It depends on the case and the prosecutor filing the case. When I was a prosecutor, I was trained to review all of the evidence available to me before filing any case. I had to ask myself two questions when deciding whether to file charges: First, was I convinced beyond a reasonable doubt that the accused person had committed to offense(s) and secondly, whether I had a reasonable likelihood of proving guilt beyond a reasonable doubt at trial. If both of those questions were answered in the affirmative, then I filed the case. Sometimes the police bring in a request for filing to the DA's Office, but the DA doesn't think there is enough evidence and will either reject the filing with a request for further investigation, or simply reject the request totally and bring no charges whatsoever. I hope this helps.