How Does a Casino Know When a Player is Cheating?

Hand Hiding Ace of Diamonds Card Inside Sleeve, Cheating Cross Out
If you’ve ever watched Ocean’s Eleven and its sequels, you probably found yourself wondering how realistic their portrayals of casino security are. I love the sequence in the first movie where Elliott Gould runs through a list of failed heists.

Where does the line really fall between what casinos know and what the movies pretend they know?

Well, it helps to think about the years in which the movies were made. Casino security can now do many things that were once fantastic or considered impossible. Facial recognition technology is being deployed in casinos, airports, and ports of entry around the world.

Until about 10 years ago facial recognition technology was an idea straight out of science fiction.

The math required to recognize faces and look them up in a database is very complicated. You need a lot of computer power to execute that task.

The other big movie gimmick is the super computer sitting in a cold room somewhere, calculating the probabilities faster than humans can think of the possibilities. That trope is still a few years away. But computers crunch a lot of numbers for casinos these days.

What is the secret to casino security?

How do these companies prevent clever criminals from constantly ripping them off?

The answer is a mix of different strategies.

First Line of Defense is Casino Staff

You have the dealers and the technicians working the floor. They are trained to look for suspicious behavior. They’ll report it to a supervisor rather than confront you.

Row of Slot Machines in Casino, Man in Suit Looking Through Magnifying Glass

And you have the security teams. These may be armed guards standing visibly on the floor or they may be people watching an array of video monitors in a back room.

If someone walks up to the cashier window and pulls a gun on them I’m sure the staff are trained not to worry about the money. Their job is stay calm and let someone else handle the problem.

But robbing a casino isn’t really cheating. Cheaters are more likely to steal other players’ chips or tickets, do something tricky with the cards, or attach devices to slot machine games.

The floor staff’s role in security is to report anything suspicious to a supervisor or security. They are an intelligence network.

Think of spy movies where field operatives as the local market vendors if they see anything out of the ordinary.

The larger casinos sometimes open up to the media about how they manage security. They send their personnel to training. They share information with each other.

Many casinos hire experienced security consultants who come in and teach seminars about how players cheat. They also provide input on security procedures and systems.

Law enforcement works with the casino industry too. In some jurisdictions they have a very heavy investment in catching criminals and organized cheating rings.

Video Monitoring Is the Second Line of Defense

Players most likely to be caught cheating are blackjack card counters. Most people who count cards are inexperienced.

You need 3 skills to successfully count cards in blackjack:

  1. A basic but thorough knowledge of the game
  2. The ability to keep track of the cards played in-between shuffles
  3. Good acting ability

Security Camera, Recording IconSecurity experts who talk about how card counters are caught say they know the counters usually work in teams. They need to be aware of what everyone else is dealt. Card counters must pay closer attention to other players’ cards than non-counters.

If the counters are good actors they’ll be harder to spot. But what they cannot change so easily is their appearance. That is why real card counters often resort to disguises.

The people monitoring the videos look for signs you’re in disguise. They may be better at recognizing wigs and extensions than the average person.

But though card counters are fairly easy to spot casinos must fall back on other methods to spot people who cheat in other games.

Casinos Need More Time to Spot Large Cheating Rings

Organized cheaters have figured out that statistics and probability factor into every casino’s operations. Computer systems are now affordable for virtually every casino in operation. All casinos have to do is lease the software and install it on a few computers.

The cheaters respond by bringing more people into play.

One ring of cheaters who swapped chips at roulette tables operated for months before they were caught. Dozens of arrests finally put an end to their scheme.

Eastern European criminals acquired older slot machines and reverse-engineered their random number generators. Then they bought a cheap supercomputer and used it to process real-time images of slot machine games.

The slot machine game players were sent out to casinos across the world. It took a while for casinos to understand they weren’t just facing people. They were being outwitted by a computer.

How Casinos Use Math to Catch Cheating

If the dealers and pit bosses don’t see you successfully counting cards, and if the video room guys miss all the cues, there is another way they’ll catch you.

They analyze every game and table’s results. These results are compared to past months’ performance.

Allowing for variations in all aspects of game play, these statistical systems compare their performance data against models. Those models were developed by experts in math and statistics using a lot of data.

Casino Security on Radio, Woman Holding Up Money in Casino

A statistical model tells a casino what normally happens. Every now and then someone pushes the results outside the model’s expected limits. Anomalies do happen but the casino might flag a player for further scrutiny.

Player club cards make it easier to track a player’s success and failures. Some players are luckier than others and they’ll win a bit more than usual. The statistical models expect that.

If a player wins consistently over an extended period of time – say, a 3 days in a row – that’s a bit too unusual. The casino will sit up and take notice.

Repeat cheaters, especially on slot and video card games, try to be clever. They’ll spread their cheating out across several casinos or they’ll play different games. And yet it seems even the most clever cheaters leave footprints for the data sleuths to follow.

The problem for every cheater is that casinos know what normal gameplay looks like. The statistics don’t change much over time because millions of people gamble all across the world, all year long.

Most of those people are not cheating so their gameplay data creates what is normal.

Cheaters create data patterns that look like tiny blips on a radar screen. They are pebbles dropping into otherwise still ponds.

Why Do Cheaters Eventually Get Caught?

There is an old adage that says a criminal always returns to the scene of the crime. If you cheat once and don’t get caught, all you need to do to get away with it completely is never cheat again.

People who intend to cheat want an advantage over the casino – so they think to themselves why cheat only once?

Casino Table Game with Poker Chips Stacked, Man Getting Arrested by Two Cops

And that is what eventually leads to cheaters being caught. They go back and cheat again. And then they cheat again.

A famous case involved 2 men who discovered a flaw in a video poker game. They learned by accident that if they played a certain sequence the game would pay them a big prize.

Their cheating began unraveling when they went back to the same casinos and used the same cheat over and over again. Their many wins added up to an unusual pattern.

The guys thought they could keep walking out with a few thousand dollars each time, but they didn’t realize that this isn’t a normal pattern. No one wins that often without cheating.

Maybe if they had only cheated once at each casino, and traveled around the country or world playing at every casino only once, they might have gotten away with the scheme.

But they went back to the same casinos until one of them was caught. And then he talked.


The casino only has to catch one person cheating. Once they identify one member of an organized cheating ring they just need to wait.

Time is always on the casino’s side. Although casinos say they let a lot of small cheating slide, they have to be careful about letting too much pass under their noses.

As cheaters become overconfident they slip up. Once a casino has a reason to believe that repeat or systematic cheating is in play they ramp up their resources and start looking for more clues.

Cheaters eventually cheat themselves by allowing greed to control their thinking. As long as they believe they are getting away with it cheaters will keep cheating in the same way over and over.

And that creates a pattern that looks very different from normal game play. It’s a pattern casino security eventually sees and responds to. Many people learned that lesson the hard way.