If you don't get satisfaction from a supervisor, don't hesitate to take it to the next step, always remembering, of course, that the victim makes the final decision about what to do. Go to the Chief if necessary. Make sure to write the full list at the bottom of the letter so everyone included knows all the others who are watching. It's always better if you can persuade a police officer or a district attorney to gather evidence and witness statements and place them in the case file. But if they don't respond to your requests there are easy ways you can do it yourself.
Most police stations have case supplemental forms available for the asking at their front desk.
Witnesses can be asked to write out their statements on these forms. The victim can also use these forms to write up additional things she feels should be included, such as the full history of abuse. Photographs, medical records, and other forms of physical evidence can also be entered by you into the case. When you have gathered the statements and any other evidence you feel should be part of the case, simply go into the police department or District Attorney's Office and ask that the items be made an official part of the case file. It's always best if you can sit down with an officer or assistant district attorney and be present so they can ask you questions about the origin of the items and so that you can watch that the evidence actually gets filed.