Background
Following the attempted military coup in Turkey on 15 July 2016, Turkish authorities prosecuted thousands of individuals for membership of the “Fetullahist Terror Organisation/Parallel State Structure” (FETÖ/PDY), which the government held responsible for the coup attempt. The 595 applicants in this consolidated case were among those convicted under Article 314 § 2 of the Turkish Criminal Code for membership of an armed terrorist organisation. Their convictions rested decisively on evidence that they had used “ByLock,” an encrypted messaging application that Turkish authorities characterised as having been designed exclusively for FETÖ/PDY members.
Turkish courts took the position that establishing a person’s use of ByLock was, on its own, sufficient proof of all constituent elements of the offence of membership of an armed terrorist organisation. In some cases convictions were entered before the detailed ByLock analysis and decrypted message reports had even been submitted to the case file, on the ground that mere use of the application was conclusive. Additional evidence against some applicants included membership of FETÖ/PDY-affiliated unions or foundations, accounts at Bank Asya, pro-FETÖ/PDY publications, residence in affiliated student housing, and social media activity, but the ByLock finding remained the decisive basis for conviction in each case.
Each applicant challenged their conviction before Turkey’s Constitutional Court by way of an individual application. Those challenges were summarily dismissed as inadmissible by the Constitutional Court, which endorsed the Court of Cassation’s landmark judgments approving the ByLock-based conviction framework. The applicants then brought proceedings before the European Court of Human Rights, relying principally on the Grand Chamber’s earlier judgment in Yüksel Yalçınkaya v. Türkiye (no. 15669/20, 26 September 2023) and the Chamber judgment in Demirhan and Others v. Türkiye (nos. 1595/20 and others, 22 July 2025).
The Court’s Holding
The Second Section Committee, sitting unanimously, found violations of both Article 7 (no punishment without law) and Article 6 § 1 (right to a fair trial) of the Convention. Applying the principles established in Yüksel Yalçınkaya and reiterated in Demirhan and Others, the Court held that the domestic courts’ approach of treating ByLock use as conclusive proof of armed terrorist organisation membership effectively imputed objective criminal liability to ByLock users, in contravention of the principle of legality under Article 7. The Court rejected Turkey’s argument that the cases should each be assessed in isolation on their individual facts, reaffirming that the structural problem identified in Yüksel Yalçınkaya was not confined to that case but applied to all persons convicted of FETÖ/PDY membership on the basis of ByLock use.
On the Article 6 § 1 fair trial complaint, the Court found that, regardless of procedural differences between individual cases, the domestic courts’ uniform and global treatment of ByLock evidence defined the procedural framework in all the proceedings at issue. The courts failed to put in place appropriate safeguards to allow applicants to effectively challenge the ByLock data, failed to address the core evidentiary issues, and failed to give adequate reasons for their decisions — falling short of the minimum requirements of Article 6 § 1. The Court also declined to hold that any derogation under Article 15 of the Convention was justified: while acknowledging Turkey’s exceptional difficulties in the aftermath of the coup attempt, it found no basis to conclude that the limitations on fair trial rights were strictly required by the exigencies of the situation.
The Court declined to examine the applicants’ remaining complaints under Articles 5, 8, 9, 10, 11, and 14 of the Convention, having addressed the principal legal questions through the Article 7 and Article 6 § 1 findings. On just satisfaction, the Court held that the finding of violations itself constituted sufficient just satisfaction for non-pecuniary damage, noting that Article 311 § 1(f) of the Turkish Code of Criminal Procedure permits reopening of domestic proceedings following a Strasbourg judgment — which would represent the most appropriate form of individual redress. No award was made for costs and expenses.
Key Takeaways
- Convicting a person of armed terrorist organisation membership solely on the basis of ByLock app use — without requiring proof of the individual’s actual organisational role, activities, or submission to the group’s hierarchy — violates the Article 7 principle of no punishment without law by imputing objective criminal liability.
- The procedural shortcomings identified in Yüksel Yalçınkaya are structural in nature: they attach to any conviction grounded in the domestic courts’ uniform ByLock framework, not merely to the specific facts of that lead case, and cannot be cured simply by pointing to additional evidence in individual files.
- Turkey’s post-coup security emergency does not satisfy the Article 15 threshold for derogating from the fair trial guarantees at issue; the limitations imposed on the applicants’ procedural rights were not strictly required by the exigencies of the situation.
- The finding of a violation is itself sufficient just satisfaction; the most appropriate remedy is reopening of domestic proceedings under Turkish procedural law, should applicants request it.
Why It Matters
This judgment consolidates 595 individual applications and signals that the Strasbourg Court intends to resolve the large backlog of post-2016 Turkish terrorism cases through systematic application of the Yüksel Yalçınkaya framework rather than case-by-case fact review. Turkey faces a significant structural compliance challenge: tens of thousands of individuals were convicted using the same ByLock-based approach, and the judgment expressly contemplates mass reopening of domestic proceedings as the primary vehicle for redress.
For practitioners advising clients with pending or concluded FETÖ/PDY prosecutions, the ruling confirms that neither additional corroborating evidence nor the scale of the national security threat is sufficient to immunise ByLock-based convictions from Convention scrutiny. The Court’s refusal to entertain Turkey’s case-by-case differentiation argument forecloses a key government strategy for limiting the reach of Yüksel Yalçınkaya, and places sustained pressure on Turkey to reform its approach to digital evidence in terrorist organisation prosecutions.