They used an unnatural setup, themselves.
(This 1937 dice optical illusion was
a giveaway for a liquor mixer.)
The Wynn Las Vegas casino filed a lawsuit against two of their customers, Leonardo Fernandez and Veronica Dabul, for cheating by engaging in "dice sliding". The casino wants them to return $700,000 they won while playing craps.
What is "dice sliding?" That's when gamblers slide dice across a gaming table so they can control which side of the die lands face up. It's a pretty obvious move when done on its own, so gambling cheats usually work in teams, where some team members distract or hide the actual fake roll from the dealer.
Real or valid dice rolls require the dice to roll on the table, then bounce in the air and off the table's back wall.
Dice "sliders" or "scooters" may not always be able to accurately control all their rolls, but they can improve their odds a bit by having one die tumble and one die slide.
The two players were caught after one night after winning $145,000 with seven rolls, which alerted the casino that something was wrong.
Here's a video showing a dice sliding technique:
Dice Sliding with Bill Zender
Couple accused of dice sliding at Wynn Las Vegas, Las Vegas Review Journal>>