Doesn't look like Filevault has a duress option— otherwise it'd be pretty nice to have a separate password that boots you to a dummy partition showing a fresh desktop install with apparently nothing on it. For bonus points, you could have the dummy OS kernel-patched so that it doesn't even show the other partitions as existing, and just pretends it's occupying the whole disk with mostly empty space.
"That computer? Oh yeah, I just picked it up, officer; was going to start configuring it when when I arrive at my destination."
"That computer? Oh yeah, I just picked it up, officer; was going to start configuring it when when I arrive at my destination."