It is worth noting that so called
Similar Fact Evidence (MO) is generally presumed inadmissible in common law countries (e.g. UK)*. That is because of the danger of propensity reasoning.
So for example the fact that the suspect has priors for sex offences and rape is not directly relevant in an abduction/murder case. You can't argue that CB is "the type of guy" who would do this (propensity reasoning). Whereas in the prospective HB prosecution, you can make an argument that the MO of the rapist is so similar to CB's rape of the American woman, that the probative value outweighs prejudice.
IMO the difficulty is that we don't have an MO in the MM case, and it doesn't fit with a burglary or violent attack. Perhaps the prosecutor can argue/prove that CB had burgled OC before and that therefore is powerful evidence to the prosecutors theory.
But all of this depends on having some other piece of evidence that ties CB directly to the murder IMO. It won't be enough that he fits a profile.
* usual disclaimers about Germany not using an adversarial jury system and different rules of evidence applying. In the end, how judges weigh evidence is the same.