How have courts interpreted "careful scrutiny" in a preliminary hearing where a defendant is denied the right to cross-examine witnesses?

15 For instance, in Mills v. Superior Court, supra, 42 Cal.3d 951, 957, 232 Cal.Rptr. 141, 728 P.2d 211, this court determined that it must "subject to careful scrutiny any legislation restricting the ability of defendants to cross-examine witnesses whose testimony is offered as evidence of probable cause [at a preliminary hearing]." Even when applying "careful scrutiny," however, this court stated: "At the same time, we are mindful that it is our duty to uphold a statute unless its unconstitutionality clearly, positively, and unmistakably appears; all presumptions and intendments favor its validity. [Citations.]" (Ibid.)