Wishful thinking. Aircraft are designed to be operated by professional crews -- not ex-convicts on work release. So, there are accessible circuit breakers to turn various things off.

It's called a circuit breaker. Just about every system, include the flight recorders, autopilot, and transponders can be independently turned off.

I did some research on this, expecting to find a breaker labeled "CVR" on the diagram of 777 cockpit circuit breakers. Instead I found this: "the practicalities of isolating the power from the CVR fitted to the B777 are not straightforward since the CVR circuit breaker is located in the electronics bay of the arcraft instead of on the flight deck. Access to the electronics bay from within the aircraft is via a hatch in the cabin floor adjacent to the front left door of the aircraft"

http://www.aaib.gov.uk/cms_resources.cfm?file=/Boeing%20777-...

@danford was asserting that he didn't think there would be switches in the cockpit that allowed all tracking devices to be turned off. Are you countering his statement? Can you provide a citation?