Plausible deniability http://www.truecrypt.org/docs/?s=plausible-deniability

UK jails schizophrenic for refusal to decrypt files http://www.theregister.co.uk/2009/11/24/ripa_jfl/

Well they could, but why would I give them If I seriously had something dangerous in my PC? Though I've secured my system more for theft, though It would be good to have guest account which could login normally, so that the thief would not just reformat the drive right away and I could actually trace the thief when he's using the PC before reformatting like some of the success stories, but more than that I don't want my files to be seen.

Not if you forgot it.

Actually in the UK you can be detained indefinitely even if you plead that you forgot it.

That scares me. I've forgotten half my Truecrypt passwords. I guess I should give up and delete those archives.

Plead the Fifth!

I think you're joking, but for what it's worth, that doesn't work. You can claim that the encryption key itself contains self-incriminating data, but then they'll simply say "ok, we completely understand. Go ahead and type it into your laptop and decrypt the data and you don't have to reveal the key."

Your honor, it has been more than six months since I was arrested and I can no longer remember the encryption key. All I can remember is that it twenty random letters/numbers.

Even if you lie in court it is very difficult to prove it.

A broad interpretation of the 5th would mean you don't have to assist the authorities in any way in convicting yourself of crime.

right to remain silent. Orally, in writing, keyboard typing, or through any other means of communications.