I assume that if you deliberately do anything to alter the state of the device in policy custody as evidence it will be considered tempering with evidence. A s

I assume that if you deliberately do anything to alter the state of the device in policy custody as evidence it will be considered tempering with evidence. A similar analogy - "hey, I didn't destroy evidence, I just remotely instructed my phone to encrypt itself. The data is still there, it's not destroyed." That would land you in a federal prison real fast, and rightfully so - you took action to change the device state after it entered police possession and you knew it was evidence. The contents of the RAM would definitely be considered evidence since by your own explanation they contain the data that the police are looking for.