Demirer v. Türkiye, No. 45779/18, ECtHR (Second Section), 25 March 2025

The conviction of an individual for membership in a terrorist organization, based on a thorough and reliable assessment of the evidence and supported by well-reasoned arguments, does not amount to a violation of Article 6 of the European Convention on Human Rights.

Art. 6 §1 ECtHR

1. Membership in an armed organization of an extremist character may give rise to criminal liability, provided that the national court’s decision is supported by adequate and reasoned justification. Such justification is deemed sufficient when it articulates, clearly and in detail, the grounds on which the judges found the individual guilty, taking into consideration both the evidentiary record developed during the proceedings and the defense arguments presented by the accused.

2. In criminal proceedings concerning terrorist-related offenses, the reasoning accompanying a conviction is considered sufficient even if it does not address each individual defense argument; it suffices that the decision clearly identifies the decisive elements of the case and the rationale underpinning the assessment of the credibility of the various pieces of evidence. The principle of reasoned decision-making enshrined in Article 6 § 1 of the ECHR requires, as a minimum standard of protection, that judicial decisions be both comprehensible and non-arbitrary, highlighting that the reasonableness and transparency of the decision-making process are fundamental pillars of a fair trial.

3. In fulfilling its interpretative role, the European Court of Human Rights cannot substitute itself for the domestic courts on matters of merit; it is limited to assessing whether those courts have properly exercised their judicial authority and discharged their obligations to provide reasoned decisions. Such compliance cannot be evaluated in the abstract but must be examined in the context of the entire decision-making process, the evidentiary framework actually relied upon, and the rigor of logical transparency. In this respect, the Convention judge does not function as a mere appellate supervisor, but must focus on the adequacy and persuasiveness of the reasoning rather than on its formal exhaustiveness.