What is the test for a motion to suppress evidence under section 1538.5 of the California Criminal Code?

A defendant may move to suppress evidence under section 1538.5 on grounds that a search without a warrant was unreasonable. A warrantless search is presumptively unreasonable, and the prosecution bears the burden of demonstrating a legal justification for the search. (People v. Redd (2010) 48 Cal.4th 691, 719, 108 Cal.Rptr.3d 192, 229 P.3d 101.) In reviewing a trial court's ruling on a motion to suppress, we defer to the trial court's factual findings, express or implied, where supported by substantial evidence. (Ibid. ) And in determining whether, on the facts so found, the search was reasonable for purposes of the Fourth Amendment to the United States Constitution, we exercise our independent judgment. (Ibid. )