Re: It's not encrypted...
I just read of a recent case ruling determined that biometric keys such as fingerprints could be used to unlock a phone, but NOT passwords.
This is still being argued case-by-case (more for living suspects) in various US jurisdictions (state and national courts). it does seem to be more acceptable in cases of immediate aftermath of a crime with high likelihood of probable cause.
But then there is also the 4th Amendment protecting from "unreasonable" search/seizure of private papers, but that does allow "reasonable" (for a warrant), so that could be argued case-by-case as to what's reasonable I suppose.