Editing Card counting (section)

== Casino reactions ==
=== Detection ===

Monitoring player behavior to assist with detecting the card counters falls into the hands of the on-floor casino personnel ("[[pit manager|pit bosses]]") and casino-surveillance personnel, who may use video surveillance ("the [[eye in the sky (camera)|eye in the sky]]") as well as computer analysis, to try to spot playing behavior indicative of card counting. Early counter-strategies featured the dealers learning to count the cards themselves to recognize the patterns in the players. Many casino chains keep databases of players that they consider undesirable. Casinos can also subscribe to databases of advantage players offered by agencies like [[Griffin Investigations]], Biometrica, and OSN (Oregon Surveillance Network).<ref name="blue2">{{cite book |last1=Blaine |first1=Rick |title=Blackjack Blueprint: How to Play Like a Pro ... Part-Time |date=May 2014 |publisher=Huntington Press |isbn=978-1935396536}}</ref> Griffin Investigations filed for [[Chapter 11]] bankruptcy protection in 2005 after losing a libel lawsuit filed by professional gamblers.<ref>{{cite web |author=Liz Benston |title=Griffin book producer files for Chapter 11, citing suit |date=13 September 2005 |url=https://lasvegassun.com/news/2005/sep/13/griffin-book-producer-files-for-chapter-11-citing-/ |access-date=15 June 2010 |publisher=LasVegasSun |archive-date=8 June 2010 |archive-url=https://web.archive.org/web/20100608063853/http://www.lasvegassun.com/news/2005/sep/13/griffin-book-producer-files-for-chapter-11-citing-/ |url-status=live }}</ref> In 2008 all Chapter 11 payments were said to be up to date and all requirements met, and information was being supplied using [[data encryption]] and [[secure server]]s.<ref>{{cite web |title=Minutes of the Private Investigators Licensing Board for 18 June 2008 |url=https://nevadapilb.glsuite.us/Clients/NVPI/Public/Documents%5CMinutes%5C2008-06-18.pdf |access-date=22 March 2018 |website=glsuite.us |archive-date=18 November 2017 |archive-url=https://web.archive.org/web/20171118223508/https://nevadapilb.glsuite.us/Clients/NVPI/Public/Documents%5CMinutes%5C2008-06-18.pdf |url-status=live }}</ref>{{vague|date=August 2019}} If a player is found to be in such a database, they will almost certainly be stopped from play and asked to leave regardless of their table play. For successful card counters, therefore, skill at "cover" behavior, to hide counting and avoid "drawing heat" and possibly being barred, may be just as important as playing skill.{{Original research inline|date=September 2021}}

Detection of card counters will be confirmed after a player is first suspected of counting cards; when seeking card counters, casino employees, whatever their position, could be alerted by many things that are most common when related to card counting but not common for other players. These include:<ref>{{cite book |last1=Zender |first1=Bill |title=Casino-ology 2: New Strategies for Managing Casino Games |date=April 2011 |publisher=Huntington Press |isbn=9781935396284}}</ref><ref name="James2">{{cite book |last1=Grosjean |first1=James |title=Exhibit CAA: beyond counting |date=2007 |publisher=South Side Advantage Press, LLC |isbn=978-0-9790061-4-2 |edition=1st |location=Las Vegas, NV}}</ref><ref>{{cite book |last1=Cellini |first1=D.V. |title=The card counter's guide to casino surveillance |date=2003 |publisher=Huntington Press}}</ref>
* Large [[buying in (poker)|buy-ins]].
* Dramatic bet variation especially with larger bets being placed only at the end of a [[shoe (cards)|shoe]].
* Playing only a small number of hands during a shoe.
* Refusal to play rated.
* Table hopping.
* Playing multiple hands.
* Lifetime winnings.

Card counters may make unique playing strategy deviations not normally used by non-counters. Plays such as splitting tens, doubling soft 18/19/20, standing on 15/16, and surrendering on 14, when basic strategy says otherwise, may be a sign of a card counter.

Extremely aggressive plays such as splitting tens and doubling soft 19 and 20 are often called out to the pit to notify them because they are telltale signs of not only card counters but [[hole carding]].

=== Technology for detecting card counters ===
Several semi-automated systems have been designed to aid the detection of card counters. The [[MindPlay]] system (now discontinued) scanned card values as the cards were dealt. The [[Shuffle Master]] Intelligent Shoe system also scans card values as cards exit the shoe. Software called Bloodhound and Protec 21<ref>{{cite web |title=Digitace Website |url=http://www.digitace.com |access-date=20 March 2009 |publisher=digitace.com |archive-date=15 January 2009 |archive-url=https://web.archive.org/web/20090115004810/http://www.digitace.com/ |url-status=live }}</ref> allows voice input of card and bet values, in an attempt to determine the player edge. A more recent innovation is the use of [[RFID]] signatures embedded within the casino chips so that the table can automatically track bet amounts.<ref>{{cite web |last=Gilbert |first=Alorie |title=CNET News story, "Vegas Casino Bets on RFID" |url=https://www.cnet.com/tech/services-and-software/vegas-casino-bets-on-rfid/ |access-date=20 March 2009 |publisher=News.com.com |archive-date=26 August 2021 |archive-url=https://web.archive.org/web/20210826230340/https://www.cnet.com/tech/services-and-software/vegas-casino-bets-on-rfid/ |url-status=live }}</ref>

Automated card-reading technology has known abuse potential in that it can be used to simplify the practice of ''preferential shuffling –'' having the dealer reshuffle the cards whenever the odds favor the players. To comply with licensing regulations, some blackjack protection systems have been designed to delay access to real-time data on the remaining cards in the shoe.<ref>{{cite web |title=High-Tech Casino Advantage Play: Legislative Approaches to the Threat of Predictive Devices |url=https://core.ac.uk/download/pdf/10678382.pdf |access-date=19 November 2017 |website=Core |archive-date=8 November 2017 |archive-url=https://web.archive.org/web/20171108080515/https://core.ac.uk/download/pdf/10678382.pdf |url-status=live }}</ref> Other vendors consider real-time notification to surveillance that a shoe is "hot" to be an important product feature.<ref>Aventura Technologies, [http://www.ati247.com/pdf/Real-Time%20Casino%20Solution_v01.2.pdf Real Time Casino Solution (PDF)] {{Webarchive|url=https://web.archive.org/web/20070306161251/http://www.ati247.com/pdf/Real-Time%20Casino%20Solution_v01.2.pdf |date=2007-03-06 }}, diagram 12, "Advantaged Play Server"</ref>

With card values, play decisions, and bet decisions conveniently accessible, the casino can analyze bet variation, play accuracy, and play variation.

''Bet variation''. The simplest way a card counter makes money is to bet more when they have an edge. While playing back the tapes of a recent session of play, the software can generate a scatter plot of the amount bet versus the count at the time the bet was made and find the trendline that best fits the scattered points. If the player is not counting cards, there will be no trend; their bet variation and the count variation will not consistently correlate. If the player is counting and varying bets according to the count, there will be a trend whose slope reflects the player's average edge from this technique.<ref>Arnold Snyder's ''[[Blackjack Forum]]'' periodical featured a printout that demonstrated this feature</ref>

''Play variation''. When card counters vary from basic strategy, they do so in response to the count, to gain an additional edge. The software can verify whether there is a pattern to play variation. Of particular interest is whether the player sometimes (when the count is positive) takes insurance and stands on 16 versus a dealer 10, but plays differently when the count is negative.

=== Countermeasures ===
Casinos have spent a great amount of effort and money in trying to thwart card counters. Countermeasures used to prevent card counters from profiting at blackjack include:<ref>{{cite book |last1=Nersesian |first1=Bob |title=The Law for Gamblers: A Legal Guide to the Casino Environment |date=May 2016 |publisher=Huntington Press |isbn=978-1935396628}}</ref><ref>{{cite book |last1=Zender |first1=Bill |title=Casino-ology: The Art of Managing Casino Games |date=October 2013 |publisher=Huntington Press |isbn=978-0-929712-56-7}}</ref><ref name="blue2" /><ref name="bjlaw2">{{cite book |last1=Rose |first1=I. Nelson |title=Blackjack and the law |last2=Loeb |first2=Robert A. |date=1998 |publisher=RGE Pub. |isbn=978-0910575089 |edition=1st |location=Oakland, CA}}</ref>
* Decreasing penetration, the number of cards dealt before a shuffle. This reduces the advantage of card counting.
* Banning known counters from playing blackjack, all games, or entering casino property (trespassing).
* Shuffling when a player increases their wager or when the casino feels the remaining cards are advantageous to the player (preferential shuffling).
* Changing rules for splitting, doubling down, or playing multiple hands. This also includes changing a table's stakes.
* Not allowing entry into a game until a shuffle occurs (no mid-shoe entry).
* Flat betting a player or making it so they cannot change the amount they bet during a shoe.
* Canceling comps earned by counters.
* Confiscation of chips.
* [[False imprisonment|Detention]] (back rooming).

Some jurisdictions (e.g. [[Nevada]]) have few legal restrictions placed on these countermeasures. Other jurisdictions such as [[New Jersey]] limit the countermeasures a casino can take against skilled players.<ref>{{cite web |last1=Rose |first1=I. Nelson |title=Dealing With Card-Counters – Gambling and the Law® |url=https://www.gamblingandthelaw.com/column/dealing-with-card-counters/ |access-date=17 November 2017 |website=www.gamblingandthelaw.com |date=27 June 2017 |archive-date=10 July 2018 |archive-url=https://web.archive.org/web/20180710010333/http://www.gamblingandthelaw.com/column/dealing-with-card-counters/ |url-status=live }}</ref>

Some countermeasures result in disadvantages for the casino. Frequent or complex shuffling, for example, reduces the amount of playing time and consequently the house winnings.<ref>{{cite web |last1=Zender |first1=Bill |title=TABLE GAME MANAGEMENT FOR THE SMALL CASINO, PART 2 |url=http://www.billzender.com/os/resources/media/table_game_mgmt_for_small_casinos_part_2.pdf |access-date=18 November 2017 |website=billzender.com |archive-date=22 April 2014 |archive-url=https://web.archive.org/web/20140422195308/http://www.billzender.com/os/resources/media/table_game_mgmt_for_small_casinos_part_2.pdf |url-status=live }}</ref><ref>{{cite web |last1=Zender |first1=Bill |title=TABLE GAME MYTHS PERSIST AMONG PLAYERS AND DEALERS |url=http://www.billzender.com/os/resources/media/Table-Game-Myths-Persist-Among-Players-and-Dealers-08-2014.pdf |access-date=18 November 2017 |website=billzender.com |archive-date=27 August 2016 |archive-url=https://web.archive.org/web/20160827103359/http://billzender.com/os/resources/media/Table-Game-Myths-Persist-Among-Players-and-Dealers-08-2014.pdf |url-status=live }}</ref> Some casinos use automatic shuffling machines to counter the loss of time, with some models of machines shuffling one set of cards while another is in play. Others, known as continuous shuffle machines (CSMs), allow the dealer to simply return used cards to a single shoe to allow playing with no interruption. Because CSMs essentially force minimal penetration, they greatly reduce the advantage of traditional counting techniques.<ref>{{cite web |last1=Barker |first1=Jeff |title=Horseshoe adds continuous shuffle machines, stirring industry debate |url=https://www.baltimoresun.com/business/bs-bz-casino-card-shufflers-20160711-story.html |access-date=18 November 2017 |website=baltimoresun.com |date=11 July 2016 |archive-date=19 November 2017 |archive-url=https://web.archive.org/web/20171119124049/http://www.baltimoresun.com/business/bs-bz-casino-card-shufflers-20160711-story.html |url-status=live }}</ref> In most online casinos the deck is shuffled at the start of each new round, ensuring the house always has the advantage.