What is the test for obtaining access to unprivileged evidence in a criminal case?

" 'A showing . . . that defendant cannot readily obtain the information through his own efforts will ordinarily entitle him to pretrial knowledge of any unprivileged evidence, or information that might lead to the discovery of evidence, if it appears reasonable that such knowledge will assist him in preparing for his defense.' " (Lemelle v. Superior Court, 77 Cal.App.3d 148, at 162, 143 Cal.Rptr. 450, at 459.) Although the defendant need not demonstrate that the evidence he seeks would be admissible at trial, he must make a showing that the requested information will facilitate ascertainment of the facts and a fair trial.