Cant see you going to prison,i wouldn't worry about the guy been a policeman,I would keep asking the police to charge this man with common assault,if they wont ask why and get their reply in writing from someone upstairs,i would also inform the police at your next meeting that if this case proceeds you will produce in court a signed affidavit stating the above facts Affidavits are powerful in court and shows the police you mean business if this charge is not dropped,also let them know you will also look into tort law and further actions against these persons if this case proceeds.