Detecting a biased deck in blackjack involves carefully observing the game for any irregularities in card distribution, dealer behavior, or shuffling. If certain cards seem to appear more frequently than expected, or if card sequences appear in a predictable pattern, it might suggest a deck bias. A worn or damaged deck could also cause this, with specific cards showing signs of wear that make them easier to identify. Inconsistent shuffling or the dealer favoring certain hands could also be clues. Additionally, tracking your betting outcomes and comparing them to normal probabilities can help spot unusual patterns. If you notice any of these signs, it may indicate a biased deck, and the casino should be notified to address the issue.