Assuming you're talking about the US, you're slightly mistaken. The police just use the phrase in the colloquial sense, as a way of asking if you'd co-operate with a prosecution. The actual report gets written up then goes to the DA's office. The DA's office ultimately makes the call. Your cooperation is a big factor, but it won't force their decision. A private citizen doesn't have the authority to force the DA to bring charges if the DA decides it's not worthwhile.