BY ELIZABETH ZAVALA Two Tarrant County men have pleaded guilty in federal court in two separate child pornography cases.John C. Pinkston, of Fort Worth, pleaded guilty Friday to one count of possession of child pornography, according to a news release from the U.S. Attorneys Office, Northern District of Texas. According to documents, Pinkston, 40, was arrested in May after he admitted to federal authorities executing a warrant at his home that he had child pornography on his computer.