IANAL, but I don't think there's much of a difference between asking someone to reveal the correct password and asking someone to reveal the correct finger. In both cases you would be asked to incriminate yourself.
If it would be lawful for a court to ask you to "unlock the phone with the correct finger" then they might as well also ask you to "unlock this harddisk with the correct keyboard keys pushed in the correct order (as a password)".
If it would be lawful for a court to ask you to "unlock the phone with the correct finger" then they might as well also ask you to "unlock this harddisk with the correct keyboard keys pushed in the correct order (as a password)".