Slate has it pegged in this fictitious report by an undercover cop of the future:
At 1217 hours, I saw suspect swipe his hand under the divider for a few
seconds, a possible sign of support for charter schools. Suspect
repeated this motion again, from the front towards the back, and I
could see more of his hand. Suspect then swiped his hand in the same
motion for a third time. My experience has shown that this suggests an
openness to publicly funded private school vouchers.
Did he make an arrest?
Suspect denied all charges and claimed he was really soliciting homosexual sex. He was immediately released.