Dash cams and cell phone dumps can be used against you, but I think they must ask to look at them, and if you refuse, they have to get a warrant. (I think, but not certain, and this is also a matter of individual PD policy).
Last fall, we had two women drivers do a head on in my 25mph subdivision drive, in daylight.
I went out to talk to the cops, and said someone had to be on their phone, did you dump them? He said probably so, but we don't mess with phones when there is minimal human damage fender benders.
So just like talking to the cops, you do so at your own risk, and the same with consenting to searches. It's generally a bad idea even though most of us law abiding types like to cooperate with good policeman everywhere.
If it's a bad one with potential (civil and/or criminal) liabilities, it's best to politely not cooperate. Or give a general denial of fault, but don't answer questions. If they say they will hold you until they can get a warrant, the answer is....
OK, I'll wait if I have to (because usually that's a hollow threat, with no instant warrant possible).
