Consider the demand curve for fare evasion on a train. The price (I suppose) would be the average amount of money paid per ride in fines, and the quantity would be the average number of fare evaders caught. The supply curve would quantify the target number of fare evaders to catch.
Normally technological advances push the supply curve rightward. This would correspond with more people getting caught.
But this obviously isn't right. If it were easier to catch fare evaders, you'd intuitively expect that the average price in fines per ride for a rider would be higher, thus, quantity would go down.
What does the supply/demand curve really look like for fare evasion and what would be the effect of a rightward supply curve shift?