What is the test for admissible evidence in a murder trial?

"All relevant evidence is admissible" (Evid.Code, 351) but not all admissible evidence need be offered. A jailhouse informant may claim the defendant confessed but only a gullible prosecutor would automatically offer such suspect testimony. The testimony of a racist police officer may harm the prosecution more than the defense. As one court observed: "during the trial process, things change and the best laid strategies and expectations may quickly become inappropriate: witnesses who have been interviewed vacillate or change their statements; events that did not loom large prospectively may become a focal point in reality. Thus, there must be some flexibility.... After hearing a witness, the necessity of a rebuttal witness may become more important." (People v. Hammond (1994) 22 Cal.App.4th 1611, 1624, 28 Cal.Rptr.2d 180.)