This is common practice. In criminal cases, information on parties to the proceedings, summons, petitions and appeals is available under embargo for inspection by journalists at the latest one week prior to the hearings. The embargo applies until the start of the public hearings of the case. That is the formal start of the investigation for the hearings. At that moment it will publicly be determined who has appeared.
A law firm has been reported
A law firm has recently been reported for the defendant(s). The District Court of The Hague will not release the name of the firm and does not specify for which suspect(s).