Are you breaking the law when you record encounters with police officers?  Apparently, you are in Maryland.  In Tennessee, however, I would argue that Tennessee Code Annotated sec. 39-13-601(b)(5) applies:

It is lawful under §§ 39-13-601 — 39-13-603 and title 40, chapter 6, part 3 for a person not acting under color of law to intercept a wire, oral, or electronic communication, where the person is a party to the communication or where one of the parties to the communication has given prior consent to the interception, unless the communication is intercepted for the purpose of committing any criminal or tortious act in violation of the constitution or laws of the state of Tennessee.

In any event, it is absurd to say that a police officer on duty in public has some expectation of privacy, where the person he is encountering does not.