I think there's more to merely 'collecting additional evidence' at work here with HCW.
He clearly thinks he has some compelling circumstantial evidence, but yet he waits.
Two issues spring to mind - what was the term of his latest conviction, 7 years? In Germany it's likely he'll do a third of that, due to their stance on rehabilitation. He's done at least a year, maybe more. I'm not saying he'll be released, just that his eligibility for parole is a milestone that's pending.
Then there's the issue of a fair trial, i.e. he won't get one. There must be high level machinations going on trying to square the circle HCW has created with his continued, public proclamations of CB's guilt.
I'm not legal expert (...cue the Stewart Lee bit about the Loch Ness monster "I don't know anything about zoology, biology, geology, geography, marine biology, cryptozoology, evolutionary theory, evolutionary biology, meteorology, limnology, history, herpetology, palaeontology or archaeology but I think; what if a dinosaur had got in the lake").....but I don't think it's possible for him to get a fair trial. A trial will never happen.