[tremon]

it's a lot cheaper to run a camera waiting to record than recording all the time

That does not mean the decision to run the camera should be in the officers' hands though. It should be possible to design an algorithm that automatically starts and stops recording based on officer location (like "shut off the camera when the officer is facing a car dashboard").

Then there's also the option to continuously record audio, even when video recording is turned off. There's so many better alternatives than "give the police officer discretion over when to hide their actions".