Would you, under immediate threat, be able to locate and destroy the memory chips—and specifically the memory chips—on your phone? If they're prepared to lock you up for 10 years, they're prepared to do some serious digital forensics on some unsnapped chips.
Would factory resetting your phone be sufficient, or is data still recoverable even after the standard factory reset option on Android (and I assume, iPhones)? I don't really know much about these "serious forensics."