Theres no thinking about it.. Wolters has said
Disclosure .. Double jeopardy
Possibly. I don't think so, but it's a possibility. But having no faith in your own evidence, to the point that you can't disclose it to the defence, is akin to having no evidence, or legally as good as.
He stated that he doesn't want the defence to know where the focus of their attention is / was, thereby negating the possibility of them investigating themselves and constructing an alibi. That may have been the case once, but I will guarantee that the defence know exactly what they have and don't have, nearly 2 years on.
That tactic, in my opinion, is time bound. And I believe he really thought he would have it all wrapped up within weeks of proclaiming CB as prime suspect.
Now it's clearly over, but all is not lost. This evidence he is searching for is, IMMHO, unobtainable or not physical, but by not charging him he can keep the pot simmering on the back burner. Plus, he can always proclaim that he did it - forever. He probably doesn't even need to back that assertion up, he can just refer to the 'evidence' that hasn't been tested.
He's still toast. He'll be found penning press releases for a local paper in Paderborn about cabbages, or sausages or cabbage and sausages.