Bealine
If they are caught, (and it shouldn't be too hard to work out who was sitting in the relevant seat on the previous flight or two), I hope the courts insist on a relevant sentence to ensure the lesson is rammed home!
Sadly, I don't see how a court could convict on a probability, the criminal test is beyond reasonable doubt.
It really is a sick thing to do, costs the airline a lot of money, disrupts the schedule and impacts the pax's enjoyment of their holiday.