For criminal cases, the state determines whether or not to prosecute (press charges). If they do decide to prosecute the defendant, then the victim will likely become a witness for the prosecution (they can even be forced to testify through a subpoena if the state finds it necessary). Whether or not the victim wants to press charges is not relevant to a criminal case. The state will have to listen if a victim says that they do not want charges pressed in a case, but it doesn’t mean the prosecutor will agree with them, or do as the victim asks. All victims in cases do have the right to be heard not only by the DA though, they have the right to be heard by the Judge as well.