What is the test for a motion to suppress evidence from a traffic stop?

Our review of a trial court's ruling on a motion to suppress the evidence from such a stop is well established. A warrantless search is presumed to be unreasonable, and the prosecution bears the burden of demonstrating a legal justification for the search.... We defer to the trial court's factual findings, express or implied, where supported by substantial evidence. In determining whether, on the facts so found, the search or seizure was reasonable under the Fourth Amendment, we exercise our independent judgment. (People v. Redd (2010) 48 Cal.4th 691, 719, 108 Cal.Rptr.3d 192, 229 P.3d 101.)