Like jbg said in another comment here, the legal system doesn't work that way, where the prosecution can claim you did stuff and you have to disprove the claim. The burden of proof is on the prosecution.
So you are agreeing with me that this tactic of plausible deniability with multiple encryption keys works then?
Which is it? Does encryption allow you to hide from the law, or can innocent people just be proclaimed that they are hiding something and that they have to give up keys that don't exist?
It is one or the other, because encryption plus multiple keys makes you 'indistinguishable' from an innocent person who truly cannot give you a key that doesn't exist.
The tactic might work, but how well it would work would depend on what other evidence was presented that you do have another encrypted area. For example, if they analyse the partition you gave them the key to and show that it hasn't been booted in 18 months; they cross-reference the cached DHCP leases with the times you were known to have been online using that machine and find discrepancies; they might even have secretly imaged your disk a month earlier and show that a large amount of supposedly free space has changed content in the meantime.
(Maybe they even have you recorded telling someone that you have a second encrypted area on the machine.)
If there's no such evidence, then it ought to be pretty hard to convict you.
