When a defendant objects to introduction of a confession and claims a waiver of constitutional rights was invalid, the judicial officer to whom the objection is made must determine whether the People have proven by a preponderance of the evidence that the defendant's waiver was indeed voluntary and knowing. ( People v. Markham (1989) 49 Cal. 3d 63 [260 Cal. Rptr. 273, 775 P.2d 1042]; Colorado v. Connelly (1986) 479 U.S. 157 [107 S. Ct. 515, 93 L. Ed. 2d 473] [93 L. Ed. 2d 473].) This standard applies whether it is a magistrate or a superior court judge conducting the suppression hearing. Both must determine whether the confession is legal and admissible. That a magistrate ultimately determines the existence or absence of probable cause has no relationship to the standard by which the magistrate determines the validity of a waiver of Miranda rights and the admissibility of a confession. Furthermore, within the framework of determining probable cause, "the magistrate may weigh the evidence, resolve conflicts, and give or withhold credence to particular witnesses. In other words, in assisting him in his determination of 'sufficient cause,' the magistrate is entitled to perform adjudicatory functions akin to the functions of a trial judge." (People v. Uhlemann (1973) 9 Cal. 3d 662, 667 [108 Cal. Rptr. 657, 511 P.2d 609].) Indeed, it is error for a magistrate not to allow a defendant to put on evidence at the preliminary hearing regarding the validity of confessions. ( People v. Neal (1942) 53 Cal. App. 2d 379, 381, 383 [127 P.2d 996].)