Why do they need that? All they need is for a policeman to physically seize a device while it is unlocked. Or even while it is locked with encryption keys sto

Why do they need that? All they need is for a policeman to physically seize a device while it is unlocked. Or even while it is locked with encryption keys stored in memory, and some custom tech to read the RAM from a running device. I'd wager that people with sufficient physical security to prevent this are very rare, and it works against any sort of device that doesn't have a dead man's switch.