Police investigation

The police can take their time to investigate and until they are satisfied with the evidence they have in hand, it will remain in the state of under police investigation. Once they are satisfied, the will hand the case to Department of Justice (DOJ) to decide whether a criminal case will be brought to the courts.

There is no definite answer to your question as the police can take all the time they want in investigating. Even if the case was sent to DOJ and was returned for lack of evidence, the police may want to continue their investigations.

The police is under no obligation to response to reporters. But there are incidents where they will do so for pubic interest. Like there is a need for them to appeal to the public for help. Or the crime has raised a great amount of public interest.