Edge sorting is a technique used in advantage gambling where a player determines whether a face-down playing card is likely to be low or high at casino table games by observing and exploiting subtle unintentional differences on the backs of some types of card, after persuading a croupier to cooperate by unwittingly sorting the cards into low and high.
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A judgment of the UK High Court ruled that the technique, which requires the player to trick the croupier into rotating cards, is cheating in civil law, and that a casino was justified in refusing payment of winnings; this ruling would not be applicable if the player simply took advantage of an observed error or anomaly for which he was not responsible in, say, the backs of the cards.
Technique
Many packs of cards produced by manufacturers have unintentional edge irregularities. Typically all the backs of the cards in such a pack are identical, but the two long edges of each card are consistently distinguishable: the pattern is not symmetrical to a 180° rotation (half a full turn). During the course of a game, a player will ask the dealer, a casino employee, to rotate some face-up cards, perhaps saying they feel it will bring them luck. The dealer does not realise that cards are being turned so that low cards, typically 6, 7, 8, or 9, are one way round, high cards the other way round, and that the edges are different. The dealer is also asked to shuffle the cards with an automatic shuffler, which does not change the orientation as a manual shuffle may do. The dealer is not obliged to comply with these requests, but will usually do so if thought to be due to gamblers' superstition or mistrust. Over the course of a game, low cards will tend to be oriented one way, high cards the other. Once a significant proportion of cards have been rotated, any player who knows this can gain a statistical edge more than outweighing house edge by using the knowledge whether the card to be turned is likely to be low or high.
Legality
Casinos usually regard this technique as cheating; many players consider that they are legitimately playing to gain an advantage.
In 2012 poker player Phil Ivey won US$9.6 million playing baccarat at the Borgata casino with partner Cheung Yin Sun. In April 2014 the Borgata filed a lawsuit against Ivey for his winnings. In 2016 a Federal Judge ruled that Ivey and Cheung Yin Sun must repay US$10 million to the Borgata for violating New Jersey's Casino Controls Act, which prohibits marking cards.
Later in 2012 he was reported to have won £7.7 million (approx. $11 million) playing punto banco, a version of baccarat, at Crockfords casino in London. Crockfords refunded his £1 million stake and agreed to send him his winnings, but ultimately refused payment. Ivey sued them for payment, but lost in the UK High Court; it was judged that the edge sorting was "cheating for the purpose of civil law". It was accepted that Ivey and others genuinely considered that edge sorting was not cheating, and deemed immaterial that the casino could easily have protected itself. Critically, the judgment pointed out that Ivey had gained an advantage by actively using a croupier as his innocent agent, rather than taking advantage of an error or anomaly on the casino's part. Ivey appealed the judgement but he was unsuccessful.