Warning Signs When You Suspect Somebody Is Marking Cards at a Casino

Person Shuffling Cards and a Sharpie Marker

I’ve spent a fair amount of time handling playing cards as both a player and a dealer. And while my time behind the box eventually gave way to a career beating the house, I still utilize one aspect of my dealer training to this day—game security.

Whether in the poker room or the table game pit, a few unscrupulous players will always attempt to mark and track cards in hopes of gaining an edge. Card marking isn’t as prevalent as it once was, but it’s still a plague on the casino industry which should be snuffed out. To that end, here are five tips to help protect any game you’re sitting in from card marking cheats.

They’re Constantly Rubbing, Scratching, or Bending the Cards

The most primitive form of card marking in a casino is often performed inadvertently, as inexperienced players mishandle their cards. Gripping them too tightly, scratching them with a sharply manicured fingernail, or smudging them with dirty palms are all ways cards can be accidentally marked.

Casino dealers are trained to spot situations such as this, advising the player in question to avoid over handling while removing and replacing the marked card(s). And for the most part, once a player has been verbally warned, they’ll be extra careful to handle their cards with care going forward.

Person Holding Playing Cards

On the other hand, you’ll often see regulars and longtime players who can’t seem to keep their mitts off the merchandise. They’ll check and recheck their hole cards, nervously tap a finger on the card back, or “drop” a stack of chips in the center. In any event, a player continually reaching out to handle one’s cards—especially in between turns to act when others aren’t paying attention—is a good sign that something’s amiss.

A skilled card cheat only needs a second or two to identify and mark high-value cards like the 10s, royalty, and aces in blackjack. All it takes is a bit of pressure with a specially clipped and filed fingernail to leave a slight indentation in the card’s corner. After that, the marked card gets slipped back into the deck following the conclusion of the hand.

Once the cheat has marked as many high-value cards as they can, their real game begins in earnest, which brings us to the next major warning sign to watch for.

They Have Eyes on Everybody Else’s Cards and Not Their Own

For folks who employ the scratch or  indent method, simply loading up the deck with marked cards is only half the battle.

The cheater needs to spot their markings quickly and accurately, all while the hand is already underway. They accomplish this by essentially ignoring their own cards while the dealer is delivering around the table. Rather than peek down and squeeze the hole cards in their hand, marking specialists instead survey the table with a series of surreptitious glances.

Just picture a snake darting its eyes in every direction, and you’ll get the drift… Anytime you feel like a fellow player is looking at your cards or the dealer’s cards more than their own, your “Spidey sense” should be tingling. After all, this player has no legitimate reason to be staring at the back of your cards so intently.

And when you have a distinct lack of legitimate reasons, illegitimate reasons are the rational alternative. By now, you might be wondering how this information can be processed and acted upon in real time.

Marking a Casino Card

Well, in a traditional real money poker game, the slow pace of play ensures card markers have plenty of time to spot and interpret their markings. One player can take a minute or two to act on their hand, providing an ample window of opportunity for a cheat to size up the table and identify points of opportunity.

And if you’ve ever played no limit Texas Holdem before, just imagine the opportunities for profit which can arise by marking and spotting an opponent’s hole cards. You’ll always know when they “have it,” leading to easy folds and money saved. Conversely, you’ll always know when they’re bluffing, leading to snap calls and huge pots that you don’t really deserve.

As for the table games, the battle lies between player and dealer, which brings us to the third warning sign on our list…

They Only Gamble When Sitting Closest to the Dealer’s Shoe

Table games run at a much faster pace than traditional poker, so card markers must be prepared to spot their ill-gotten gains immediately.

To make that happen, experienced cheats will only play when sitting in the first chair to the left of the dealer. Also known as the “first base” box, this seat is located as close to the dealer’s shoe as you can get.

For casino table games, the card marker’s priority is to tag and spot the prioritized high-value cards that matter most in that particular game.

Baccarat cheats, for example, can gain an edge of 7% on the house by betting on the banker hand whenever the first card dealt is high (6, 7, 8, or 9).

At the blackjack table, simply marking the aces and 10-value cards is enough to completely flip the script on casino operators. Instead of facing a 0.50% house edge, players using basic strategy in conjunction with marked cards can “earn” an edge of 13% when they get a 10 to start the hand. That edge increases to a ludicrous 52% when an ace rolls off first, which is why blackjack is by far the most targeted table game for aspiring cheats.

If you’re enjoying Mississippi Stud Poker, marking just the Jacks and adjusting your play to capitalize accordingly creates a 38% edge for the player.

And in Three-Card Poker, marking the aces, kings, and queens produces a 16% edge for players who can spot the hidden royalty.

All things considered, you can see why so many gamblers take the ultimate risk by marking casino cards. But all of their “work” is rendered irrelevant if they’re sitting anywhere else but first base. Knowing that fact, combining the first two warning signs on this page with a habitual first base player likely means your game has a problem.

They Touch Their Lips and Leave Residue on the Casino Cards

Let’s face facts: Casino playing cards aren’t the cleanest surfaces on the planet.

With cigarette tar, sweat, sunscreen, and finger foods, gamblers tend to leave a little something behind after handling cards for an extended period. Fortunately, for you and I, the casinos take care to clean and/or replace their cards with regularity.

That only helps over the long-term, however, and a card marker who utilizes “daub” only needs a short session to score big wins. Daub is the technical term for a substance magicians and card cheats typically refer to as “invisible ink.” Whatever you call the stuff though, it can be rubbed onto the back of a card with just the flash of a finger, and nobody in the room but the cheat will know it.

Jacks Casino Playing Cards

Imagine how your fingers feel after rubbing a bit of Carmex or ChapStick on your dried lips. While your lips are now hydrated with a soothing balm, your fingertip probably feels greasy and gross. No matter, a simple wipe on your pantleg should do the trick… But not for a dauber.

These casino cheaters pretend to apply lip balm, but they’re really using specially designed ink that becomes invisible when it makes contact with the air. Transferring the daub from their lip to their fingertip to their card back can be done almost instantly, and the best cheats make it look perfectly natural.

They’re Wearing Eyeglasses With Special Tint or Sunglasses

This form of casino game deception requires a secondary tool to succeed—special eyewear designed to “see” invisible daub.

This eyewear can come in many forms, but the most common sights in Sin City security rooms are tinted eyeglasses or sunglasses. Of course, millions of gamblers visit Las Vegas wearing their glasses every year, so this tip alone isn’t enough to provide probable cause.

With that said, when you see a player with shiny fingers handling their cards constantly, while checking out your hand and sitting at first base to boot, you’re in trouble.

Quietly exit the game and inform the pit boss or manager immediately while avoiding any attention from the cheat. In the best-case scenario, you’ll help take them down with a minimum amount of drama.


Thanks to casino surveillance technology like the omnipresent “eye in the sky” cameras, casinos have never been a safer place to play. Gamblers today don’t have to worry about counterfeit chips or stacked decks, but card markers still rear their ugly head from time to time.

Just a few years ago, in fact, the World Series of Poker (WSOP) endured a suspected card marking scandal linked to defectively manufactured decks. Card marking cheats might be rare, but they’re still a threat to stay vigilant against. So, I hope these five warning signs serve you well on your next casino adventure.