Who makes the detrmination that probable cause exists before conducting a warrentless search of vehicles?
The officer that makes the decision and conducts the search must be able to justify the search, by articulating his reason for doing so. Therefore, the searching officer makes the determination that the necessary cause exists to justify the search. If his on-the-scene determination is not sufficient or ruled invalid, the evidence found will be ruled inadmissable, and the case might be lost.