In United States v. Cortez (1981) 449 U.S. 411, 418, the border patrol was investigating a particular group that was smuggling illegal aliens across the border. The border patrol learned the following facts during a two-month investigation. The area they were investigating was a border crossing for illegal aliens. They had over a period of time located numerous tracks of individuals all headed from the Mexican border that terminated near a specific point at Highway 86. Because they terminated at the highway, the officers concluded that a vehicle picked up the groups. One set of footprints, which appeared repeatedly, left an impression with a distinctive pattern. The investigating officers designated this person "Chevron" and concluded he was the guide. Because the tracks often led into dead ends that required backtracking by the groups, and these areas would easily be avoided in daylight, the officers concluded the trips were made at night. The officers determined by examining the tracks that the groups usually contained between 8 and 20 individuals. Based on the times when they discovered "Chevron's" tracks, the officers determined that "Chevron" usually led groups across the border during or near weekends and on nights when the weather was clear. The investigating officers were on duty on a Sunday night in late January. The absence of "Chevron's" tracks revealed that his last border crossing was in early January. The night in question was the first clear night after three days of rain. The officers concluded there was a strong possibility that "Chevron" would make a crossing that night. The officers assumed that if "Chevron" made a crossing that night he would leave Mexico after dark. They estimated the time it would take to make the crossing by those on foot and determined that "Chevron" would reach the pick-up point between 2 a.m. and 6 a.m. that morning. The officers also determined that the pick-up vehicle would approach the pick-up point from the east, and return to the east since that was the direction the groups were walking before they were picked up and it was unlikely that the groups would walk away from their ultimate destination. On the night in question, the officers began their surveillance of Highway 86 approximately 27 miles east from the pick-up point. The officers were looking for a vehicle large enough to carry groups of illegal aliens without drawing unwanted attention, such as pick-ups, vans, motor homes, campers and like vehicles. They also were looking for a vehicle which headed west bound, and then returned east bound within one and one half hours, the time they estimated it would take to make the round trip from their vantage point to the pick-up point. Only one distinctive camper met the criteria established by the officers. When the officers stopped the vehicle, they found six illegal aliens in the camper and an individual wearing shoes that matched the pattern of "Chevron's" shoes in the cab. The United States Supreme Court held that the above facts established probable cause for the stop of the vehicle. The Court began by reiterating that the Fourth Amendment applied to brief investigatory stops such as the one at issue here. ( United States v. Cortez, supra, 449 U.S. at p. 417.) They also reiterated that the essence of Fourth Amendment analysis ". . . is that the totality of the circumstances--the whole picture--must be taken into account. Based upon that whole picture the detaining officers must have a particularized and objective basis for suspecting the particular person stopped of criminal activity." ( Id. at pp. 417-418.) The Court concluded the officers used objective facts to draw permissible inferences to form a legitimate basis for suspicion of a particular person and for action on that suspicion. ( Id. at p. 419.) The Court held that, based on the whole picture of the two-month investigation, these experienced Border Patrol agents could reasonably surmise that the particular vehicle they stopped was engaged in criminal activity. ( Id. at pp. 421-422.) The United States Supreme Court cautioned that investigatory seizures based upon suspicion short of probable cause must be temporary and last no longer than is necessary to effectuate the purpose of the initial stop. The investigative methods employed should be the least intrusive means reasonably available to verify or dispel an officer's suspicion in a short period of time. The scope of the intrusion permitted obviously will vary depending upon the particular facts and circumstances of each case. United States v. Cortez, supra, 449 U.S. at 411.