What constitutes illegitimate surveillance of state troopers?
In a landmark ruling, the First Senate of the Federal Constitutional Court in Karlsruhe has set new limits for covert surveillance to clarify criminal offenses, particularly those that are serious or particularly serious. The decision, made in response to a constitutional complaint initiated by the association Digitalcourage in 2018, aims to strike a balance between the need for effective law enforcement and the protection of fundamental rights.
The ruling specifically targets the use of source-TKÜ, a method that involves recording a suspect's communication, such as telephone, email, or chat messages, before or after they are encrypted. This form of surveillance is considered a very serious infringement on fundamental rights, allowing the tapping and evaluation of the entire raw data stream.
The court explained that the source-TKÜ is a severe interference with privacy, thus requiring the offense to be particularly serious to justify such intrusion. The law enabling secret online searches was declared unconstitutional due to a formal deficit: it did not correctly specify which fundamental rights were being restricted, violating Article 19 of the Basic Law by insufficiently addressing the secrecy of telecommunications under Article 10.
As a result, police and prosecutors may no longer use state Trojans (source-TKÜ) to secretly install software on digital devices for offenses punishable by a maximum of three years or less in prison, effectively banning their use for minor crimes or "everyday crime."
The current legal framework remains temporarily in force to avoid investigation disruptions but must be promptly revised to align with constitutional standards. The legislator is required to revise the laws to clarify and limit the scope of such surveillance to serious crimes and to specify all fundamental rights involved, ensuring constitutionally compliant use.
Despite the Court's ruling, the utilization of state trojans in serious criminal investigations continues, and the number of authorizations for source-TKÜ surveillance has been increasing, with over 100 such orders granted in 2023 alone.
The ruling reflects concern that source-TKÜ surveillances, where communications are intercepted directly at the end device before encryption, pose significant risks to fundamental rights and digital security. Critics highlight the inherent conflict in state hacking tools: while intended to aid law enforcement, they require exploiting or maintaining security vulnerabilities, potentially exposing all IT systems in Germany to threats beyond just targeted suspects.
The ruling is a significant step towards ensuring that the rights and freedoms of German citizens are protected, while still allowing for effective law enforcement. It serves as a reminder of the importance of striking a balance between these two crucial aspects in any democratic society.
[1] Federal Constitutional Court, 1 BvR 2466/19, Judgment of 24 June 2025 [2] Federal Ministry of Justice and Consumer Protection, Annual Report on the Use of Technical Measures in Criminal Proceedings, 2023 [3] Digitalcourage, Statement on the Federal Constitutional Court's Ruling on Source-TKÜ, 25 June 2025
- The ruling made by the First Senate of the Federal Constitutional Court in Karlsruhe highlights the need for policy-and-legislation to strike a balance between effective law enforcement and the protection of citizens' data-and-cloud-computing rights, particularly in regards to cybersecurity.
- The utilization of state Trojans (source-TKÜ) for minor crimes or "everyday crime" has been effectively banned following the constitutional court's decision, which highlighted concerns about privacy and digital security.
- The Federal Constitutional Court's ruling on source-TKÜ surveillance underscores the critical role of politics in shaping policy-and-legislation that ensures the protection of citizens' fundamental rights, while also enabling effective law enforcement in the era of technology.
