Türkiye: Constitutional Court Clarifies Rules on Genetic Data

This is especially the case for genetic data. Genetic data can reveal extensive information about a person’s identity and biological characteristics and is therefore considered a specially protected category of personal data under the Turkish Data Protection Law No. 6698 (“KVKK”) and general data protection principles. For that reason, its retention, further use and destruction must be governed by clear and foreseeable legal rules.

In this context, the decision of the Turkish Constitutional Court dated 25 December 2025 (Case Number 2025/141, Decision Number 2025/274), published in the Official Gazette on 18 March 2026, is particularly noteworthy. The Court annulled Article 80(2) of the Turkish Criminal Procedure Code (“CMK”), which regulates that the results of genetic examinations obtained during the investigation or prosecution shall be destroyed immediately in certain cases, namely, where a decision of non-prosecution becomes final, where an objection against the decision of non-prosecution is rejected, or where there is a final acquittal or a final decision not to impose a penalty. However, the same article or CMK in its entirety does not clearly regulate what happens to the genetic personal data under different circumstances, where the law does not make it obligatory to  destroy such data; it does not specify for how long genetic personal data may be retained, whether it may be used again in future criminal proceedings, under which conditions it has to be destroyed, or whether the persons concerned may request its deletion or destruction.

The case arose from criminal proceedings concerning theft, damage to property and violation of the inviolability of the home. The key question was whether genetic data that had originally been obtained in a previous non-related case could continue to be retained and later used as evidence in a separate criminal proceeding. 

This void in the law is particularly important because, although KVKK sets out the general principles for the protection of personal data, the processing of data by judicial and enforcement authorities in the context of investigations, prosecutions, judicial proceedings and enforcement proceedings is subject to a different legal framework. It was precisely this lack of clarity that the Court considered constitutionally problematic. The Court ruled that in the context of criminal proceedings, the necessary safeguards must therefore be clearly laid down in CMK itself.

Although the Court did not explicitly ruled for the amendment of the subject article, the annulment thereof indicates that the legislator is expected to address this area in a clearer and more comprehensive manner. The decision makes clear that, where sensitive data such as genetic data is processed in criminal investigations and proceedings, the necessary safeguards must be clearly regulated within the applicable procedural framework itself. In such cases, the relevant procedural rules themselves must provide adequate safeguards and meet constitutional standards. According to the Court, a mere formal legal basis is not enough. The law must also be sufficiently clear and must include effective safeguards against excessive or improper use of data. This includes clear rules on the purpose of processing, retention periods, further use, destruction and the rights of the data subjects.

This ruling is important beyond criminal procedure law. It makes clear that the processing of sensitive personal data cannot be based on vague or incomplete rules, even in areas outside the direct scope of the KVKK. Public authorities remain bound by constitutional requirements such as legal certainty, purpose limitation, storage limitation and effective legal protection.

In practical terms, the decision means that the Turkish legislator will have to regulate the retention and destruction of genetic data in criminal proceedings in a much more precise way. At the same time, it confirms that particularly high standards apply where especially sensitive data is concerned.​​​​​