Question: The Commission to Investigate Alleged Police Corruption (known informally as the Knapp Commission) became informed of Frank Serpico's police corruption by him doing what?
Sentence (from "Clemence B. Horrall"): Horrall had become chief when Hohmann, under pressure from Los Angeles Mayor Fletcher Bowron, voluntarily took a demotion to deputy chief after he had become ensnared in a police corruption trial that had embarrassed the mayor.
Relevant evidence: No