In at least three states, it is now illegal to record any on-duty police officer...The legal justification for arresting the "shooter" rests on existing wiretapping or eavesdropping laws, with statutes against obstructing law enforcement sometimes cited. Illinois, Massachusetts, and Maryland are among the 12 states in which all parties must consent for a recording to be legal unless, as with TV news crews, it is obvious to all that recording is underway...When the police act as though cameras were the equivalent of guns pointed at them, there is a sense in which they are correct. Cameras have become the most effective weapon that ordinary people have to protect against and to expose police abuse. And the police want it to stop...As journalist Radley Balko declares, "State legislatures should consider passing laws explicitly making it legal to record on-duty law enforcement officials."
Balko's advice, sadly, will probably not be followed. Polices officers are unionized and not getting their support easily translates into the deadly "soft on crime" label during an election. The public, in contrast, has a generally high opinion of police officers so painting yourself as questioning their honesty doesn't help you much.