If the police are policing on a public street then everything is fair game. I've always said that you are who you are wherever you are. If you are a psychopath, sociopath, or bipolar individual in your private life, it does carry over to your job whether you are in a classroom or policing on the street. There needs to be protection of the private citizens from people like this, who take pleasure in abuse of power. This may be the only time in their lives that they get to have power over others and some take it way too far. That said, the only way to even the playing field is for citizens to arm themselves with recording devices. I also welcome officers wearing recording devices as well. It truly can serve to deescalate many situations, or at the very least serve as the eyes of the truth.
Citizens most definitely have the right to defend themselves in court and a recording is the best way to do that. If the police are given absolute power, they have already proven that some of them will be corrupted absolutely! The government doesn't have the resources necessary to police the police and that means the citizens must take up the slack.
It makes sense that citizens should have the right to record the police - to avoid legal complications on both sides - though some transparency and honestly about the recording should be carried about by citizens. There's no guarantee that police will be honest or even follow proper procedure, and so citizens should have the right to monitor interactions.
By recording police, citizens are not breaking any laws, interfering with police work, and are making sure that police themselves act and conduct themselves properly. There have been too many cases in the U.S lately of police brutality and shooting unarmed black citizens and hopefully this is one way that can help to control this problem and provide evidence if needed.