And, although police and media pressure, it seems nobody who can show evidence CB did it. IMO.
But caught in the act?! Recorded in the act?! Sighted in the act?! An accomplice?
IMO he acted alone, he might even have been meticulous, lucky, solitary.
In any case, we don't know any "lateral evidence" that may have been reported to BKA. Even if not yet sufficient.
Also here in this case, his sadist pleasures of retaining his trophies (e.g. videos/photos) could have been his ruin. But he had plenty of time and even police "alerts" to destroy them.
And no final proof has came/found since the appeal, so, again, IMO BKA would just get there with his confession.