[ben_w]

Yes, but:

1) they might not believe you, and

2) that’s still true even if the reason you don’t have a key is because you don’t actually have a secret encrypted partition — or whatever — to supply a decryption key for

So the best thing to do is avoid being in a situation where someone is allowed to do that in the first place.

[aforensics]

This is interesting. This also means that using encryption or anything that can plausibly make someone even slightly suspect you're using encryption (even if you are not) can make your situation worse, with certain classes of enemies.

I'm sure advanced configurations with well-crafted decoys and steganography can help combat that, but as we can see, encryption can only take you so far and it's only one element of the picture.