*Spoilers* The Torture Victims

[superluser]

So maybe he was able somehow to declare many people as guilty of something, perhaps with a little help of the Black Eagle?

That puts him in the same situation. People ask too many questions if you have that many more capital offenses in your province. On the other hand, he could offer to accept prisoners from other provinces to execute there. That's not very believable, but it is plausible. The Reindel family did supposedly carry out all executions in Prussia during the time in question, so simply substituting Alexander for Reindel would carry you most of the way there (note that I don't have any reason to suspect that only one Reindel did all the executions or that they were al shipped to his home, so you'll still have to do some heavy lifting for that).