What is the test for discovery of a law enforcement officer personnel file?

A criminal defendant has a limited right to discovery of law enforcement officer personnel records. (Pitchess, supra, 11 Cal.3d at pp. 537-538; Evid. Code, 1043-1045.) "To initiate discovery, the defendant must file a motion supported by affidavits showing 'good cause for the discovery,' first by demonstrating the materiality of the information to the pending litigation, and second by 'stating upon reasonable belief' that the police agency has the records or information at issue. [Citation.] This two-part showing of good cause is a 'relatively low threshold for discovery.' [Citation.]" (Warrick v. Superior Court (2005) 35 Cal.4th 1011, 1019 (Warrick).)