RAPID CITY, SD (KELO) -- A former treasurer of the Oglala Sioux Tribe pleaded not guilty to theft charges in federal court Friday. A grand jury indicted 50-year-old Mason Big Crow for larceny, embezzlement and theft from an Indian Tribal Organization. Prosecutors say Big Crow embezzled tribal funds to make personal purchases that had not been authorized by the tribe and that were used for his personal benefit. Prosecutors say as tribal treasurer, Big Crow had nearly exclusive access to the tribe's debit and credit card.