It sounds to me you are being dragged into a situation between to warring sides. However, I would still recommend you contact an attorney at least for a consultation, if nothing else. Most officers are doing there best to prove up a case, but you do have a right not to communicate with them in certain situations. I would recommend trying to sit down with a lawyer and go over your options.
If you are subpeoned as a witness in case, you have to respect that subpeona or else you open yourself up to penalties on your own. I would recommend talking with an attorney that can give you a full consult on your situation.