It is recommended that you always film the police. Even if you're not the person they are dealing with. This helps keep the truth preserved and protects EVERYONE involved. From the suspect to the officer, camera's dont favor and are non bias. So always film the police, trust me, they are filming you.
Filming The Police
YOU HAVE THE RIGHT TO FILM THE POLICE - In all 50 states except Illinois, you have the right to film the police during the course of their duties provided that you remain at a safe distance, do not physically interefere with their duties, be on public property or your own property, and if you are on private property, you must have the property owners permission. Police can NOT tell you to stop recording, the can not make you leave if other members of the public (without recording) are allowed to stay. They CAN order you to back up. If you are going to record the police, do it in an open and obvious manner. Under the 1st ammendment there are no circumstances where the contents of video or photographs should be deleted or destroyed. Source - Washington Post