieves a circumvention of local law.
• Under Article 6 – Any violations of Article 8 should be vindicated in trial remedies under Article 6; presumptions of mutual trust in the antecedent legal process do not answer concerns as to the technical data handling process thereafter; and there should be access to ‘raw data’ sufficient to enable complete defence activity at trial.

Fair Trials thanks LEAP members for their significant engagement with this exercise via written survey responses and a dedicated consultation call. This produced an unprecedented body of original insight, complementing other research and achieving a new level of dialogue between expert community and international court.

Fair Trials was assisted in the intervention by Counsel Alex Tinsley (UK) and Christophe Marchand, with Marie-Laurence Hébert-Dolbec (Belgium).

The intervention can be downloaded here.