Did he forget his TrueCrypt password?
Maybe he was using keyfiles?
In most European countries (that do not have specific crypto laws) you neither need to give the judge any information (except your name and address), nor help the prosecutor (i.e., the judge cannot order you to open a safe, but of course he can try to break the safe hismelf).
To answer your question directly: No, it applies to all methods of communication.
http://en.wikipedia.org/wiki/Right_to_silence#United_States
"...the U.S. District Court for Vermont ruled that because the defendant had already cooperated as far as he had and already potentially incriminated himself, by stating his ownership of his laptop and providing law enforcement with partial access to it prior to his arrest, that he must now surrender complete access to all information on that laptop, even encrypted and potentially self-incriminating or confidential information.[20] Because the defendant had cooperated in part already, the Court ruled that the defendant must continue cooperation and provide the decrypted and potentially harmful information to the government..."
It is. That's what I meant by being in custody (arrested).
or
Ignoring the details of this case, what if the court is ordering you to decrypt something that isn't even encrypted? It's just random data? They assume it is. You assume it isn't.
I suppose in this case, the fact that the someone of authority already saw unencrypted contents gives them enough reason to be confident the drive is encrypted and the defendant has the ability to decrypt it.