Dash cams in most/many/some police cars work when the officer engages his lights or sirens, passes a certain speed threshold, etc.
It's my firm belief that the men and women serving in our police force should, for example, be allowed to pee, eat a sandwich, or talk to their partner about how bad their mortgage company is without being recorded -- but at the same time, it's my firm belief that their enforcement should be documented.
Start by expanding the dashcam FOV and expand the triggers for dashcam recording to include a period of time after the opening and closing of the doors.
How to let officers pee without also letting them turn off cameras at every "inconvenient" time presents a challenge...