Conversation so far:
When was Mielke imprisoned?
1989.
What crime was he convicted of?
ruling that Mielke was not mentally fit to stand trial.
How long was Mielke imprisoned?
1,904 days.
What happened during his imprisonment?
Mielke enjoyed having imaginary conversations with non-existent Stasi agents.
Are there any other interesting aspects about this article?
[Mielke's] bank account, which held more than 300,000 marks (about US $187,500), was confiscated.
What did Mielke do after being released from prison?
all further prosecution of Mielke had been indefinitely suspended.

Question: What else is interesting about his imprisonment?
Self-contained rewrite: Besides the conversations with imaginary non-existen Stasi agents and his bank account being confiscated, what else is interesting about Erich Mielke's imprisonment?