SECOND SECTION
CASE OF DÖNMEZ AND OTHERS v. TÜRKİYE
(Applications nos. 24039/21 and 33 others –
see appended list)
JUDGMENT
STRASBOURG
23 June 2026
This judgment is final but it may be subject to editorial revision.
In the case of Dönmez and Others v. Türkiye,
The European Court of Human Rights (Second Section), sitting as a Committee composed of:
Jovan Ilievski, President,
Péter Paczolay,
Juha Lavapuro, judges,
and Dorothee von Arnim, Deputy Section Registrar,
Having regard to:
the applications against the Republic of Türkiye lodged with the Court under Article 34 of the Convention for the Protection of Human Rights and Fundamental Freedoms (“the Convention”) by the applicants listed in the appended table (“the applicants”), on the various dates indicated therein;
the decision to give notice of the complaints under Article 6 § 1 (the right to a fair trial) and Article 7 of the Convention (no punishment without law) to the Turkish Government (“the Government”) represented by their Agent, Mr Abdullah Aydın, Head of the Department of Human Rights of the Ministry of Justice of the Republic of Türkiye;
the parties’ observations;
the decision to reject the Government’s objection to the examination of the applications by a Committee;
Having deliberated in private on 2 June 2026,
Delivers the following judgment, which was adopted on that date:
SUBJECT MATTER OF THE CASE
1. The case concerns the applicants’ convictions for membership of an armed terrorist organisation described by the Turkish authorities as the “Fetullahist Terror Organisation/Parallel State Structure” (Fetullahçı Terör Örgütü / Paralel Devlet Yapılanması, hereinafter referred to as “the FETÖ/PDY”), considered by the authorities to be behind the coup attempt that took place in Türkiye on 15 July 2016. The broader domestic background and context to the present applications was set out by the Court in Yüksel Yalçınkaya v. Türkiye ([GC], no. 15669/20, §§ 10-22 and 108-40, 26 September 2023).
2. The applicants’ convictions were based decisively on their use of an encrypted messaging application by the name of “ByLock”. The domestic authorities and courts considered that the ByLock application was designed for the exclusive use of the members of the FETÖ/PDY and that the establishment of the use of that application was sufficient on its own for conviction under Article 314 § 2 of the Criminal Code for membership of an armed terrorist organisation (ibid., §§ 155-65 and 257).
3. Other evidence against the applicants, if any, involved mainly an admission of using ByLock, decrypted message content confirming use of that application or witness statements attesting to such use; membership of a trade union, association and/or foundation considered to be affiliated with the FETÖ/PDY; account activities at Bank Asya, which was considered by the authorities to be a part of the financial structure of the FETÖ/PDY; possession of pro-FETÖ/PDY publications or other audio-visual material; participation in trips considered to have been organised by the FETÖ/PDY and records of exit from and entry to Türkiye; donations to FETÖ/PDY-affiliated foundations; participation in various demonstrations considered to be in support of the FETÖ/PDY or in other organisational activities; social media posts in favour of the organisation; residence in FETÖ/PDY student houses or dormitories; use of other messaging applications, such as Kakao Talk or Eagle, to communicate with other members of the organisation; HTS (Historical Traffic Search) records indicating communications with others prosecuted for the same offence or other digital evidence suggesting membership of the organisation; employment by and/or membership of FETÖ/PDY‑affiliated institutions, organisations or companies; witness statements as regards such employment and/or membership, or as regards other connections to the FETÖ/PDY. In the case of some of the applicants, the convictions were imposed without waiting for the submission to the case files of the detailed ByLock findings and evaluation reports – which potentially included decrypted content of communications over ByLock – on the ground that the establishment of the use of that application sufficed for conviction, irrespective of the nature and content of the communications.
4. The individual applications lodged by the applicants with the Constitutional Court against their convictions were summarily dismissed by that court as being inadmissible, on the basis of its case-law endorsing the Court of Cassation’s landmark judgments on the matter (see Yüksel Yalçınkaya, cited above, §§ 169-88).
THE COURT’S ASSESSMENT
JOINDER OF THE APPLICATIONS5. Having regard to the similar subject matter of the applications, the Court finds it appropriate to examine them jointly in a single judgment.
ALLEGED VIOLATION OF ARTICLES 7 and 6 § 1 OF THE CONVENTIONAlleged violation of Article 7 of the Convention6. The applicants complained that their convictions under Article 314 § 2 of the Criminal Code for membership of the FETÖ/PDY had violated the principle of no punishment without law under Article 7 of the Convention, primarily for the reasons set out in Demirhan and Others v. Türkiye (nos. 1595/20 and 238 others, § 29, 22 July 2025).
7. The Government reiterated their observations as outlined in Demirhan and Others (ibid., §§ 31-34). They submitted that, while notice of the present applications had been given to them as raising issues similar to those addressed by the Court in Yüksel Yalçınkaya (cited above), the Court’s considerations in that judgment had related to the specific facts of that case. They argued that the Court should therefore refrain from extrapolating the findings made therein to the present applications and invited it to assess the criminal proceedings conducted against each applicant on the basis of their own particular circumstances. They claimed, in particular, that the convictions in the present applications had not been based solely on the applicants’ use of the ByLock application, but had involved a wide variety of other evidence, not all of which had been subject to assessment in Yüksel Yalçınkaya (cited above; see the evidence listed in paragraph 3 above). The domestic courts, which had enjoyed direct contact with the evidence at issue, had established each applicant’s membership of the armed terrorist organisation on an individual basis following a careful assessment of all the elements in their specific case files.
8. The Court notes that the applicants’ complaint under Article 7 is not manifestly ill-founded within the meaning of Article 35 § 3 (a) of the Convention or inadmissible on any other grounds. It must therefore be declared admissible.
9. As regards the merits, the Court indeed observes that the evidence in respect of some of the applicants included material that was not at issue in Yüksel Yalçınkaya (cited above). That being said, having examined all the material and arguments submitted to it, the Court finds no reason in the present case to depart from its findings in Yüksel Yalçınkaya (cited above, §§ 237-72), for the reasons set out in detail in Demirhan and Others (cited above, §§ 35-47).
10. It notes in this connection that the finding of violations of Articles 7 and 6 § 1 of the Convention in Yüksel Yalçınkaya (cited above) had resulted notably from the domestic courts’ characterisation of the use of ByLock, according to which anyone whose use of ByLock was established could be convicted on that sole basis of membership of an armed terrorist organisation pursuant to Article 314 § 2 of the Criminal Code (ibid., §§ 364, 413 and 414). It therefore follows, as also underlined in Yüksel Yalçınkaya (cited above, § 414), and subsequently reiterated in Demirhan and Others (cited above, § 38), that the situation that led to a finding of a violation of Articles 7 and 6 § 1 of the Convention in that case was not prompted by an isolated incident or attributable to the particular turn of events specific to the facts of that case, but potentially applied to everyone convicted for membership of the FETÖ/PDY on the basis of their use of ByLock.
11. The Court does not rule out that there may be other evidence in respect of some of the applicants, other than their use of ByLock, that may demonstrate their organic link with the FETÖ/PDY based on the continuity, diversity and intensity of their activities and their submission to its hierarchy as required under the Court of Cassation’s case-law (see Yüksel Yalçınkaya, cited above, § 184) and thus secure their conviction as charged (see for the Convention requirements in this regard also Yasak v. Türkiye [GC], no. 17389/20, §§ 200-13, 5 May 2026). The fact nevertheless remains that the establishment of the mere use of ByLock served, on its own, as conclusive proof of the presence of all of the constituent elements of the crime of membership of an armed terrorist organisation as defined in domestic law. The Court has declared this approach of the domestic courts, which effectively imputed objective liability to the users of ByLock, to be in contravention of the principle of legality safeguarded under Article 7 of the Convention (ibid., §§ 271 and 272), and it sees no reason to find otherwise in the present case (see also Demirhan and Others, cited above, § 39).
12. In view of the above considerations, the Court concludes that there has been a violation of Article 7 of the Convention on the facts of the present case (see also Yüksel Yalçınkaya, cited above, § 272, and Demirhan and Others, cited above, §§ 39 and 46).
Alleged violation of Article 6 § 1 of the Convention13. Some of the applicants also complained that their trial and convictions for membership of the FETÖ/PDY had violated the right to a fair trial under Article 6 § 1 of the Convention, primarily for the reasons set out in Demirhan and Others (cited above, § 29). The Government argued that those complaints had not been duly raised before the Constitutional Court, either expressly or in substance, and that they should therefore be rejected for non-exhaustion of domestic remedies.
14. The Court reiterates that the main problems identified by the Grand Chamber in this group of cases in Yüksel Yalçınkaya (cited above), and subsequently reaffirmed in Demirhan and Others (cited above), was not attributable to the particular turn of events or procedural issues specific to those cases, but resulted notably from the domestic courts’ characterisation of the use of ByLock and the uniform and global approach adopted by the Turkish judiciary vis-à-vis the ByLock evidence (see Yüksel Yalçınkaya, cited above, §§ 364, 413 and 414, and Demirhan and Others, cited above, §§ 37, 38 and 42). Having already found that this approach amounted to a violation of Article 7 of the Convention in the present case (see paragraph 12 above), which will enable the applicants to seek the reopening of the domestic proceedings in the light of the principles enunciated in Yüksel Yalçınkaya (cited above, §§ 411, 412 and 425; see also paragraph 17 below), the Court does not deem it necessary to examine whether the Government’s preliminary objection under this head may be upheld in respect of each individual application concerned.
15. Accordingly, the Court decides not to examine separately the admissibility and merits of the Article 6 § 1 complaints raised by some of the applicants (see for the relevant principles Tsaava and Others v. Georgia [GC], nos. 13186/20 and 4 others, §§ 228-29, 11 December 2025; and, mutatis mutandis, Turan and Others v. Turkey, nos. 75805/16 and 426 others, § 98, 23 November 2021; and, for an application of these principles in similar circumstances, Bozyokuş and Others v. Türkiye [Committee], nos. 39586/20 and 131 others, §§ 13-15, 16 December 2025).
OTHER ALLEGED VIOLATIONS OF THE CONVENTION16. The Court notes that some of the applicants also lodged complaints under other provisions of the Convention, such as Articles 5, 8, 9, 10, 11 and 14, or raised complaints relating to other aspects of Article 6 (as in Yüksel Yalçınkaya, cited above, §§ 357, 358, 368 and 374). However, having regard to the finding of a violation of Article 7 above (see paragraph 12), the reasons for that finding (see paragraphs 10 and 11) and the specific circumstances of the case, the Court considers that it has dealt with the main legal question raised by the case and that there is no need to address the admissibility and merits of any remaining complaints (see, mutatis mutandis, Yüksel Yalçınkaya, cited above, §§ 365, 367 and 373; Turan and Others, cited above, § 98; and Demirhan and Others, cited above, § 48).
APPLICATION OF ARTICLE 41 OF THE CONVENTION
17. The Court considers, for the reasons explained in Yüksel Yalçınkaya (cited above, §§ 404, 411, 412 and 425; see also Demirhan and Others, cited above, § 53), that the finding of a violation of Article 7 of the Convention can be regarded as sufficient just satisfaction in respect of any non-pecuniary damage sustained by the applicants in the present case. It notes in this regard that the applicants have the possibility under Article 311 § 1 (f) of the Code of Criminal Procedure to have the domestic proceedings reopened following the delivery of the present judgment (see Yüksel Yalçınkaya, cited above, § 411), and that the reopening of the proceedings in a manner compatible with the “conclusions and spirit” of the judgment would in principle constitute the most appropriate form of redress, should they so request.
18. Furthermore, for the reasons set out in Demirhan and Others (cited above, §§ 54-56), the Court makes no awards for costs and expenses in respect of follow-up applications of this type.
FOR THESE REASONS, THE COURT, UNANIMOUSLY,
Decides to join the applications;Declares the applicants’ complaint that their convictions for membership of the FETÖ/PDY had violated the principle of no punishment without law under Article 7 of the Convention admissible;Holds that there has been a violation of Article 7 of the Convention;Holds that there is no need to examine the admissibility and merits of the applicants’ remaining complaints;Holds that the finding of a violation constitutes in itself sufficient just satisfaction for any non-pecuniary damage sustained by the applicants;Dismisses the remainder of any claim made by the applicants for just satisfaction.Done in English, and notified in writing on 23 June 2026, pursuant to Rule 77 §§ 2 and 3 of the Rules of Court.
Dorothee von Arnim Jovan Ilievski
Deputy Registrar President
APPENDIX
List of cases:
No.
Application no.
Case name
Lodged on
Applicant
Year of Birth
Place of Residence
Nationality
Represented by
1.
24039/21
Dönmez v. Türkiye
28/04/2021
Cemalettin DÖNMEZ
1975
Kütahya
Turkish
Engin SEMİN
2.
38590/21
Baydan v. Türkiye
27/07/2021
Cengiz BAYDAN
1986
Düzce
Turkish
Hasan TOK
3.
41577/21
Gümüşgönül v. Türkiye
06/08/2021
Nursel GÜMÜŞGÖNÜL
1984
Manisa
Turkish
4.
43601/21
Erdoğan v. Türkiye
18/08/2021
Emre ERDOĞAN
1987
Bursa
Turkish
Hasan KILIÇ
5.
48885/21
Bahtiyar v. Türkiye
17/09/2021
Gün BAHTİYAR
1982
Afyonkarahisar
Turkish
Hatice ATMAZ DERİNCE
6.
50972/21
Gözüm v. Türkiye
12/10/2021
Mustafa İlker GÖZÜM
1983
Antalya
Turkish
Zümrüt ŞAHİN
7.
56710/21
Dereçineli v. Türkiye
05/11/2021
Yaşar DEREÇİNELİ
1966
Konya
Turkish
Hamdi MERSİN
8.
59778/21
Odabaş v. Türkiye
29/11/2021
İsa ODABAŞ
1989
Isparta
Turkish
Ümmü Büşra KARAGÖZ
9.
8709/22
Topuz v. Türkiye
27/01/2022
Erhan TOPUZ
1990
Antalya
Turkish
Sultan TEKE SOYDİNÇ
10.
9420/22
Kabaş v. Türkiye
21/01/2022
Ömer KABAŞ
1975
Samsun
Turkish
Mehmet ŞEN
11.
28928/22
Kaya v. Türkiye
17/05/2022
Elife KAYA
1980
Mersin
Turkish
Mehmet ÖNCÜ
12.
43644/22
Tek v. Türkiye
20/08/2022
Tahir İsmail TEK
1989
Aydın
Turkish
Orçun MUŞLU
13.
43832/22
Aksoy v. Türkiye
02/09/2022
Hıdır AKSOY
1986
Bolu
Turkish
Muhammed Selim TÜRKOĞLU
14.
44025/22
Kurt v. Türkiye
31/08/2022
Mehmet Oğuz KURT
1981
Afyonkarahisar
Turkish
Hatice ATMAZ DERİNCE
15.
44414/22
Sinoplu v. Türkiye
07/09/2022
Emin SİNOPLU
1986
Bolu
Turkish
Muhammed Selim TÜRKOĞLU
16.
48887/22
Oflaz v. Türkiye
05/10/2022
Şafki OFLAZ
1973
Adana
Turkish
Ali Yıldırım KUZUCU
17.
49511/22
İpek v. Türkiye
12/09/2022
Yusuf İPEK
1968
Denizli
Turkish
Orçun MUŞLU
18.
50266/22
Gökcen v. Türkiye
10/10/2022
Abdullah GÖKCEN
1987
Hatay
Turkish
Dudu ERTUNÇ
19.
50465/22
Karabacak v. Türkiye
21/10/2022
Zülfü KARABACAK
1961
Ordu
Turkish
Ahmet Nihat EMEKSİZ
20.
51335/22
Cesur v. Türkiye
25/10/2022
Uysal CESUR
1970
Denizli
Turkish
Sena OLGUN
21.
51387/22
Olgun v. Türkiye
25/10/2022
İsa OLGUN
1974
Denizli
Turkish
Sena OLGUN
22.
51429/22
Ergenekon v. Türkiye
14/10/2022
Oğuzhan ERGENEKON
1988
Amasya
Turkish
Kasım ER
23.
51788/22
Ünaldı v. Türkiye
26/10/2022
Birol Tekin ÜNALDI
1973
Mersin
Turkish
Hasan Can ESER
24.
51877/22
Uçar v. Türkiye
31/10/2022
Muhittin UÇAR
1986
Kastamonu
Turkish
Esra ACAR
25.
53026/22
Şahin v. Türkiye
07/11/2022
Sümeyra ŞAHİN
1980
Turkish
Ömer KÖSTEKÇİ
26.
53097/22
Ak v. Türkiye
01/11/2022
Ahmet AK
1979
Turkish
Nuri TAN
27.
54455/22
Seylan v. Türkiye
16/11/2022
Salih SEYLAN
1982
İzmir
Turkish
Veysel SEYLAN
28.
55065/22
Mat v. Türkiye
18/11/2022
Ömer Faruk MAT
1992
Gaziantep
Turkish
Hatice ATMAZ DERİNCE
29.
56714/22
Yurdalan v. Türkiye
06/12/2022
Muhammet YURDALAN
1992
Ankara
Turkish
Hande Sernur İNAL
30.
57121/22
Öztürk v. Türkiye
02/12/2022
Melike ÖZTÜRK
1991
Isparta
Turkish
Zülal BÜKER
31.
57304/22
Sakman v. Türkiye
18/11/2022
Kemal SAKMAN
1981
Adana
Turkish
Fatih DERTSİZ
32.
57390/22
Eker v. Türkiye
05/12/2022
Hasan EKER
1973
Çorum
Turkish
Muhammet MARAŞLI
33.
2117/23
Teke v. Türkiye
15/12/2022
Mehmet Ali TEKE
1983
Adana
Turkish
Havva TEKE
34.
5366/23
Arslansan v. Türkiye
06/01/2023
Musa ARSLANSAN
1972
Kastamonu
Turkish
Meral ÖZATA ÖZGÜROL