In 1970, New York City organized the Knapp Commission to hold hearings on the extent of corruption in the city's police department. Police officer Frank Serpico's startling testimony against fellow officers not only revealed systemic corruption but highlighted a longstanding obstacle to investigating these abuses: the fraternal understanding among police officers known variously as "the Code of Silence" and "the Blue Curtain" under which officers regard testimony against a fellow officer as betrayal. In 1991, the Christopher Commission was formed in Los Angeles in response to the beating of Rodney King in March of that year by four members of the Los Angeles Police Department. In 1992, the Mollen Commission, commissioned to investigate reports of police corruption in New York City, noted that "The pervasiveness of the code of silence is itself alarming." One New York City police officer said, "If a cop decided to tell on me, his career's ruined...He's going to be labeled as a rat." The following year saw the founding of the Civilian Complaint Review Board, an all-civilian board tasked with investigating civil complaints about alleged misconduct on the part of the New York City Police Department.