Under RIPA if you can prove that you no longer posses the decryption key, you don't have to go to jail. That's not as easy as it sounds, since being a possession of the key "previously" makes the law assumes you still posses the key, but at least you have a chance...

That's a step up from the French key disclosure law, where you go to jail regardless (no backups? your HSM is dead? tough...)