Whether the prosecutor could order joinder of the investigations against B.________
The joinder was proper, because B.________ was accused of several offenses and joint prosecution was required under Art. 29 al. 1 let. a CPP.
Art. 30 CPP was not the relevant basis in this situation; it extends joinder only to other cases, while Art. 29 al. 1 let. a CPP directly applies when one accused committed several offenses. The prosecutor's reference to the wrong provision did not affect the correctness of the decision.