Based on their discovery of sets of distinctive human footprints
in the desert, Border Patrol officers deduced that on a number of
occasions groups of from 8 to 20 persons had been guided by a
person, whom they designated "Chevron," from Mexico across an area
of desert in Arizona, known to be heavily trafficked by aliens
illegally entering the country. These groups of aliens proceeded to
an isolated point on a road to be picked up by a vehicle; the
officers deduced the vehicle probably approached from the east and
returned to the east after the pickup. They also surmised, based on
the times when the distinctive tracks were discovered, that
"Chevron" generally traveled on clear nights during or near
weekends, and arrived at the pickup point between 2 a.m. and 6 a.m.
On the basis of this information, the officers stationed themselves
at a point east of the probable pickup point on a night when they
believed there was a strong possibility that "Chevron" would be
smuggling aliens. The officers observed a pickup truck with a
camper shell suitable for carrying sizable groups pass them heading
west, and then observed the same vehicle return within the
estimated time for making a round trip to the pickup point. The
officers stopped the vehicle, which was being driven by respondent
Cortez and in which respondent Hernandez-Loera, who was wearing
shoes with soles matching the distinctive "chevron" shoeprint, was
a passenger. Cortez voluntarily opened the door of the camper, and
the officers then discovered illegal aliens. Prior to trial on
charges of transporting illegal aliens, respondents sought to
suppress the evidence of the presence of the aliens discovered as a
result of the stopping of their vehicle, contending that the
officers did not have adequate cause to make the investigative
stop. The District Court denied the motion, and respondents were
convicted. The Court of Appeals reversed, holding that the officers
lacked a sufficient basis to justify stopping the vehicle, and thus
respondents' Fourth Amendment rights were violated.
The objective facts and circumstantial evidence
justified the investigative stop of respondents' vehicle. Pp.
449 U. S.
(a) In determining what cause is sufficient to authorize police
to stop a person, the totality of the circumstances -- the whole
picture -- must be taken into account. Based upon that whole
picture, the detaining
Page 449 U. S. 412
officers must have a particularized and objective basis for
suspecting the particular person stopped of criminal activity. The
process of assessing all of the circumstances does not deal with
hard certainties, but with probabilities, and the evidence
collected must be weighed as understood by those versed in the
field of law enforcement. Also, the process must raise suspicion
that the particular individual being stopped is engaged in
wrongdoing. Pp. 449 U. S.
(b) This case implicates all of these principles -- especially
the imperative of recognizing that, when used by trained law
enforcement officers, objective facts, meaningless to the
untrained, allow for permissible deductions from such facts to
afford a legitimate basis for suspicion of a particular person and
action on that suspicion. Pp. 449 U. S.
(c) The intrusion upon privacy associated with this stop was
limited, and "reasonably related in scope to the justification for
[its] initiation." Terry v. Ohio, 392 U. S.
, 392 U. S. 29
Based upon the whole picture, the officers, as experienced Border
Patrol agents, could reasonably surmise that the particular vehicle
they stopped was engaged in criminal activity. Pp. 449 U. S.
595 F.2d 505, reversed.
BURGER, C.J., delivered the opinion of the Court, in which
BRENNAN, WHITE, BLACKMUN, POWELL, REHNQUIST, and STEVENS, JJ.,
joined. STEWART, J., filed an opinion concurring in the result,
p. 449 U. S. 422
MARSHALL, J., concurred in the judgment.
CHIEF JUSTICE BURGER delivered the opinion of the Court.
We granted certiorari, 447 U.S. 904, to consider whether
objective facts and circumstantial evidence suggesting that a
particular vehicle is involved in criminal activity may provide
Page 449 U. S. 413
a sufficient basis to justify an investigative stop of that
Late in 1976, Border Patrol officers patrolling a sparsely
populated section of southern central Arizona found human
footprints in the desert. In time, other sets of similar footprints
were discovered in the same area. From these sets of footprints, it
was deduced that, on a number of occasions, groups of from 8 to 20
persons had walked north from the Mexican border, across 30 miles
of desert and mountains, over a fairly well-defined path, to an
isolated point on Highway 86, an east-west road running roughly
parallel to the Mexican border.
Officers observed that one recurring shoeprint bore a
distinctive and repetitive V-shaped or chevron design. Because the
officers knew from recorded experience that the area through which
the groups passed was heavily trafficked by aliens illegally
entering the country from Mexico, they surmised that a person, to
whom they gave the case-name "Chevron," was guiding aliens
illegally into the United States over the path marked by the tracks
to a point where they could be picked up by a vehicle.
The tracks led into or over obstacles that would have been
avoided in daylight. From this, the officers deduced that "Chevron"
probably led his groups across the border and to the pickup point
at night. Moreover, based upon the times when they had discovered
the distinctive sets of tracks, they concluded that "Chevron"
generally traveled during or near weekends, and on nights when the
weather was clear.
Their tracking disclosed that, when "Chevron's" groups came
within 50 to 75 yards of Highway 86, they turned right and walked
eastward, parallel to the road. Then, approximately at highway
milepost 122, the tracks would turn north and disappear at the
road. From this pattern, the officers concluded that the aliens
very likely were picked up by a vehicle
Page 449 U. S. 414
-- probably one approaching from the east, for, after a long
overland march, the group was most likely to walk parallel to the
highway toward the approaching vehicle. The officers also concluded
that, after the pickup, the vehicle probably returned to the east,
because it was unlikely that the group would be walking away from
its ultimate destination.
On the Sunday night of January 30-31, 1977, Officers Gray and
Evans, two Border Patrolmen who had been pursuing the investigation
of "Chevron," were on duty in the Casa Grande area. The latest set
of observed "Chevron" tracks had been made on Saturday night,
January 15-16. January 30-31 was the first clear night after three
days of rain. For these reasons, Gray and Evans decided there was a
strong possibility that "Chevron" would lead aliens from the border
to the highway that night.
The officers assumed that, if "Chevron" did conduct a group that
night, he would not leave Mexico until after dark, that is, about 6
p.m. They knew from their experience that groups of this sort,
traveling on foot, cover about two and a half to three miles an
hour. Thus, the 30-mile journey would take from 8 to 12 hours. From
this, the officers calculated that "Chevron" and his group would
arrive at Highway 86 somewhere between 2 a.m. and 6 a.m. on January
About 1 a.m., Gray and Evans parked their patrol car on an
elevated location about 100 feet off Highway 86 at milepost 149, a
point some 27 miles east of milepost 122. From their vantage point,
the officers could observe the Altar Valley, an adjoining territory
they had been assigned to watch that night, and they also could see
vehicles passing on Highway 86. They estimated that it would take
approximately one hour and a half for a vehicle to make a round
trip from their vantage point to milepost 122. Working on the
hypothesis that the pickup vehicle approached milepost 122 from the
east and thereafter returned to its starting point, they focused
upon vehicles that passed them from the east,
Page 449 U. S. 415
and, after about one hour and a half, passed them returning to
Because "Chevron" appeared to lead groups of between 8 and 20
aliens at a time, the officers deduced that the pickup vehicle
would be one that was capable of carrying that large a group
without arousing suspicion. For this reason, and because they knew
that certain types of vehicles were commonly used for smuggling
sizable groups of aliens, they decided to limit their attention to
vans, pickup trucks, other small trucks, campers, motor homes, and
Traffic on Highway 86 at milepost 149 was normal on the night of
the officers' surveillance. In the 5-hour period between 1 a.m. and
6 a.m., 15 to 20 vehicles passed the officers heading west, toward
milepost 122. Only two of them -- both pickup trucks with camper
shells -- were of the kind that the officers had concluded
"Chevron" would likely use if he was to carry aliens that night.
One, a distinctively colored pickup truck with a camper shell,
passed for the first time at 4:30 a.m. Officer Gray was able to see
and record only a partial license number, "GN 88__." [Footnote 1
] At 6:12 a.m., almost exactly the
estimated one hour and a half later, a vehicle looking like this
same pickup passed them again, this time heading east.
The officers followed the pickup and were satisfied from its
license plate, "GN 8804," that it was the same vehicle that had
passed at 4:30 a.m. At that point, they flashed their police lights
and intercepted the vehicle. Respondent Jesus Cortez was the driver
and owner of the pickup; respondent Pedro Hernandez-Loera was
sitting in the passenger's seat. Hernandez-Loera was wearing shoes
with soles matching the distinctive "chevron" shoeprint.
The officers identified themselves and told Cortez they were
conducting an immigration check. They asked if he was
Page 449 U. S. 416
carrying any passengers in the camper. Cortez told them he had
picked up some hitchhikers, and he proceeded to open the back of
the camper. In the camper, there were six illegal aliens. The
officers then arrested the respondents.
Cortez and Hernandez-Loera were charged with six counts of
transporting illegal aliens in violation of 8 U.S.C. § 1324(a). By
pretrial motion, they sought to suppress the evidence obtained by
Officers Gray and Evans as a result of stopping their vehicle. They
argued that the officers did not have adequate cause to make the
investigative stop. The District Court denied the motion. A jury
found the respondents guilty as charged. They were sentenced to
concurrent prison terms of five years on each of six counts. In
addition, Hernandez-Loera was fined $12,000.
A divided panel of the Court of Appeals for the Ninth Circuit
reversed, holding that the officers lacked a sufficient basis to
justify the stop of the pickup. 595 F.2d 505 (1979). That court
recognized that United States v. Brignoni-Ponce,
422 U. S. 873
(1975), provides a standard governing investigative stops of the
kind involved in this case, stating:
"The quantum of cause necessary in . . . cases [like this one]
was established . . . in United States v. Brignoni-Ponce.
. . ."
"[O]fficers on roving patrol 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
595 F.2d at 507 (quoting United States v. Brignoni-Ponce,
at 422 U. S. 884
(citations omitted). The court also recognized that "the ultimate
question on appeal is whether the trial judge's finding that
founded suspicion was present here was clearly erroneous." 595 F.2d
at 507. Here, because, in the view of the facts of the two judges
constituting the majority, "[t]he officers did not have a valid
basis for singling out the Cortez vehicle," id.
Page 449 U. S. 417
the circumstances admitted "far too many innocent inferences to
make the officers' suspicions reasonably warranted,"
the panel concluded that the stop of Cortez'
vehicle was a violation of the respondents' rights under the Fourth
Amendment. In dissent, Judge Chambers was persuaded that
recognized the validity of permitting an
officer to assess the facts in light of his past experience.
The Fourth Amendment applies to seizures of the person,
including brief investigatory stops such as the stop of the vehicle
here. Reid v. Georgia, 448 U. S. 438
448 U. S. 440
(1980); United States v. Brignoni-Ponce, supra
422 U. S. 878
Davis v. Mississippi, 394 U. S. 721
(1969); Terry v. Ohio, 392 U. S. 1
392 U. S. 16
(1968). An investigatory stop must be justified by some objective
manifestation that the person stopped is, or is about to be,
engaged in criminal activity. [Footnote 2
] Brown v. Texas, 443 U. S.
, 443 U. S. 51
(1979); Delaware v. Prouse, 440 U.
, 440 U. S. 661
(1979); United States v. Brignoni-Ponce, supra
422 U. S. 884
Adams v. Williams, 407 U. S. 143
407 U. S.
-149 (1972); Terry v. Ohio, supra
392 U. S.
Courts have used a variety of terms to capture the elusive
concept of what cause is sufficient to authorize police to stop a
person. Terms like "articulable reasons" and "founded suspicion"
are not self-defining; they fall short of providing clear guidance
dispositive of the myriad factual situations that arise. But the
essence of all that has been written 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
Page 449 U. S. 418
activity. See, e.g., Brown v. Texas, supra
443 U. S. 51
United States v. Brignoni-Ponce, supra
at 422 U. S.
The idea that an assessment of the whole picture must yield a
particularized suspicion contains two elements, each of which must
be present before a stop is permissible. First, the assessment must
be based upon all of the circumstances. The analysis proceeds with
various objective observations, information from police reports, if
such are available, and consideration of the modes or patterns of
operation of certain kinds of lawbreakers. From these data, a
trained officer draws inferences and makes deductions -- inferences
and deductions that might well elude an untrained person.
The process does not deal with hard certainties, but with
probabilities. Long before the law of probabilities was articulated
as such, practical people formulated certain common sense
conclusions about human behavior; jurors as factfinders are
permitted to do the same -- and so are law enforcement officers.
Finally, the evidence thus collected must be seen and weighed not
in terms of library analysis by scholars, but as understood by
those versed in the field of law enforcement.
The second element contained in the idea that an assessment of
the whole picture must yield a particularized suspicion is the
concept that the process just described must raise a suspicion that
the particular individual being stopped is engaged in wrongdoing.
Chief Justice Warren, speaking for the Court in Terry v. Ohio,
"[t]his demand for specificity in the information upon which
police action is predicated is the central teaching of this
Court's Fourth Amendment jurisprudence.
at 392 U. S. 21
18 (emphasis added). See also Brown v. Texas, supra
443 U. S. 51
Delaware v. Prouse, supra
at 440 U. S.
-663; United States v. Brignoni-Ponce, supra
at 422 U. S.
This case portrays at once both the enormous difficulties of
patrolling a 2,000-mile open border and the patient skills
Page 449 U. S. 419
needed by those charged with halting illegal entry into this
country. It implicates all of the principles just discussed --
especially the imperative of recognizing that, when used by trained
law enforcement officers, objective facts, meaningless to the
untrained, can be combined with permissible deductions from such
facts to form a legitimate basis for suspicion of a particular
person and for action on that suspicion. We see here the kind of
police work often suggested by judges and scholars as examples of
appropriate and reasonable means of law enforcement. Here, fact on
fact and clue on clue afforded a basis for the deductions and
inferences that brought the officers to focus on "Chevron."
Of critical importance, the officers knew that the area was a
crossing point for illegal aliens. They knew that it was common
practice for persons to lead aliens through the desert from the
border to Highway 86, where they could -- by prearrangement -- be
picked up by a vehicle. Moreover, based upon clues they had
discovered in the 2-month period prior to the events at issue here,
they believed that one such guide, whom they designated "Chevron,"
had a particular pattern of operations.
By piecing together the information at their disposal, the
officers tentatively concluded that there was a reasonable
likelihood that "Chevron" would attempt to lead a group of aliens
on the night of Sunday, January 30-31. Someone with chevron-soled
shoes had led several groups of aliens in the previous two months,
yet it had been two weeks since the latest crossing. "Chevron,"
they deduced, was therefore due reasonably soon. "Chevron" tended
to travel on clear weekend nights. Because it had rained on the
Friday and Saturday nights of the weekend involved here, Sunday was
the only clear night of that weekend; the officers surmised it was
therefore a likely night for a trip.
Once they had focused on that night, the officers drew upon
other objective facts known to them to deduce a timeframe
Page 449 U. S. 420
within which "Chevron" and the aliens were likely to arrive.
From what they knew of the practice of those who smuggle aliens,
including what they knew of "Chevron's" previous activities, they
deduced that the border crossing and journey through the desert
would probably be at night. They knew the time when sunset would
occur at the point of the border crossing; they knew about how long
the trip would take. They were thus able to deduce that "Chevron"
would likely arrive at the pickup point on Highway 86 in the
timeframe between 2 a.m. and 6 a.m.
From objective facts, the officers also deduced the probable
point on the highway -- milepost 122 -- at which "Chevron" would
likely rendezvous with a pickup vehicle. They deduced from the
direction taken by the sets of "Chevron" footprints they had
earlier discovered that the pickup vehicle would approach the
aliens from, and return with them to, a point east of milepost 122.
They therefore staked out a position east of milepost 122 (at
milepost 149) and watched for vehicles that passed them going west
and then, approximately one and a half hours later, passed them
again, this time going east.
From what they had observed about the previous groups guided by
the person with "chevron" shoes, they deduced that "Chevron" would
lead a group of 8 to 20 aliens. They therefore focused their
attention on enclosed vehicles of that passenger capacity.
The analysis produced by Officers Gray and Evans can be
summarized as follows: if, on the night upon which they believed
"Chevron" was likely to travel, sometime between 2 a.m. and 6 a.m.,
a large enclosed vehicle was seen to make an east-west-east round
trip to and from a deserted point (milepost 122) on a deserted road
(Highway 86), the officers would stop the vehicle on the return
trip. In a 4-hour period, the officers observed only one vehicle
meeting that description. And it is not surprising that, when they
Page 449 U. S. 421
vehicle on its return trip, it contained "Chevron" and several
illegal aliens. [Footnote
The limited purpose of the stop in this case was to question the
occupants of the vehicle about their citizenship and immigration
status and the reasons for the round trip in a short timespan in a
virtually deserted area. No search of the camper or any of its
occupants occurred until after respondent Cortez voluntarily opened
the back door of the camper; thus, only the stop, not the search,
is at issue here. The intrusion upon privacy associated with this
stop was limited, and was "reasonably related in scope to the
justification for [its] initiation," Terry v. Ohio,
U.S. at 392 U. S. 29
We have recently held that stops by the Border Patrol may he
justified under circumstances less than those constituting probable
cause for arrest or search. United States v.
422 U.S. at 422 U. S. 880
] Thus, the test is
not whether Officers Gray and Evans had probable cause to conclude
that the vehicle they stopped would contain "Chevron" and a group
of illegal aliens. Rather, the question is whether, based upon the
whole picture, they, as experienced Border Patrol officers, could
reasonably surmise that the particular vehicle
Page 449 U. S. 422
they stopped was engaged in criminal activity. On this record,
they could so conclude.
JUSTICE MARSHALL concurs in the judgment.
The second camper passed them 15 or 20 minutes later. As far as
the record shows, it did not return.
Of course, an officer may stop and question a person if there
are reasonable grounds to believe that person is wanted for past
In United States v. Brignoni-Ponce, 422 U.
, 422 U. S.
-885 (1975), the Court listed several factors to be
considered as part of the totality of the circumstances in
determining the existence vel non
of a particularized
suspicion in cases treating official attempts to stem the influx of
illegal aliens into our country. Though the list did not purport to
be exhaustive, it is noteworthy that several of the factors present
here were recognized by Brignoni-Ponce
as significant in
this context; for example, information about recent border
crossings and the type of vehicle involved.
The wide public interest in effective measures to prevent the
entry of illegal aliens at the Mexican border has been cataloged by
this Court. See, e.g., United States v. Ortiz,
422 U. S. 891
422 U. S.
-914 (1975) (BURGER, C.J., concurring in judgment);
United States v. Brignoni-Ponce, supra,
at 422 U. S.
JUSTICE STEWART, concurring in the result.
The Border Patrol officers in this case knew, or had rationally
deduced, that "Chevron" had repeatedly shepherded illegal aliens up
from the border; that his treks had commonly ended early in the
morning around milepost 122 on Highway 86; that he usually worked
on weekends; that he probably had made no trips for two weeks; and
that trips were most likely when the weather was good. Knowing of
this pattern, the officers could reasonably anticipate, even if
they could not guarantee, the arrival of another group of aliens,
led by Chevron, at milepost 122 on the first clear weekend night in
late January, 1977. Route 86 leads through almost uninhabited
country, so little traveled in the hours of darkness that only 15
to 20 westbound vehicles passed the police during the five hours
they watched that Sunday night. Only two vehicles capacious enough
to carry a sizable group of illegal aliens went by. One of those
two vehicles not only drove past them, but returned in the opposite
direction after just enough time had elapsed for a journey to
milepost 122 and back. This nocturnal round trip into "desolate
desert terrain" would in any event have been puzzling. Coming when
and as it did, surely the most likely explanation for it was that
Chevron was again shepherding aliens.
In sum, the Border Patrol officers had discovered an abundance
of "specific articulable facts" which, "together with rational
inferences from [them]," entirely warranted a "suspicion that the
vehicl[e] contain[ed] aliens who [might] be illegally in the
country." United States v.
Page 449 U. S. 423
422 U. S. 873
422 U. S. 884
Because the information possessed by the officers thus met the
requirements established by the Brignoni-Ponce
the kind of stop made here, I concur in the reversal of the
judgment of the Court of Appeals.