If they know for sure that you have a lot of Bitcoins and are willing to torture you to get them, you are pretty much screwed.
The main option, if you don't want to hand over your private keys and secure your coins, is to be always able to kill yourself instantly (say, by having a poison pill in one of your teeth or so). This secures your keys.
This is why non-anonymous crypto is fundamentally flawed, because you transfer the danger of getting stolen, into the danger of getting tortured, if the knowledge of your possessing crypto is public.