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.
Of course, the backup plan is to have ME as your holder of private keys (see my high trust rating on bitcointalk) thus you would know
before you died..that I would fufil your wishes and blow much of it on wine/women/song and the like....and often toast your memory in
the precense of 'naked' women!