An opinion was just released by the 9th Court of Appeals in Texas that explains when an officer may search your vehicle and why in Texas.
Here is the applicable discussion
Pursuant to the Fourth Amendment, a warrantless search is per se unreasonable unless it falls within an exception to the requirement for a warrant. Arizona v. Gant , 556 U.S. 332, 338 (2009); McGee v. State, 105 S.W.3d 609, 615 (Tex. Crim. App. 2003). The “automobile exception” allows for the warrantless search of a vehicle “if it is readily mobile and there is probable cause to believe that it contains contraband.” see Marcopoulos v. State, 538 S.W.3d 596, 599 (Tex. Crim. App. 2017); Keehn v. State , 279 S.W.3d 330, 335 (Tex. Crim. App. 2009); see also United States v. Ross, 456 U.S. 798, 825 (1982) (police may search a vehicle if they have probable cause to believe it contains evidence of a crime)...See California v. Carney, 471 U.S. 386, 391-92 (1985)(explaining that the “automobile exception” to the requirement of a warrant applies when a vehicle is being used on the highways). Probable cause exists when “the facts and circumstances within the knowledge of the arresting officer and of which he has reasonably trustworthy information would warrant a reasonable and prudent man in believing that a particular person has committed or is committing a crime." Brown v. State, 481 S.W.2d 106, 110 (Tex. Crim. App. 1972); see also Amores v. State, 816 S.W.2d 407, 413 (Tex. Crim. App. 1991). “Probable cause requires an evaluation of probabilities, and probabilities ‘are the factual and practical considerations of everyday life on which reasonable and prudent men, not legal technicians, act.’” Wiede, 214 S.W.3d at 24(quoting Brinegar v. United States, 338 U.S. 160, 175 (1949)). If the totality of the circumstances demonstrate a “fair probability” of finding evidence at the location being searched, then the probable cause standard is met. Dixon v. State, 206 S.W.3d 613, 616 (Tex. Crim. App. 2006). A court may consider “the training, knowledge, and experience of law enforcement officials” involved in the warrantless search. See Wiede, 214 S.W.3d at 25. Only a “minimal level of objective justification” on the part of the officer is required, and our “determination of reasonable suspicion must be based upon commonsense judgments and inferences about human behavior.” See Illinois v. Wardlow, 528 U.S. 119, 125 (2000); United States v. Sokolow, 490 U.S. 17 (1989)(quoting Immigration & Naturalization Serv. v. Dalgado, 466 U.S. 210, 217 (1984)).