The European Court of Human Rights (ECtHR) delivered three separate judgments today, finding violations for a total of 947 applicants in cases concerning convictions based essentially on alleged use of the ByLock application.
What did Yalçınkaya establish?
In its September 2023 judgment in Yalçınkaya v. Türkiye (Grand Chamber), the ECtHR found that treating ByLock use, on its own, as conclusive evidence automatically establishing all elements — material and mental — of the offence of membership of an armed terrorist organisation raised problems under both Article 7 (no punishment without law) and Article 6 (right to a fair trial) of the Convention. That judgment set out the general principles governing the use of ByLock evidence and became a landmark for subsequent cases.
From Yalçınkaya to today: the line of group judgments
Following Yalçınkaya, the ECtHR began applying the same principles through group judgments covering large numbers of applicants in similar situations. In July 2025, Demirhan and Others became the first group judgment in which the Second Section applied the Yalçınkaya principles collectively, covering 239 applicants. In December 2025, the Seyhan, Karslı and Bozyokuş groups found violations for a total of 2,420 applicants. In June 2026, the Kılıçarslan, Çalı and Dönmez groups covered a further 893 applicants. Today's Parun, Ünal and Korkmaz judgments continue this line, covering a combined 947 applicants.
This succession of group judgments shows that the Yalçınkaya case law is no longer an isolated ruling, but an established line of authority applied systematically to thousands of cases in a similar factual position.
How do today's three judgments apply these principles?
1. Parun and Others v. Türkiye — 345 applicants
The Court found that ByLock use was treated as decisive and automatic evidence in convicting the applicants under Article 314 § 2 of the Turkish Criminal Code. Treating ByLock use as conclusive proof of all elements of the membership offence violated both Article 7 and Article 6 § 1 — the judgment addresses issues of legality and fairness together.
2. Ünal and Others v. Türkiye — 591 applicants
Here the focus is predominantly on the fairness of the proceedings. The Court found it incompatible with the essence of the right to a fair trial that, although ByLock data was the key evidence for conviction, the defence was not given an effective opportunity to challenge that data, technical and legal objections were not adequately addressed, and the courts' reasoning on the ByLock evidence was insufficient. The Court found a violation solely under Article 6 § 1.
3. Korkmaz and Others v. Türkiye — 11 applicants
This judgment focuses on the lawfulness of the conviction. The Court found that treating ByLock use as conclusive evidence automatically establishing all elements of the membership offence violated Article 7.
The difference in focus across these three judgments shows that the ECtHR is now tailoring its reasoning to the factual pattern of each applicant group: Parun addresses legality and fairness together, Ünal focuses primarily on breaches of the defence's procedural rights, and Korkmaz addresses the proof of the offence's elements directly.
Why this matters
From Demirhan onward, eight separate group judgments have now found violations for a combined total of 4,899 applicants (239 + 2,420 + 893 + 947). This development is also relevant for people with similar convictions when assessing retrial requests and domestic remedies.
This article is for general information only and does not constitute legal advice. Every application must be assessed on its own facts and legal circumstances.
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Turkut Legal advises on ECtHR individual applications against ByLock-based convictions and on domestic retrial procedures. To discuss whether your situation falls within this case law, get in touch with us. Counsel available in Turkish, English and German.