German police are accused of illegally using a coronavirus tracking app in a criminal case to find witnesses. The measure was widely criticized by the police and German prosecutors launched an investigation.

The Mainz police allegedly used the Luca app illegally in a crime case at the end of November, meldt SWR. A man fell dead shortly after leaving the restaurant. Authorities obtained the unencrypted data from the health service and used it to track who was in the restaurant at the time of the crime. In the end, 21 potential witnesses were found.

The app’s developers have since released a statement denouncing the activities of the police. Several German politicians, including members of the current coalition, also spoke about the matter. Some are asking to delete the app, Handelsblatt writes.

The Luca app keeps track of how long German users spend in restaurants or other public places. In those cases, the QR code must be scanned. When a user is infected, it is easy to keep track of where they have been and for how long. Users must provide their full name, address and phone number in the application. Personal data is encrypted and may only be decrypted by the local health service if the source of the infection has to be traced. The relevant public site must give permission for that as well.

Luca is a special initiative as an alternative to paper registration of visitors, for example, catering. With the German government’s Corona-Warn app, it is not possible to check who is in a particular place at a certain time. Just like the Dutch CoronaMelder, this works with bluetooth signals via the Google and Apple API and doesn’t save any location. Moreover, Corona-Warn and CoronaMelder do not contain any personal data of the users.

“The current case is very serious because the legal prohibition on the use of contact tracing data for police purposes is clearly and unequivocally enshrined in the Infectious Diseases Act,” Stefan Brink, a data protection officer in Baden-Württemberg, told Handelsblatt. “It’s hard to believe the safety authorities have waived the ban in this case.” The police force has apologized and said it will no longer use the data. German prosecutors have launched an investigation into the breach of privacy for the police.

Update 16:20: The article said it was about potential perpetrators, but it was about potential witnesses. In addition, the explanation for the Luca app has been expanded and information about the relationship with Corona-Warn has been added.