Is reasonable suspicion sufficient to justify a stop?

Whether police officers had reasonable suspicion to justify a stop is a mixed question of law and fact which is reviewed de novo. United States v. Hernandez-Alvarado, 891 F.2d 1414, 1416 (9th Cir.1989). "An officer may make an investigatory stop if he is aware of specific, articulable facts which, together with objective and reasonable inferences, form a basis for suspecting that the particular person is engaged in criminal activity." Id. In determining reasonable suspicion, we consider "the totality of the circumstances--the whole picture." United States v. Sokolow, 490 U.S. 1 (1988) (quoting United States v. Cortez, 449 U.S. 411, 417 (1981)).