[Eustace the Monk]

The cheating is noticed when the card you swap into play ends up matching the card another player, NPC, Dealer, or table holds. This can even happen if everyone folds and it matched one of the folded cards. Cheating in Blackjack is much easier, as there tends to be fewer cards in play (with fewer people playing). With only the one NPC and Dealer to contend with, the odds of matching a card are much more in your favor. In poker, with just the NPCs, you have a total of 17 Cards in play (if the programming accounted for burn cards.

One thing I noticed, if you notice you got caught before the game announces, leave the table. You end up not getting fined or going to jail, then you get to sit right back down. Happy cheating to you all.