We know the evidence is weak (as in not enough to be charged) because he hasn't been charged yet.
a German judge that is very influential has said the same thing. They charge if they have compelling evidence of a crime, they haven't charged so it can't be compelling. A charge has to set out what was done, by who, where and when. If the evidence they have doesn't do those 4 things they can't charge....maybe for years.
Isn't a charge made after interview with the suspect? Or does German LE charge 1st question later?