> Miranda also claims that he didn't know what he was carrying, despite assisting his partner, visiting this film-maker, and knowing all the passwords!

Why is this impossible? Of course he knows his mobile phone and laptop password. It's entirely possible, though, and maybe even likely, that he doesn't have the decryption passphrases for the data he's couriering on them.

People hosting a Tor node do the same thing - they transport data without knowing what's in it.