"To the courthouse to file cases against you."
And then actually do it.
That's a good one, but I told him to say, with a smile: "Am I free
to go now?" and patiently wait for an answer.
I didn't tell him the part where you're told you're 'under
investigation', and you reply: "What's the nature and scope of your
'investigation'?", and patiently wait for an answer. They COULD make
shit up but typically they're just looking for a victim, will check
your ID and go away.