Investigators will say "you sent this email to your dad at 09:29 on Tuesday, yet it wasn't sent from your phone or laptop according to device logs. You either have another device you haven't given us, or you haven't decrypted the right partition".
Bootdrives with no cache are the perfect answer to this through a lawywe."USB boot drive. There are no logs kept to it. I'm not hiding anything, it is just good sense to use a computer which doesn't persist any state limiting any malware to session only in the very worst case."
You sent shit to your dad from the wrong machine/partition.