This appeal raises a novel constitutional question. After traversing uncharted Fourth Amendment waters, we affirm the trial court’s denial of a passenger’s motion to suppress evidence gleaned as a result of a police stop, on bare suspicion, of a taxicab enrolled in a voluntary Boston Police Department (BPD) program designed to ensure cabdriver safety.
*4 I. BACKGROUND
Understanding this case requires familiarity with both the BPD’s Taxi Inspection Program for Safety (TIPS) and the events surrounding the traffic stop. We treat these topics separately.
A. The Program.
In 1991, responding to safety concerns accentuated by two recent murders, Boston’s police commissioner promulgated an executive order that instituted “Operation Taxi.” In terms, the order “actively encouraged” police officers “to make frequent stops of taxicabs for the purpose of checking on the operator’s safety,” especially after dark and in high-crime areas. In the order’s aftermath, however, a number of state trial judges ruled that stops made pursuant to Operation Taxi violated the constitutional proscription against unreasonable searches and seizures. See U.S. Const, amend. IV. Rather than throw out the baby with the bath water, the BPD reconfigured the program in an effort to meet the courts’ objections.
The police commissioner launched the new program, nicknamed TIPS, on September 3, 1996. The promulgating order made taxi owners’ participation voluntary and assigned responsibility for enrolling acquiescent owners to the BPD’s Hackney Carriage Unit. Owners who opted to participate were given decals and told to affix one to each of the cab’s rear side windows and a third in a conspicuous location in the rear passenger compartment. Each decal is four by five inches in size, with a bright red border, and bears the BPD shield. Each states in block print (in English and Spanish): “THIS VEHICLE MAY BE STOPPED AND VISUALLY INSPECTED BY THE BOSTON POLICE AT ANY TIME TO ENSURE DRIVER’S SAFETY.” The words “PUBLIC NOTICE” appear in enlarged letters above this statement and the words “BOSTON POLICE TAXI INSPECTION PROGRAM FOR SAFETY” appear in enlarged letters below. TIPS differs from its predecessor program in these two respects: voluntary participation and deployment of identifying decals.
The police commissioner’s order instructed uniformed and plainclothes personnel to make frequent stops of taxis that featured the decals to check on the operators’ safety. The order continued:
Stops should be conducted when and wherever necessary, particularly during the evening and early morning hours. Attention will be given to isolated and high crime areas. Taxi drivers are not to be detained longer than is necessary to check on the welfare of the operator. Passengers in occupied taxis are to be given a brief explanation of the purpose of the stop: Operator Safety. A Taxi Inspection Program for Safety form (BPD form 1833, revised 8/96) ... shall be completed at the time of the stop.
B. The Stop and its Aftermath.
TIPS was in effect shortly after midnight on January 22, 1998, when police sergeants Stephen Meade and Eric Bul-man heard a report of a shooting near the intersection of Columbia Rd. and Washington St. in the Grove Hall section of Dor-chester (a high-crime neighborhood). The officers, who were in plainclothes, drove toward that intersection in an unmarked car to offer assistance. As they neared their destination, they heard a second radio bulletin: two police officers, on foot, were pursuing an individual in the vicinity of Castlegate Rd. and Blue Hill Ave. Meade and Bulman drove there instead— the locus was only a few blocks away from the site of the reported shooting — and discovered that their fellow officers had cornered the object of their pursuit inside a building on Blue Hill Ave. The pursuing officers arrested the individual, informing Meade and Bulman that the arrest related to a drug transaction rather than to. the recent shooting.
Meade and Bulman began walking toward their car at approximately 12:40 am *5 (a half-hour after they had heard the report of the shooting). As they stood on the sidewalk, they saw a cab pull up to the corner and stop before making a right turn from Castlegate Rd. The officers noticed a passenger—defendant-appellant Ronald Woodrum—on the far side of the rear seat. He glanced in their direction and then slouched down.
Thinking that the passenger might be the perpetrator of the earlier shooting, Meade and Bulman decided to follow the taxi. They trailed the vehicle for about a block, observing that the passenger sat up straight once it had turned the corner. The officers then decided to stop the cab. They have testified that, although they were aware of the TIPS decals, their primary concern was the shooting investigation.
The officers flashed their lights and the taxi pulled to the side of the road. As Meade and Bulman walked toward it, they could see the appellant’s right shoulder go up and his left shoulder dip as he glanced down toward the left. Based on these movements, the officers suspected that the appellant was secreting a weapon inside his coat. They flanked the cab and shined flashlights into the back seat. Meade could see that the appellant’s right hand was moving around inside his coat. Meade opened the rear door closest to where Woodrum was seated, and Bulman opened the opposite door.
The appellant immediately started to protest that all he had was a beer. When he reached into his left jacket pocket with his left hand, Bulman told him not to take anything out of his coat and to put his hands in plain view. Notwithstanding this admonition, the appellant kept his right hand under his coat; Meade, concerned for his safety, directed the appellant to step outside. He grudgingly complied. When he freed his right hand and exited the taxi, a gun fell out of his jacket. At that point, the officers arrested him. Bulman and Meade filled out a TIPS form and took the appellant to the station house for booking. A search performed at that time turned up crack cocaine, a pipe, a pager, and some cash.
In due course, federal authorities charged the appellant with being a felon in possession of a firearm and ammunition, and with possessing cocaine base with intent to distribute.
See
18 U.S.C. § 922(g)(1); 21 U.S.C. § 841(a)(1). The appellant moved to suppress the physical evidence gleaned as a result of the stop, as well as evidence of incriminating statements made during his detention. Following an evidentiary hearing, the district court upheld the stop on dual grounds: first, that the circumstances gave rise to reasonable suspicion of criminal' activity, warranting the stop; and second, that TIPS legitimated it.
See United States v. Woodrum,
No. 98-10183-RGS,
II. ANALYSIS
We begin our substantive discussion with a synopsis of certain Fourth Amendment principles and then proceed to discuss this ease.
A. The Legal Landscape.
It is doctrinal bedrock that a police stop of a moving vehicle constitutes a seizure of the vehicle’s occupants and therefore comes within the purview of the Fourth Amendment.
See Whren v. United States,
The primary interests that the Fourth Amendment protects in this type of situation include an interest in freedom of movement and. a concomitant interest in being insulated from the fear and anxiety that frequently accompany a sudden, unexplained stop. These interests “are personal to all occupants of the vehicle.”
United States v. Kimball,
Absent a warrant, the policeman intrude on such an expectation only in a few carefully circumscribed kinds of situations.
See Minnesota v. Dickerson,
B. The Merits.
In this instance, the government argues that the officers’ warrantless stop of the cab was justifiable under two of these exceptions—as a “Terry stop” based on reasonable suspicion or, alternatively, as a stop premised upon the taxi owner’s consent. The district court found both arguments persuasive.
1.
Reasonable Suspicion.
To justify a stop under the reasonable-suspicion standard, the government must show “specific and articulable facts which, taken together with rational inferences from those facts, reasonably warrant that intrusion.”
Terry,
It is important to recognize that the
Terry
standard has a practical, commonsense bent. Thus, a combination of independently innocent behaviors and circumstances, both general and specific, can create reasonable suspicion in certain cases.
See Sokolow,
In this case, most of the facts underpinning the officers’ stated suspicion were not particular to the appellant. These included the recent report of a shooting, the crime-ridden neighborhood, and the hour. While such facts may put officers on their guard, they cannot alone justify a stop.
See Kimball,
The only suspect-particular observation on which the district court relied was that Woodrum tried to hide from the officers (or so they thought). The Supreme Court has held that, in some contexts, an obvious attempt to hide or to evade the authorities can be a factor in the calculus of reasonable suspicion.
See, e.g., United States v. Brignoni-Ponce,
Here, reasonable suspicion presents a question that can be argued persuasively either way. On the one hand, a slouching movement is inherently ambiguous and, for the reasons that follow, it is especially difficult to draw an inference of criminal activity from the appellant’s recession into the far corner of the back seat. Meade and Bulman were in plainclothes and standing near an unmarked vehicle. Their testimony is unilluminating as to whether any police cruisers or other identifiable police vehicles were parked at the scene or whether any uniformed police officers were in sight. The significance of the fact that an ordinary observer might not have known that the people clustered on the street corner were police may well be magnified, rather than lessened, by the totality of the circumstances: the early hour, the dangerous neighborhood, and the preva *8 lence of crime likely would make an innocent person fearful for his safety and, accordingly, desirous of anonymity.
Despite the seeming persuasiveness of this argument, there is another side to the §tory. The street-wise judgments of experienced police officers are entitled to weight, and it is at least arguable that, given the peculiar concatenation of circumstances, the appellant’s act of slouching down in the back seat, after seeing the officers, set him apart as someone who reasonably might be suspected of criminal activity.
To complicate matters further, this area of the law is in some flux. A divided Supreme Court (5-to-4) recently held that an officer was justified in suspecting a man of criminal activity when.the man was in a high-crime district and fled upon seeing the officer.
See Illinois v. Wardlow,
— U.S.-,
2. The TIPS Consent. Of course, the district court’s alternative holding also is controversial. The appellant attacks it on several fronts. He maintains, inter alia, that there was insufficient evidence to establish either the taxi owner’s or the taxi driver’s consent and that, in all events, the consent of another could not legitimate stopping him absent his consent. He also postulates that the TIPS compact impliedly conditions the driver’s employment on the sacrifice of Fourth Amendment rights and does not sufficiently limit the discretion of'the officers executing it (and is, for these reasons-, unconstitutional). Finally, he charges that, even if a TIPS consent legitimizes some stops, its scope does not extend to this stop because it was motivated by reasons apart from driver safety. These arguments warrant close perscrutation. In the end, however, we find them unpersuasive.
This case involves an unusual situation. Most of the decided cases dealing with the consent exception to the warrant requirement analyze that exception in the context of a search as opposed to a seizure.
See, e.g., Illinois v. Rodriguez,
However, when an encounter takes some appreciable time or moves to a private space (say, an interrogation room or a dwelling), the justification for the detention becomes an issue because the individual may no longer understand his participation to be voluntary.
See, e.g., Mendenhall,
The government concedes the fact of the seizure, but responds that the taxi owner’s consent to TIPS authorized it. The government, of course, has the burden of proving the voluntariness of the consent on which it relies.
See Mendenhall,
We turn, then, to the significance of this consent vis-a-vis the driver. It is at least arguable that the owner of a vehicle may authorize the kind of “safety stop” envisioned by the TIPS program over the driver’s objection.
Cf. United States v. Carter,
Here, however, we do not need to go so far as to hold that the owner’s property rights in the vehiclé and his entitlement to supervise its use legitimize all incidental intrusions occasioned by his consent to the seizure of his property. The purpose of the owner’s consent here was not to implicate the driver in wrongdoing, but, rather, to secure the driver’s safety (and, concomitantly, to preserve the value of his investment). In other words, in consenting to TIPS, the owner acted on the employee’s behalf as well as on his own.
2
This identity of interests permits us to conclude that the brief and incidental detention of the driver brought about by the consensual seizure of the owner’s property was rea
*10
sonable under the Fourth Amendment,
cf. Marshall v. Barlow’s, Inc.,
If more were needed—and we doubt that it is—the driver of the cab that the appellant hailed should not merely have expected and appreciated the consent but should have known of it. Thus, we think it fair under the circumstances to regard the driver himself as having consented to the stop. The detention involved no search and, as we have said, driver safety was implicated. Moreover, decals .festooned the vehicle, and the conspicuousness of the display put the driver squarely on notice that the owner had enrolled the cab in the TIPS program. In our view, these decals symbolized both the owner’s and the driver’s consent to future stops.
The appellant attempts to parry these thrusts by insisting that, regardless of notice, the owner’s initiative effectively abrogated the driver’s Fourth Amendment right to resist searches and seizures, and that this abrogation imposed an unconstitutional condition on the employment relationship. This contention cannot withstand scrutiny. In the first place, the record contains no evidence that consent was a condition of employment. Thus, we do not know whether a nonconsenting driver would have been discharged or, in the alternative, permitted to remove the TIPS decals. In the second place, the appellant’s position rests on an unstable legal foundation. Although public employers ordinarily cannot condition employment on an employee’s consent to a search,
see Pickering v. Board of Educ.,
We next inquire whether the owner’s and driver’s consent may justify a TIPS stop even though no positive consent has been obtained from the passenger. The district court answered this query affirmatively on the ground that “[t]he operator of a taxi ... has the authority to consent to its search over the objection of his passenger.”
Woodrum,
At times, an individual can consent to an intrusion that affects another’s constitutionally protected interests without overstepping the bounds of the Fourth Amendment. Thus, for example, when two persons share common authority over premises or effects, one party’s consent legitimates a warrantless search even if . the search is aimed at ferreting out evidence of the other party’s malefactions.
See Matlock,
Common authority is, of course, not to be implied from the mere property interest a third party has in the property, ... but rests rather on mutual use of the property by persons generally having joint access or control for most purposes, so that it is reasonable to recognize that ány of the co-inhabitants has the right to permit the inspection in his own right and that the others have assumed the risk that one of their number might permit the common area to be searched.
Id.
at 171 n. 7,
*11 Up to now, this principle has found expression only in the context of consents to the search of property—but there is no sound reason to restrict the principle rigidly to that milieu. As this case illustrates, the logic of third-party consent can be adapted to seizures in some circumstances.
Freedom of movement is one of the foremost interests impugned by a traffic stop,
see Kimball,
To be sure, this does not mean that a taxicab passenger assumes the risk of every type of seizure. The actions taken pursuant to the consent must be reasonable—and the Supreme Court has made it clear that “[t]he reasonableness of seizures that are less intrusive than a traditional arrest depends on a balance between the public interest and the individual’s right to personal security free from arbitrary interference by law officers.”
Brown v. Texas,
In this instance, we conclude that the nature of TIPS makes the operator’s consent a reasonable justification for stopping a taxicab (even though the stop involves, as we have said, a seizure of both the driver and the passenger). After all, TIPS came into being as a considered response to grave safety concerns; many taxi drivers had been robbed and two had been murdered. Given the obvious public interest in preventing such incidents, this history weighs heavily in constructing the requisite balance.
Moreover, the consent does not leave stops to the officers’ unfettered discretion. The order issued to police personnel specifies that TIPS stops are to be conducted only “when ... necessary” to check on the taxi operator’s safety. The record contains unrebutted testimony that this language accurately characterizes the actual
*12
implementation of the program.
4
Since police officers are constrained by that directive, we must regard a taxi owner’s consent to TIPS stops as narrow in scope and purpose.
See id.
at 251,
On the other pan of the scale, we weigh the rather modest intrusion on passengers’ liberty that TIPS entails. According to the officers’ uncontradicted testimony, TIPS stops are usually brief and involve only limited inquiries to the driver and a quick visual inspection of the cab’s interior. Objectively viewed, the intrusion is slight.
See Martinez-Fuerte,
We find more nettlesome the subjective aspects of the intrusion, as a reasonable passenger might well experience fear or anxiety in the interval between a stop and an officer’s explanation.
See Delaware v. Prouse,
Assaying all of these competing considerations, we conclude that a seizure which occurs in the form of a voluntary, properly conducted TIPS stop passes the Supreme Court’s balancing test. Consequently, we find the application of the third-party consent principle compelling and we hold that a police officer’s stop of a taxicab displaying TIPS decals for purposes of checking on the driver’s safety is reasonably justified by the owner’s consent, notwithstanding the presence of a passenger in the cab who has not given any express consent.
The question remains whether this particular stop was justified by the taxi owner’s consent. In this connection, the appellant’s major premise is that the stop was not within the ambit of the consent because its impetus lay in the officers’ desire to investigate a recent shooting rather than their desire to assure the driver’s safety. The appellant’s minor premise is that the officers effectively vitiated the consent by their failure after the initial stop to follow TIPS protocol.
We begin our analysis of these matters by reviewing what transpired below. The district court ruled that the officers’ subjective motivations did not matter; the stop was constitutional, the court reasoned, as long as the officers could have stopped the taxi constitutionally.
See Woodrum,
We cannot accept the district court’s approach. Unlike in Whren, the purpose of the stop matters here. Because the authority provided by the consent was limited, the officers’ reasons for effecting the stop are relevant to whether the consent legitimated it. A consent to TIPS probably would not justify, for example, a stop aimed at questioning a docile eyewitness to a recent crime or one aimed at collaring an illegal alien not thought to be dangerous.
Despite our disagreement with the lower court, we hold that the stop was within the purview of the consent. The scope of a consent is determined by what a reasonable person would think it to be.
See Jimeno,
We need not linger over the appellant’s minor premise. We already have determined that the initial stop did not in any way offend the Fourth Amendment. From that point forward, the officers’ actions were fully justified by reasonable suspicion. Thus, any deviations from the TIPS protocol that may have transpired after the initial stop were of no moment. We explain briefly.
As the officers approached the taxi, they saw the appellant lean down toward his left side and they reasonably suspected that he was concealing a weapon inside his jacket. Then, when they peered into the back seat, they saw the appellant’s right hand moving around underneath his jacket. This is exactly the kind of situation in which an officer’s experience deserves deference.
See, e.g., United States v. Mitchell,
That ends the matter. Once the appellant exited the vehicle, the weapon tum *14 bled into plain view, and the officers had every right to act on what they saw.
III. CONCLUSION
We need go no further. The taxi owner’s consent to TIPS authorized the police to stop the taxi in which the appellant was riding on the mere suspicion that a dangerous felon might be inside. The officers’ actions after the stop were legitimated by reasonable suspicion that the appellant was carrying a weapon and by caution for their own safety. Neither the stop nor the officers’ subsequent actions offended the Constitution. Hence, we uphold the district court’s denial of the motion to suppress evidence gleaned therefrom.
Affirmed.
Notes
. This directness distinguishes this case from cases in which courts are asked to imply the owner's consent indirectly from his voluntary undertaking to do something that he has been warned might lead to a search or seizure.
See, e.g., McGann v. Northeast Ill. Reg’l Commuter R.R. Corp.,
. Indeed, the taxi owner’s consent reasonably can be viewed as a fulfillment of his employment-related duty to provide a safe workplace for his drivers. After all, the drivers' safety is a work-related interest of the employer, unlike an abstract interest in cooperating with police to abate crime in general, and employees can expect an employer to seek police assistance in protecting the former interest even if consent to a criminal investigation of their outside activities would be suspect.
See Collins,
. This mutuality of control of the vehicle’s movement distinguishes this situation from cases such as
Stoner v. California,
. Because we construe the program in the light most favorable to constitutionality,
see Almeida-Sanchez v. United States,
. To be sure, one officer testified that he would have made the stop even if the taxi did not have TIPS emblemata — a course of action that would have had no discernible legal justification. But that testimony does not affect the outcome of this appeal. We concern ourselves with what was, not with what might have been.
See Proctor,
