Threema messages of Marian Kočner, a contorversial Slovak businessman who allegedly ordered a murder of a local journalist, were somehow obtained with the help of Europol. [0]
The part of his trial where a security expert explained how the police got the messages was purposely not made public.
[0] https://spectator.sme.sk/c/22216551/threema-saga-kocner-repo...