David Durk, the New York police detective who teamed up with officer Frank Serpico to breach the aptly named 'blue wall of silence' died yesterday. His testimony before the Knapp Commission investigation into police corruption in 1971 made for some of the most moving public testimony ever broadcast.  Writing in The New York Times Book Review, WNYC Director Mary Perot Nichols said it was largely thanks to Durk's persistence and contacts that their campaign against police corruption became a matter of public record. Above is an excerpt from his remarks on December 21, 1971.