Two years ago I posted an article that has been fairly popular, Encryption and Key Demands. The phrase 'duress key' seems to drive the traffic there, even though I'm not the one who coined the term. Anyway, a real-life example of that has shown up.
UK jails schizophrenic for refusal to decrypt files
You don't fork over your decryption keys on demand, you get jail time just for that! As I said two years ago, this is a lot harder to pull off in the US due to that whole Bill of Rights thing. Harder, but not impossible.