Simple. Don't get arrested. (Easier said than done, but millions of people manage to do it.)
There was an article today that talked about how ~1/3 of American adults have been arrested in their lifetimes, but a large number of those people are not even charged with any crime.
The only real way to keep your BTC safe in the event you get arrested and/or get sent to jail/prison is to use a brainwallet. Any other method would result in the possibility of the private key be stolen/found, and your privacy is significantly reduced if you are sent to jail/get arrested.
I've been arrested (drunk and disorderly, pissed in my old cat collecting neighbors front door mail slot) but they charged me and let me go when I sobered up.
I dunno, the QR on ur stink hole is a pretty good hiding spot. After a few years in prison it might be a little hard to read though.