Good question. There’s a database somewhere with the answer.
I already realized it wouldn't work.
All they have to do is make a backup image of your hard drive before they enter the password.
Then you are just shredding a copy.
Truecrypt has a decent alternative; a hidden encrypted volume inside of another encrypted volume.
You give them the password to the outer volume. There is no way to know that there is an encrypted inner volume, so your data is safe and they don't even know it is there.