What is the basis for a motion to suppress search and seizure evidence in a federal criminal case?

As previously noted, the principal issue is the validity of the traffic stop and the patdown search which followed. The defendant had already been through part of this legal routine growing out of this same incident when he first failed in a preliminary hearing in a state court prosecution to have the search evidence suppressed. The defendant had been held for state trial on the drug charges, but the state charges were dismissed in favor of this federal prosecution. In this prosecution, the district court denied the defendant's motion to suppress the same evidence on the same grounds as had the state court, and which we now examine. We must analyze the stop and the frisk separately and determine the reasonableness of each independently. United States v. Thomas , 863 F.2d 622, 628 (9th Cir. 1988).

A. The Vehicle Stop