In 1970, Charles was encouraged to run for the Tennessee Court of Criminal Appeals. The opening was for the Eastern Division, but it was a statewide race. "It was a very dull race," Anna Belle commented. "A judicial candidate can't promise a thing."
She recounted an interesting story that came out of the race. They were campaigning in a big city and went to the courthouse. There they found cards for all candidates — except Charles. After looking around he found his cards — in a wastebasket. Despite this minor setback, Charles won the Eastern Division seat.
When the entire court, consisting of eight or nine members, met, it was in Jackson for the Western Division, Nashville for the Middle Division and Knoxville for the Eastern Division. Anna Belle remembers this interesting story associated with one meeting. Charles had been on the court for only a short while when a friend in Jackson invited the entire court and their families to a reception honoring Charles. After the reception, a judge from East Tennessee went home and told his wife he believed he would like the O'Briens. He told her a friend of the O'Briens had the reception in her home and he had such a good time. "How nice it was to use the O'Briens' anniversary as the reason to have a dinner and invite the whole court," he said. His wife, however, didn't seem too interested, according to Anna Belle. This prompted the man to ask, "Did you hear what I said?" The wife said, curtly, "Yes, I heard what you said. It was your anniversary, too." Anna Belle says more than likely he never forgot it again.
After winning the Eastern Division seat in 1970, Charles served for 17 years. In 1987 he was appointed to the Tennessee Supreme Court and was later named chief justice.