The judgment of the Grand Chamber of the European Court of Human Rights (ECtHR) in Yüksel Yalçınkaya v. Türkiye was the first decision to call into question, on such a scale, the legal basis of the convictions handed down under Article 314 of the Turkish Criminal Code (TCC) after 15 July.

The ECtHR found that inferring all the elements of the offence from the use of ByLock breached the principle of legality in criminal law, and that the inability of the defence to test this evidence breached the right to a fair trial.

The judgment in Demirhan and Others showed that the problem, described as systemic in Yalçınkaya, had recurred in a further 239 applications, while the Yasak judgment made clear that the same criteria also apply to convictions based on evidence other than ByLock.

The most important authority for determining whether these judgments have found any reflection in domestic law is the Court of Cassation.

It is the 3rd Criminal Chamber and the Plenary Criminal Chamber of the Court of Cassation that decide whether membership convictions become final, by which criterion the trial courts are to rule again in quashed cases, and within which case-law framework requests for the reopening of proceedings based on ECtHR judgments are to be assessed.

Our earlier study on the individual application decisions of the Constitutional Court, entitled “Apparent Redress, Continuing Violation”, showed that the Constitutional Court summarised the Yalçınkaya and Yasak judgments but did not apply them. The present study asks the same question in respect of the Court of Cassation.

The study examines the texts of 26,947 decisions delivered by the 3rd Criminal Chamber and the Plenary Criminal Chamber of the Court of Cassation between 1 October 2023 and 22 October 2026 and published in the official case-law database of the Ministry of Justice.

The examination was not confined to membership convictions; it also covered decisions on appeals against judgments concerning aiding, leadership, propaganda and acquittal.

Each finding is supported by the date, docket number and decision number of the relevant decision, and wherever possible the key passages of the decision are quoted verbatim. The aim is to enable the reader to verify every assessment against its source.

The title of the study summarises the resulting picture. The Court of Cassation quashed more than eighty per cent of membership convictions. Yet the great majority of these quashing decisions did not alter the criterion identified by the ECtHR as the source of the violation; on the contrary, they reiterated that ByLock use, once technically verified, would constitute “decisive” evidence for a conviction and remitted the case so that this verification could be carried out.

The quashing of the judgment did not mean the quashing of the criterion.

This study has not been prepared as a general criticism of the Court of Cassation, but as a reading of the Court of Cassation’s own decisions, and of the criteria found in its own case-law, in the light of the ECtHR judgments.

Indeed, a significant part of the contradictions identified stems from the fact that the Court of Cassation does not apply in its decisions upholding convictions the criteria it applies in its decisions quashing them in the defendant’s favour.

This shows that case-law consistent with the Yalçınkaya and Yasak judgments is also possible within the Court of Cassation’s own body of jurisprudence.

The study is intended to serve as a useful resource for lawyers and defendants dealing with these cases, for academics, and for the Committee of Ministers, which supervises the execution of the Yalçınkaya group of judgments.