Trial court errs by not applying independent review standard when ruling on Penal Code section 995 motion. Appellant was charged by complaint with possession of heroin for sale and other offenses. At the preliminary hearing the magistrate found the evidence insufficient to bind appellant over on possession for sale and held appellant to answer on simple possession. The prosecution filed an information which reinstated the possession for sale count (Pen. Code, § 739). Appellant moved to dismiss under section 995. The court, believing itself bound by the magistrate’s finding, granted the motion. The prosecution appealed. Held: Reversed. At the preliminary hearing, the prosecution’s expert opined the heroin was possessed for sale, based on the quantity possessed. The magistrate found the expert credible but that quantity alone was insufficient indicia of sales. In ruling on the section 995 motion the court did not find that the magistrate made factual findings, but felt it was bound by the magistrate’s sufficiency determination. When a defendant challenges a charge under section 995, the character of review depends on whether the magistrate made findings of fact. If so, those findings are conclusive if supported by substantial evidence. If not, a reviewing court cannot assume the magistrate resolved factual disputes or made credibility determinations; the matter is reviewed independently. On review by writ or appeal, the appellate court disregards the superior court’s ruling and reviews the magistrate’s holding order. Here, the superior court mistook the scope of its review because the magistrate did not make factual findings—thus, its holding was subject to independent review. There was no evidence offered to impeach the credibility of the prosecution expert, whose testimony was sufficient to support a probable cause finding on possession for sale.