Biased Roulette Wheel

For casino owners, roulette should theoretically be a sure thing. Over time the house edge will show and a roulette wheel will produce a steady stream of profits for as long as a casino remains open. Individual players may win, but overall the casino should come out ahead.

However, this idea goes out the window the moment a casino has a biased roulette wheel. Over the last two centuries there have been many instances in which a biased roulette wheel has been found and exploited by smart players, allowing them to beat the house and score huge profits over the course of days, weeks, or longer periods of time. While most casinos now use wheels that give fair results day-in and day-out, just one biased wheel can open the door and allow players to break the bank.

What is a Biased Roulette Wheel?

Biased Roulette Wheel

“Biased roulette wheel” is a term identifying any wheel that gives results that are different than those expected by chance. There are two ways this might occur, either the casino can rig a wheel to give non-random results or a wheel can have imperfections that lead to biased results.

Rigged wheels are not common now, but were a mainstay of underground casinos through much of the first half of the 20th century. Operators would use these wheels to rip off customers and take more than their fair share of large bets. Of course, this practice was dangerous as customers who found out about these wheels would naturally be angry about not receiving a fair shake. Since roulette tables are naturally profitable even without any rigging, even the majority of unregulated casinos eventually decided that such wheels simply weren’t worth the risk.

When most people talk about biased roulette wheels, they’re talking about the unintentionally biased wheels that catch casinos by surprise. Roulette wheels are complex and any small amount of unbalancing can subtly influence results so that certain sections of the wheel are more likely to win than others. Given that the house edge for the casino in roulette isn’t overwhelming, even a small bias can sometimes be enough for players to suddenly have the edge – if they know where to place their bets.

Examples of Biased Roulette Wheels

Joseph Jagger Roulette

There have been several high-profile instances in which players have taken advantage of biased roulette wheels in casinos around the world. Perhaps the first – and still most famous – example of a player winning big by analyzing the results of a roulette wheel came in 1873, when Joseph Jagger managed to win about £65,000 from the Beaux-Arts Casino in Monte Carlo. By using six clerks to record the results from all six roulette wheels at the casino, Jagger found out that one of the wheels showed a clear bias toward a group of nine numbers grouped together on the wheel. The casino fought back by moving around the wheels and sometimes forced Jagger into heavy losses. However, in the end, Jagger still won the equivalent of over £3 million in modern terms (when adjusted for inflation).

A more recent example took place in the 1990s, when Gonzalo Garcia-Pelayo took on similar efforts to track the results of roulette wheels at the Casino de Madrid. Eventually, Garcia-Pelayo was able to find a wheel that had a bias and he ultimately won over one million euros over the course of several days. When the casino figured out what he was doing they made an attempt to take legal action, however the courts ruled against the casino, finding that Garcia-Pelayo did nothing wrong. They decided that the casino was at fault for not maintaining their roulette wheels.

Exploiting a Biased Roulette Wheel

Properly exploiting a biased roulette wheel is a difficult task. If a player believes that a wheel may be biased, they must first track numbers at the table in order to gain mathematical proof that this is occurring. This isn’t terribly difficult as players routinely track numbers, so it isn’t likely to draw suspicion if you do so, even over a long period of time.

Unless a wheel is showing a horrible bias – in which case the casino is likely to notice, too – it’s likely that you’ll need at least several thousand spins before you can claim to be certain that a wheel really is biased. However, if there’s virtually any bias in a wheel at all, that may be enough to make playing that roulette wheel profitable.

On a European roulette wheel each number should win approximately 2.70% of the time. If you can be certain that a number will instead win only slightly more often – say 3% of the time – that is enough to make the wheel profitable. Playing that number every time would result in a player edge of 8%, which is more than enough to exploit a casino for millions of dollars – provided they don’t notice the bias before you win big.

Read here for a fully dedicated article to Beating Roulette When a Wheel Bias Occurs by Al Moe.