Warren gained a statewide reputation as a tough, no-nonsense district attorney who fought corruption in government and ran his office in a nonpartisan manner. Warren strongly supported the autonomy of law enforcement agencies, but also believed that police and prosecutors had to act fairly. Unlike many other local law enforcement officials in the 1920s, Warren vigorously enforced Prohibition. In 1927, he launched a corruption investigation against Sheriff Burton Becker. After a trial that some in the press described as "the most sweeping exposé of graft in the history of the country," Warren won a conviction against Becker in 1930. When one of his own undercover agents admitted that he had perjured himself in order to win convictions in bootleg cases, Warren personally took charge of prosecuting the agent. Warren's efforts gained him national attention; a 1931 nationwide poll of law enforcement officials found that Warren was "the most intelligent and politically independent district attorney in the United States".