The company maintained dossiers on card counters, serial jackpot winners, and other individuals, chiefly professional gamblers using legal techniques to gain an advantage in casino games; these profiles were regularly published in the Griffin Book, and distributed to subscribing casinos. Griffin Investigations was instrumental in ending the MIT Blackjack Team’s winning streak, after a Griffin investigator purchased the names, photographs, and other details identifying the group’s members and the company distributed the information to casinos. Roughly half of the major casinos in the U.S. once subscribed to Griffin’s services.
Griffin also marketed a controversial face recognition system that used computer software to compare gamblers' faces against several volumes of mug shots. According to a Las Vegas Sun article, Beverly Griffin, co-owner of Griffin Investigations, "estimates as many as half of Southern Nevada's casinos now use biometric technology to identify the faces of card cheats or other undesirables" However, a Las Vegas casino surveillance director (writing under the pseudonym Cellini) reported in the 2004 book The Card Counter's Guide to Casino Surveillance that biometric technology was considered virtually useless by actual casino surveillance operatives because of overwhelming numbers of false reads.