In message , at 17:15:08 on
Tue, 15 Jul 2014, David Walters remarked:
It's possible I have a knowledge gap about the card technology and
cards can be checked in some way that I'm unaware of.

I don't think the cards can be checked, but in theory an online gripper
could ask the back-office if they've seen any flying pigs delivering
that card number and an associated touch-in recently.

Perhaps you can't tell by interrogating the card but you could log all
contactless cards that passengers claim to be using and then as part of
the overnight processing bill any cards that were checked by an inspector
but hadn't started a journey with a penalty fare.

Although that would leave the system open to abuse by people with pre-paid
cards, assuming they can be used at all and they aren't registered to
an individual.

And the reverse, which is accidentally giving the gripper the "wrong"
card and hence creating an unresolved journey when in fact you had
touched in with another of your cards.
--
Roland Perry