Using an encrypted messaging app isn't enough evidence of terrorism, Europe’s top rights court rules

AMSTERDAM (CN) — Turkey violated the right to a fair trial of 239 people convicted of terrorism by relying on the use of an encrypted messaging app as decisive evidence, the European Court of Human Rights ruled Tuesday.

The decision builds on Yüksel Yalçınkaya v. Türkiye, a high-profile ruling where the court’s Grand Chamber found the mere use of the ByLock app, which the government associates with the banned Gülen movement, was not enough to justify a terrorism conviction. Such blanket assumptions violated core legal safeguards, the court said.

The case ties back to Turkey’s mass purge following a failed military coup in July 2016. The government blamed the plot on Fethullah Gülen, a U.S.-based cleric and former ally of President Recep Tayyip Erdoğan.

Gülen lived in self-imposed exile in Pennsylvania from the late 1990s until his death in October 2024. He consistently denied any role in the attempted coup.

One of the main tools used to link individuals to the Gülen network was ByLock, an obscure encrypted messaging app that prosecutors said was developed specifically for followers of the movement. Turkish courts often accepted its use as sufficient evidence of group membership.

In the months that followed the coup, more than 100,000 public employees were dismissed under emergency decrees. Tens of thousands of people were arrested or prosecuted over accusations of ties to what the government called the Fetullahist Terrorist Organization, or FETÖ. Judges, prosecutors, military officers, teachers, journalists and civil servants were among those affected.

In this case, the applicants were convicted based on technical data showing they had downloaded or used the app, following a similar pattern seen in the Yalçınkaya judgment.

The Strasbourg court found that Turkish judges treated the use of ByLock as automatic proof of full membership in the group. It said the domestic courts failed to examine what kind of communication took place, the user’s intent, or whether the individual had any link to the group’s internal structure.

“The establishment of the mere use of ByLock would serve, on its own, as conclusive proof of the presence of all of the constituent elements of the crime,” the court wrote.

Such reasoning, the judges said, violated the core legal principle that individuals cannot be punished for conduct that wasn’t clearly defined as criminal at the time. They further held that the proceedings failed to meet basic standards of fairness under international human rights law.

Turkish prosecutors’ handling of digital evidence also raised concerns. Ankara judges relied heavily on user IDs and IP addresses extracted from the ByLock server, cross-referenced with national internet data. Yet defendants, the court said, had little opportunity to challenge the accuracy or context of that evidence.

Highlighting broad procedural shortcomings, the court concluded: “The domestic courts’ failure to put in place appropriate safeguards was incompatible with the very essence of the applicants’ procedural rights.”

Turkish officials also cited additional evidence, such as bank records and witness statements. But the court said these were often secondary, used mainly to support the presumption based on ByLock use.

The judges also weighed Turkey’s state of emergency after the 2016 coup attempt, which temporarily limited certain human rights protections. But even in times of crisis, they said, the right to a fair trial and the basic rule that a crime must be clearly defined in law cannot be set aside.

The judges said that recognizing the rights violations was enough to address the harm suffered. Although some applicants asked for financial damages and repayment of legal fees, the court declined, pointing to the repetitive nature of the case and broader issues already covered in the earlier ruling.

Six of the seven judges backed the decision, which opens the door for domestic courts to revisit the convictions if requested. Judge Saadet Yüksel dissented. In a separate opinion, Judge Oddný Mjöll Arnadóttir agreed with the main judgment but said it was unfair to deny legal cost reimbursements to those who had brought their cases before the earlier precedent was set.

The case adds to a growing line of rulings examining Turkey’s sweeping post-coup prosecutions. The court noted that thousands of similar cases are still awaiting judgment.

The Turkish government did not respond to a request for comment.

In an effort to assert national identity on the international stage, the country formally adopted the name “Türkiye” in 2022, asking foreign governments and media to use the Turkish-language version in official contexts.

While the ruling is not yet final, both the applicants and the Turkish government may request a referral to the court’s Grand Chamber within three months. If the judgment is upheld, individuals could seek to have their criminal cases reopened under domestic law.