B. Mexican Appearance and Reasonable Suspicion of Illegal Alien Status
Racial profiling occurs when law enforcement personnel suspect illegal activity by using a person's physical appearance or the stereotypical perceptions of an ethnic or racial group. In United States v. Brignoni-Ponce, the Court addressed the permissibility of an officer on a roving patrol to stop a vehicle and question its occupants when the only ground for suspicion is that the occupants appeared to be of Mexican ancestry. In rejecting this police practice, the Court added that, except at the border and its functional equivalents, roving patrol officers may stop vehicles only if they are aware of specific articulable facts, together with rational inferences from those facts, that reasonably warrant suspicion that the vehicles contain aliens who may be illegally in the country. The Supreme Court deemed the stop and interrogation to be not reasonable under the Fourth Amendment, adding that law enforcement's legitimate needs do not require such interference with lawful traffic:
Roads near the border carry not only aliens seeking to enter the country illegally, but a large volume of legitimate traffic as well. . . . To approve roving-patrol stops of all vehicles in the border area, without any suspicion that a particular vehicle is carrying illegal immigrants, would subject the residents of these and other areas to potentially unlimited interference with their use of the highways, solely at the discretion of Border Patrol officers.
Furthermore, the Court observed that significant numbers of native-born and naturalized citizens have the physical characteristics identified with Mexican ancestry and emphasized that, even though Mexican appearance [is] a relevant factor, standing alone it does not justify stopping all Mexican-Americans to ask if they are aliens.