There were no corroborating witnesses or hard evidence to back up Stempel's accusations, and Enright dismissed them as being rooted in jealousy over Van Doren's success. It took Ed Hilgemeier, a contestant-in-waiting who found a notebook full of answers belonging to Marie Winn, another contestant on the new quiz show "Dotto," airing on CBS, to convince authorities and the "Journal-American" that Stempel should be taken seriously. Manhattan Assistant District Attorney Joseph Stone, who directed two grand jury probes into the case, states that Enright described Stempel to him as "a disturbed person and a blackmailer" and denied ever giving Stempel advance questions and answers. Three days after "Twenty-One" contestant Richard Jackman, a writer from Oneonta, New York, told Stone that he, too, had been coached in advance of his appearance on October 3, "Twenty-One" was canceled. The investigation of the quiz show scandal then began in earnest. Jackman only realized the game was fixed the night he appeared, when the questions he was asked were identical to the ones Enright had reviewed with him in a "practice session" that afternoon. Enright quickly countered, denying any wrongdoing or fraud had taken place, suing the "Journal-American", and mounting a campaign to discredit Stempel. At a sensational press conference, he attempted to demonstrate that Stempel was mentally unstable by playing a recording of a conversation with him that Enright had secretly taped. To further discredit him, Enright also produced the statement that Stempel had signed earlier, declaring that "Twenty-One" was an honest program, that Barry and Enright were beyond reproach, and that no rigging had taken place. Jack O'Brian felt there was an "undercurrent" of coercion going on. Not only did some of the producers lie to the grand jury, they also had urged contestants to perjure themselves. In lower Manhattan, the grand jury was convened for nine months and heard testimony from more than 150 contestants. It is estimated that more than 100 lied under oath. Stempel continued telling the truth to anyone who would listen, but it was his unsubstantiated word against everyone else's; there was still no hard corroborating evidence. His testimony to the DA and the grand jury implicated Van Doren in the fraud, but there was massive resistance in accepting this accusation. Suddenly, to everyone's astonishment, the grand jury testimony was sealed from the public by Judge Mitchell Schweitzer, for reasons that to this day are still not clear.