Editing Card counting (section)

=== 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]].