Playing cards lead to tips in cold cases:

Special Agent Tommy Ray, a state law officer in Polk County, Fla. [...] made his own deck of cards, each bearing information about a different local criminal case that had gone cold. He distributed the decks in the Polk County jail. His hunch was that prisoners would gossip about the cases during card games, and somehow clues or breaks would emerge and make their way to the authorities. The plan worked. Two months in, as a result of a tip from a card-playing informant, two men were charged with a 2004 murder in a case that had gone cold.

Just needs a prison related pun based around Texas Hold ‘em…