My job requires me to carry a voice operated micro recorder.
I have since found that it is feared by many police officers. Only had the opportunity to use it once ( against the police) when I was a passenger in a car which had been pulled over by an over-zealous police officer.
Many police carry the things themselves but don't turn theirs on until it suits them....I recorded the total conversation including similar threats as those mentioned by albanycobra.
The driver of the car in which I was passenger did not receive a ticket and the officer involved didn't have to front the Police Complaints Tribunal or the Commissioner.