Police cannt be witness to criminal cases;
in your case few SPEED post letters and RTI can do wonders.
they cannt write to your working place.
if Police gives witness and calling your Office, with all details drop a Speed post to SP/IGP/DIG asking them to take disciplinary action against Police and after a week file RTI asking them the status of the complaint.
just browse this link, [ http://mynation.net/abio/ ] and you will know how to write such letters more details