United States v. Mosley

Opinions of the United
2006 Decisions States Court of Appeals
for the Third Circuit

7-21-2006

USA v. Mosley
Precedential or Non-Precedential: Precedential

Docket No. 05-1519

Follow this and additional works at: http://digitalcommons.law.villanova.edu/thirdcircuit_2006

Recommended Citation
"USA v. Mosley" (2006). 2006 Decisions. Paper 649.
http://digitalcommons.law.villanova.edu/thirdcircuit_2006/649

This decision is brought to you for free and open access by the Opinions of the United States Court of Appeals for the Third Circuit at Villanova
University School of Law Digital Repository. It has been accepted for inclusion in 2006 Decisions by an authorized administrator of Villanova
University School of Law Digital Repository. For more information, please contact Benjamin.Carlson@law.villanova.edu.
 PRECEDENTIAL

UNITED STATES COURT OF APPEALS
FOR THE THIRD CIRCUIT

No. 05-1519

UNITED STATES OF AMERICA

v.

ROBERT MOSLEY,

Appellant

On Appeal from the United States District Court
for the Eastern District of Pennsylvania
(D.C. No. 04-cr-00190)
District Judge: Honorable John R. Padova

Argued June 15, 2006
Before: FISHER, CHAGARES and
REAVLEY,* Circuit Judges.

(Filed: July 21, 2006)

*
The Honorable Thomas M. Reavley, United States
Circuit Judge for the Fifth Circuit, sitting by designation.
David L. McColgin
Brett G. Sweitzer (Argued)
Defender Association of Philadelphia
Federal Court Division
601 Walnut Street
The Curtis Center, Suite 540 West
Philadelphia, PA 19106
Attorneys for Appellant

Jennifer A. Williams (Argued)
Office of United States Attorney
615 Chestnut Street, Suite 1250
Philadelphia, PA 19106
Attorney for Appellee

OPINION OF THE COURT

FISHER, Circuit Judge.

We are presented here with a casebook-ready fact pattern
implicating an area of Fourth Amendment law that has long
been a source of confusion. Today we explain, as clearly as we
can, how the exclusionary rule applies in cases in which
evidence obtained during an illegal traffic stop is introduced
against a passenger with no possessory interest in the vehicle.

We hold that when a vehicle is illegally stopped by the
police, no evidence found during the stop may be used by the

2
government against any occupant of the vehicle unless the
government can show that the taint of the illegal stop was
purged. The metaphorical bubble of causation encapsulates the
entire vehicle and links the illegality of the stop to the Fourth
Amendment rights of all of the occupants.

In so holding, we join all of our sister circuits that have
directly faced this issue. We will canvass that caselaw, and
explain why we agree with it.

I.

On the night of October 28, 2003, Robert Mosley went to
the Diamond Dolls nightclub in Philadelphia with his nephew
Jerome Small, who drove. While they were at the club, Small
received a telephone call from a romantic acquaintance, and told
Mosley that he was leaving the club to go meet her. Not
wanting to leave Mosley without a ride home, Small introduced
Mosley to his friend Julian Hayes, who agreed to drop Mosley
off on his way home. At around 1:30 a.m., Mosley left the club
with Hayes and Erica Scott, a dancer at the club who was
accompanying Hayes. Hayes and Scott got in the front seat of
Hayes’ vehicle, a green Suzuki SUV, and Mosley got in the
back.

At about the same time, a police radio call went out
advising officers to be on the lookout for a black man with
dreadlocks driving a green SUV. The source of the information
relayed in the radio call is not reflected in the record. Police
officers on patrol in the neighborhood of the nightclub heard the
call and shortly thereafter saw Hayes’ SUV, a green SUV with

3
a black driver, as it was pulling away from the nightclub. They
immediately pulled the car over. Upon approaching the car, the
responding officers observed a gun on the floor under the
driver’s seat. They then ordered Hayes, Scott, and Mosley to get
out of the car, and searched it, recovering a second gun from
the front seat, two from the floorboards of the back seat area,
and one from the back seat itself. Hayes and Mosley were
arrested and charged with gun possession.

However, the Supreme Court has held that anonymous
tips do not provide sufficient justification for an investigatory
stop, see Florida v. J.L., 529 U.S. 266 (2000), and the officers
did not observe Hayes committing any traffic violation that
would have justified the stop under Whren v. United States, 517
U.S. 806 (1996). The government conceded that the stop was
illegal, and dropped all charges against Hayes.

The government proceeded, however, with the gun
possession case against Mosley, arguing that because he was a
passenger in the vehicle, he could not seek to suppress the guns,
notwithstanding the illegality of the stop. Mosley contended
that insofar as he had been illegally seized by the traffic stop, he
should have the same suppression claim as Hayes. The District
Court agreed with the government, and admitted into evidence
the guns found in the back seat of the vehicle.1 Mosley was
convicted under 18 U.S.C. § 922(g) for possessing a firearm

1
The jury specially found that Mosley had possessed only
the gun that was on the seat itself, and not the two that were on
the floor.

4
following a felony conviction.2 He appeals on several grounds;
we will decide the case on the suppression issue.3 “We review
the denial of a motion to suppress for clear error as to the
underlying factual determinations and exercise plenary review
over the application of the law to those facts.” United States v.
Williams, 417 F.3d 373, 376 (3d Cir. 2005).

2
Mosley had a prior felony conviction for burglary, which
supplied the predicate for the § 922(g) charge.
3
Mosley also contends, first, that the evidence of
constructive possession was insufficient; second, that the
District Court erroneously sentenced him under the “armed
career criminal” enhancement provisions of 18 U.S.C. § 924(e);
third, that the District Court failed adequately to determine
whether Mosley’s prior convictions were “related” for purposes
of calculating his criminal history under the Guidelines; and
fourth, that § 924(g), the felon-in-possession statute, is
unconstitutional under the Commerce Clause. As to these, the
government concedes error on the § 924(e) issue, and does not
object to reconsideration of the Guidelines criminal history
calculation. Because we will order suppression of the guns, we
deem it unnecessary to decide the sufficiency question. And we
acknowledge that the Federal Public Defender’s office preserves
the Commerce Clause challenge to § 922(g) in order to pursue
certiorari in the Supreme Court; we are bound by our prior case,
United States v. Singletary, 268 F.3d 196 (3d Cir. 2001), in
which we upheld the constitutionality of the statute.

5
 II.

When one peruses the traffic-stop suppression caselaw,
one is struck by how rarely a traffic stop is found to have been
illegal. In United States v. Whren, 517 U.S. 806 (1996), the
Supreme Court established a bright-line rule that any technical
violation of a traffic code legitimizes a stop, even if the stop is
merely pretext for an investigation of some other crime. And
once a car has been legally stopped, the police may “escalate”
the encounter by visually inspecting the interior of the car, and
checking credentials and asking questions of the occupants. See
United States v. Givan, 320 F.3d 452, 458 (3d Cir. 2003) (“After
a traffic stop that was justified at its inception, an officer who
develops a reasonable, articulable suspicion of criminal activity
may expand the scope of an inquiry beyond the reason for the
stop and detain the vehicle and its occupants for further
investigation.”). Courts give considerable deference to police
officers’ determinations of reasonable suspicion, see, e.g.,
United States v. Nelson 284 F.3d 472, 482 (3d Cir. 2002), and
the cases are steadily increasing the constitutional latitude of the
police to pull over vehicles.4

4
Consider this scenario: the police mount an operation in
which they erect a fake “drug checkpoint” (which are flatly
illegal under Indianapolis v. Edmond, 531 U.S. 32 (2000)) and
then stake out the highway exit just before the fake checkpoint,
videotape all vehicles exiting there, and pull over any vehicle
that violates a traffic law (for example, failing to signal at the
exit turn). The practice was upheld this year in United States v.
Rodriguez-Lopez, 444 F.3d 1020 (8th Cir. 2006). More

6
 Passengers in cars, unlike owners or licensees, have no
reasonable expectation of privacy in the interior of the vehicle
in which they are riding. Because the Fourth Amendment’s
protection against unreasonable searches is predicated on the
invasion by the government of a person’s reasonable expectation
of privacy, passengers are generally held to lack “standing” 5 to
object to evidence discovered in a search of a vehicle. See
Rakas v. Illinois, 439 U.S. 128 (1978). Fourth Amendment
rights are personal rights, and a search of a car does not

famously, in United States v. Arvizu, 534 U.S. 266 (2002), the
Supreme Court reversed the Ninth Circuit’s determination that
a Border Patrol officer had gone too far in basing a traffic stop
of a family van on his observation that the kids had waved at
him “mechanically.”
5
The “standing” inquiry, in the Fourth Amendment
context, is shorthand for the determination of whether a
litigant’s Fourth Amendment rights have been implicated. See
United States v. Kimball, 25 F.3d 1, 5 (1st Cir. 1994) (“We use
the term ‘standing’ as a shorthand method of referring to the
issue of whether the defendant’s own Fourth Amendment
interests were implicated by the challenged governmental action.
‘Technically, the concept of “standing” has not had a place in
Fourth Amendment jurisprudence for more than a decade, since
the Supreme Court in Rakas v. Illinois, 439 U.S. 128, 58 L. Ed.
2d 387, 99 S. Ct. 421 (1978), indicated that matters of standing
in the context of searches and seizures actually involved
substantive Fourth Amendment law.’ United States v. Sanchez,
943 F.2d 110, 113 n.1 (1st Cir. 1991).”).

7
implicate the rights of non-owner passengers: the car is treated
conceptually like a large piece of clothing worn by the driver.

But we should not be distracted by the fact that this case
involves evidence found in a car. This is not an “auto search”
case. The search of the car is not before us; the seizure of
Mosley is. This case is about an illegal seizure by the police of
the defendant, pursuant to which evidence was discovered. The
violation of Mosley’s Fourth Amendment rights was the traffic
stop itself, and it is settled law that a traffic stop is a seizure of
everyone in the stopped vehicle, see Delaware v. Prouse, 440
U.S. 648, 653 (1979).6 Thus passengers in an illegally stopped

6
While the District Court’s opinion is not entirely clear on
this point, we read it to suggest that the District Court
analytically separated the detention of the vehicle from the
removal and detention of Mosley’s person, and believed that
only the latter constituted a seizure of Mosley for Fourth
Amendment purposes. The District Court stated, for example,
that “[f]or purposes of the instant Motion [to suppress], the
Government concedes that the officers violated Defendant’s
Fourth Amendment rights by removing him from the vehicle and
detaining him in connection with the stop of the vehicle.”
The Fourth Amendment violation, however, was the
traffic stop itself, and not just Mosley’s removal from the car.
We wish to reiterate this point for the benefit of future litigants:
a Fourth Amendment seizure of every occupant of a vehicle
occurs the moment that vehicle is pulled over by the police. The
legality of the seizure depends upon the legality of the traffic
stop.

8
vehicle have “standing” to object to the stop,7 and may seek to
suppress the evidentiary fruits of that illegal seizure under the
fruit of the poisonous tree doctrine, as expounded in the line of
cases following Wong Sun v. United States, 371 U.S. 471
(1963). The dispositive legal issue is the causal relationship
between the traffic stop and the discovery of the evidence:
whether the evidence found in the car was “fruit” of the illegal
stop. The question that bedeviled the proceedings below is
whether the evidence found in the car was causally linked to the
illegal seizure of Mosley, the passenger.

In analyzing that causal connection, the District Court
relied on a Tenth Circuit case, United States v. DeLuca, 269
F.3d 1128 (10th Cir. 2001), in which a passenger sought to
suppress evidence found during a traffic stop. Taking its cue
from that case, the District Court proposed various hypotheticals
to test the “factual nexus” between the violation of Mosley’s
Fourth Amendment rights and the discovery of the evidence.
Specifically, the District Court pondered whether, if Mosley had
asked for and received permission to leave the scene
immediately after the car was stopped, the evidence in the car
would still have been discovered. Since the answer to that

7
For the most comprehensive collection of cases, see 6
Wayne R. LaFave, Search and Seizure § 11.3 (4th ed. 2004)
(citing, inter alia, United States v. Grant, 349 F.3d 192 (5th Cir.
2003); United States v. Ameling, 328 F.3d 443 (8th Cir. 2003);
United States v. Gama-Bastidas, 142 F.3d 1233 (10th Cir.
1998); United States v. Sowers, 136 F.3d 24 (1st Cir. 1998);
United States v. Rusher, 966 F.2d 868 (4th Cir. 1992)).

9
question is obviously “yes,” the District Court ruled that Mosley
had failed to demonstrate an adequate “factual nexus” between
the illegal government action and the discovery of the
challenged evidence. Although the government had clearly
violated Mosley’s Fourth Amendment rights, the District Court
determined that the specific violation of Mosley’s rights – as
opposed to Hayes’ rights – did not have a sufficiently close
causal connection, or “factual nexus,” to the discovery of the
evidence to support Mosley’s suppression claim.

The general requirement of a “factual nexus” between a
specific Fourth Amendment violation and a specific piece of
evidence derives from two Supreme Court cases on wiretap
evidence. In those cases, the government had gathered
thousands of discrete pieces of evidence over many months of
investigation. Over the course of the investigation, the
government committed various illegal acts, and the question for
the Court was how to determine which pieces of evidence were
tainted by the particular illegal actions. See United States v.
Nardone, 308 U.S. 338, 341 (1939); United States v. Alderman,
394 U.S. 165, 183 (1969). Because of the multiplicity and
complexity of the investigation and the evidence, there was no
commonsense causal relationship between any given Fourth
Amendment violation and any given piece of evidence. Rather
than hold all the evidence to have been tainted by the violations,
the Court held that the proper course is for district courts to
probe more deeply, and employ thought experiments to
determine which violation was causally connected to which

10
piece of evidence.8 These cases express the commonsense
proposition that a single Fourth Amendment violation does not
taint an entire case, but only the evidence uncovered as a result
of that violation.

Prior to DeLuca, courts had not generally thought that
traffic stops presented sufficiently complex investigatory
contexts to warrant such an added layer of causal analysis. In
DeLuca, however, a panel of the Tenth Circuit, over a heated
dissent by former Chief Judge Seymour, applied that
counterfactual – “What if?” – approach to a suppression motion
brought by a passenger who was illegally detained during a
traffic stop. The application of “factual nexus” hypotheticals to
a traffic stop suppression case was a novel idea. The majority
view in the circuits was and remains that in a traffic stop, there
will always be a sufficient “nexus” between the stop and the
search, unless there are significant intervening events that sever
or attenuate the causal chain. There is generally no “nexus”
problem in illegal traffic stop cases, as the leading treatise puts
it, because the connection between the illegal action and the
discovery of the evidence is straightforward: If the police had
not pulled over the vehicle, they would not have discovered the
evidence. See 6 Wayne R. LaFave, Search and Seizure
§ 11.4(d) (4th ed. 2004) (summarizing caselaw).

8
The test has since been applied by the Ninth Circuit in
complex cases involving ongoing police investigations. See,
e.g., United States v. Kandik, 633 F.2d 1334 (9th Cir. 1980);
United States v. Allard, 600 F.2d 1301 (9th Cir. 1979); United
States v. Cella, 568 F.2d 1266 (9th Cir. 1977).

11
 We can understand why the DeLuca majority thought that
the case required some revision to the traditional fruits analytical
apparatus. DeLuca did not involve an illegal traffic stop. It
involved instead a legal traffic stop that became illegal when the
police continued to detain the vehicle and its occupants after the
legitimate purposes of the stop had been completed. 9 Because
the stop itself was legal, the court reasoned that whatever
government actions violated the defendant’s rights must be
analytically separable from the traffic stop. The Fourth
Amendment violation in DeLuca was the detention of the
defendant passenger, along with the other occupants of the car,
beyond the period necessary to complete the legitimate purposes
of the stop. But at the point that the detention of the defendant
passenger became illegal, the police already had control over the
vehicle. The court therefore tried to tease out the causal efficacy
of the precise illegality raised by the defendant passenger. The
court asked whether, if the passenger had been allowed to leave
the scene before the detention became illegal, the incriminating

9
In fact this is not such an unusual occurrence. A traffic
stop requires only reasonable suspicion to believe that a traffic
violation has been committed. But detaining the vehicle longer
than is necessary to effectuate the legitimate response to that
traffic violation requires independent suspicion that some other
crime is afoot. The transition from traffic stop to investigatory
stop is the focal point of many suppression cases. See, e.g.,
Illinois v. Caballes, 543 U.S. 405, 407 (U.S. 2005) (“A seizure
that is justified solely by the interest in issuing a warning ticket
to the driver can become unlawful if it is prolonged beyond the
time reasonably required to complete that mission.”).

12
evidence would still have been discovered. The answer was
“yes”: it wasn’t his car, so his leaving would not have removed
the evidence.

The question in DeLuca was thus whether the police
would still have discovered the challenged evidence if they had
let the passenger go before doing anything illegal to him. On
the DeLuca facts, if the police had let the passenger go after the
initial legal stop but before the subsequent illegal prolongation
of the stop, then nothing illegal would have been done to him –
and the evidence would still have been discovered. Therefore
the passenger had no suppression claim. So reasoned the Tenth
Circuit.10

But we agree with Mosley that DeLuca is inapposite here.
The hypothetical, and the holding, are relevant only to situations
in which the initial traffic stop is legal, and that is not our case.
We express no opinion on the viability in this Circuit of the
DeLuca test on DeLuca facts; we decide the case before us, not

10
Even on its limited facts, DeLuca was not
uncontroversial. Former Chief Judge Seymour issued a
blistering dissent, calling the majority’s reasoning “ludicrous,”
and Professor LaFave concurred in that assessment. The most
serious criticism is that the counterfactual methodology “forces
the defendant to disprove inevitable discovery and does an end
run around the government’s burden of proof on inevitable
discovery.” DeLuca, at 269 F.3d at 1145 n.1 (Seymour, J.,
dissenting).

13
a different one.11 But whatever its viability on appropriate facts,
this case does not present such facts. If the initial traffic stop is
illegal, then even if the passenger is allowed to leave the scene
before the search, it will not be the case that the police have not
violated his Fourth Amendment rights. Where the traffic stop
itself is illegal, it is simply impossible for the police to obtain
the challenged evidence without violating the passenger’s
Fourth Amendment rights. DeLuca says nothing about such
situations.

The Tenth Circuit itself has addressed the question
whether DeLuca applies to traffic stops illegal from their
inception, and stated clearly that it does not. It applies, the court
explained in a recent suppression case applying DeLuca, only to
cases in which the illegal police conduct occurred after the

11
We will not be overly coy, though: we recognize that
the rationale for our holding might be thought to undermine the
DeLuca rationale even on DeLuca facts. But the preceding
sentence is dicta; when an appropriate case arises, the parties
may do what they will with our decision here.

14
police had legally gained control of the vehicle.12 The temporal
sequence of events makes all the difference, said the court:

[Wong Sun] and its progeny, see, e.g., United
States v. Melendez-Garcia, 28 F.3d 1046,
1053-54 (10th Cir. 1994), are readily
distinguishable insofar as in those cases the illegal
police conduct preceded the means by which the
evidence was obtained, thus establishing the
requisite factual nexus between the evidence and
the illegal conduct. By contrast, any unlawful
police activity here occurred after voluntary
consent had been obtained. Consequently, [the
defendant] could not establish that, but for the
alleged illegal seizure, the evidence would not
have come to light as required by DeLuca.

12
And the same is true of an earlier Tenth Circuit case,
United States v. Nava-Ramirez, 210 F.3d 1128 (10th Cir. 2000),
cited in DeLuca: “Nava-Ramirez does not contest the legality
of the initial stop. Rather, he argues that at the moment [the
officer] concluded his search of the passenger compartment
without finding any evidence indicating Nava-Ramirez was
involved in illegal activity, his continued detention became
unlawful.” That factual setting – initially legal stop, subsequent
illegal detention of passenger – is the underpinning and
necessary condition for the DeLuca-type “factual nexus” test.
It has absolutely no application to situations where the passenger
challenges the legality of the initial stop.

15
United States v. Roberts, 91 Fed. Appx. 645, 648 (10th Cir.
2004) (emphasis added).

The District Court’s application of DeLuca to the case at
bar, in which the illegal police conduct preceded the means by
which the evidence was obtained, was error, because even under
the Tenth Circuit’s heightened “factual nexus” test, such a
temporal scenario would appear to clearly supply the requisite
“factual nexus.” 13

It is clear, so far, that an illegal traffic stop constitutes a
seizure of all occupants of a vehicle, including passengers, and
that whatever the utility of the DeLuca counterfactual analysis
to fact patterns not before us, it is not the proper analytical
model for the case that is before us.

13
The Roberts case, to be sure, is unpublished, but we
think the recently adopted amendment to Fed. R. App. Proc.
32(a) confirms the utility of looking to unpublished cases to
determine how precedential cases are applied. Where, as here,
an NPO clarifies the application of a prior precedent, almost all
the circuits allow its citation by the parties, and we will not
needlessly deprive ourselves of useful guidance on the scope of
the caselaw that governed this case below.

16
 III.

A.

Fourth Amendment rights are personal rights. That
proposition is not in dispute. The problem is that from that
proposition, the result in any particular case is not always
immediately obvious. Mosley does not dispute that he had no
personal expectation of privacy in the interior of the car; the
government does not dispute that he did have a reasonable
expectation that he would not be seized without probable cause.
The problem is whether the evidence in this case was discovered
as a result of his seizure.

As we will detail below, most courts treat evidence found
during an illegal traffic stop as the fruits of that stop, and see no
conceptual difficulties in suppressing such evidence when
introduced against passengers. Our most recent decision to face
such a scenario, United States v. Williams, 413 F.3d 347 (3d Cir.
2005), concerned a non-owner passenger in a parked van that
was approached by two police officers, who subsequently
observed contraband in the vehicle. The defendant claimed that
the approach constituted a seizure. We framed the suppression
issue as follows:

The central issue on appeal . . . is whether
Williams was seized within the meaning of the
Fourth Amendment when the police . . .
approached the van. If Williams was “seized” by
the police when they approached the parked van
without probable cause or reasonable suspicion to

17
 do so, then the District Court correctly suppressed
all evidence obtained in connection with the
ensuing arrest under the “fruits of the poisonous
tree” doctrine.

413 F.3d at 351. Our approach can be summarized as follows:
We ask, first, whether there was a seizure. If so, then we ask
whether there was reasonable suspicion or probable cause. If
not, then suppression is proper unless the government can show
that the taint was purged. We did not even comment in Williams
on the “causal nexus” between the alleged seizure and the
discovery of evidence; on these facts we took that nexus to be
self-evident.

However, the quoted passage is dicta because we held
both that the approach was not a seizure and that the officers had
reasonable suspicion sufficient for a Terry stop in any event.
The vehicle was parked in a public place and the officers did not
make a show of force, and “law enforcement officers do not
violate the Fourth Amendment’s prohibition of unreasonable
seizures merely by approaching individuals on the street or in
other public places.” Id. at 352 (quoting United States v.
Drayton, 536 U.S. 194, 200 (2002)).

Though dicta, the analytical approach suggested by
Williams is consistent with the approach proposed by the leading
Fourth Amendment treatise.

In the typical case in which an illegal arrest is
followed by a search no “fruits” problem of any
magnitude is presented. . . . This is direct rather

18
 than derivative evidence, and there is no occasion
to be concerned about the limits of the fruit of the
poisonous tree doctrine. . . . Problems of this kind
arise in the context of passengers in vehicles
attempting to have evidence found therein
suppressed . . . . [T]he passenger will claim that
the subsequent discovery of the evidence in the
vehicle was a fruit of his prior illegal detention.
It is very often the case that such a connection is
readily made out when the initial stopping of the
vehicle (and thus all of the occupants) was illegal.

6 LaFave, supra, § 11.4(d) (emphasis added).

We have not, however, yet had occasion to decide a case
requiring a precise articulation of the application of the fruit of
the poisonous tree doctrine to evidence found during illegal
traffic stops when introduced against vehicle passengers. We
will therefore state the theoretical issue as perspicuously as we
can: Is an illegal traffic stop of a car occupied by a driver and
a passenger a single constitutional violation, with two victims,
each of whom can seek to suppress all fruits of that violation?
Or is it analytically separable into two individual constitutional
violations, each with one victim, each of whom may seek to
suppress only the fruits of the violation of his individual right?
Today we endorse the former proposition, but as we
acknowledge the logical appeal of the latter proposition, we will
set out the best arguments in its favor, and then explain why we
are rejecting them.

19
 1.

The “analytic separation” position, the position we are
rejecting, can be defended both on logical grounds and via a
reductio ad absurdum. Here are the logical grounds. Because
Fourth Amendment rights are personal rights, when the police
pull over a car with a driver and a non-owner passenger, two
individual seizures occur simultaneously: seizure of the driver,
and seizure of the passenger.14 Thus, we should not see the
traffic stop as one discrete constitutional violation (with two
victims), but rather as two separate constitutional violations
(each with one victim). Because fruits analysis always proceeds
from the specific constitutional violation inflicted on the
defendant, this analytic separation of violations necessitates a
concomitant separation of the respective fruits suppression
analyses. Because the violation of the passenger’s constitutional
rights was the seizure of the passenger (analytically separated
from the seizure of the driver), we must ask, in any fruits
analysis, whether the challenged evidence was seized as a causal
result of the seizure of the passenger. To get at the interior of
the car, where the evidence is located, the police must perforce
seize the driver and the passenger, by stopping the car. But that
one act constitutes two separate seizures. The passenger was not
in control of the car, so it is the seizure of the driver, and not the
passenger, that is required in order for the police to obtain
control over the car. The passenger’s presence has no effect on

14
Actually three seizures occur, because the car itself is
also seized. But only the personal seizures are relevant to the
argument.

20
the ability of the police to seize the driver and control the car.
Thus the evidence in the car would be found whether or not the
passenger was present in the car at all. Seizure of the passenger
is, accordingly, logically ancillary to the search of the vehicle.
It is logically necessary only for a search of the passenger’s
person. On this view, therefore, evidence found in the car, but
not on the passenger’s person, cannot be suppressed by the
passenger, even though the seizure of the passenger was
unconstitutional.

Some simple hypotheticals bring out the force of this
argument. Suppose that the car stops and X, a passenger, gets
out at the corner. Just as the car begins to pull away, the police,
acting on an anonymous tip, roar up and stop the car,
simultaneously ordering X, on the sidewalk, to freeze. Evidence
is found in the car but is suppressed as to the driver because the
stop was illegal. It is then introduced against X. May X
suppress? Certainly not. The two seizures are clearly separate
causal events for Fourth Amendment purposes. Nor can X
challenge a search of the car, no matter how illegal, because he
has no privacy interest in the car.

Now put X back in the car. What is the legal significance
of that change of place? The most obvious difference is that it
becomes physically impossible for the police to stop the car (and
detain the driver) without also seizing and detaining X. But X’s
legal situation with respect to the car and driver remains the
same: as a passenger, his privacy interest in the interior of the
car is precisely what it was when he was standing on the
sidewalk – zero. Thus, just as X’s seizure on the sidewalk
cannot logically or legally have been a cause of the discovery of

21
evidence inside the car, neither can his seizure while inside the
car as a passenger be a logical or legal cause of the discovery of
evidence inside the car.

The discovery of evidence inside a car simply cannot be
a violation of a passenger’s Fourth Amendment rights,
according to this argument. The passenger has a personal right
not to be seized, and that right is violated when the car is
illegally pulled over. But the illegal seizure of the passenger’s
person cannot be a legal cause of the discovery of evidence that
is not on the passenger’s person. The police may have
performed both acts at the same time, but because there was no
logical connection between the two the illegal seizure was not
a but-for cause of the discovery of the evidence.

2.

Here is the reductio ad absurdum. It is settled law that if
the police illegally enter a house and search it, the owner or
tenant of the house, or any long-term guests, may suppress
evidence found during the search.15 Short-term guests, however,
have no expectation of privacy in the house and therefore cannot
suppress the fruits of the illegal search. This is true even if the
short-term guests were seized pursuant to the illegal entry into
the house. If, for example, the police barricaded the exits to a

15
Unless, of course, the illegality is restricted to a
violation of the knock-and-announce rule, in which case no one,
not even the owner, can suppress. See Hudson v. Michigan, 547
U.S. --- (2006).

22
residence, entered, and ordered everyone present to freeze, they
would have thereby seized everyone present in the residence. If
their entry was illegal, for example if effected without a warrant
and absent exigent circumstances, then all of those seizures were
illegal. However, only the owner, tenant, or long-term guests
could suppress evidence found during the search. Short-term
guests would face the full evidentiary weight of any evidence
discovered. See Minnesota v. Olson, 495 U.S. 91 (1990).

Now make the house a mobile home, and drive it down
the street until it is pulled over illegally. The police again
illegally seize all the occupants and search the interior. Under
the holding we are announcing today – which conforms, as we
observed above, with those of our sister circuits – those short-
term guests are now passengers in an illegally seized vehicle,
and thus can suppress all evidence discovered during the search.
This result appears anomalous insofar as the Fourth Amendment
has been repeatedly characterized by the Supreme Court as
affording enhanced protection to the home, and diminished
protection to vehicles. Compare, e.g., Georgia v. Randolph, 547
U.S. --- (2006), slip op. at 10 (citing Wilson v. Layne, 526 U. S.
603, 610 (1999) (invoking the “centuries-old principle of respect
for the privacy of the home”); Minnesota v. Carter, 525 U.S. 83,
99 (1998) (Kennedy, J., concurring) (“[I]t is beyond dispute that
the home is entitled to special protection as the center of the
private lives of our people.”); Miller v. United States, 357 U.S.
301, 307 (1958) (noting common law tradition that a poor man
in a humble cottage might nonetheless bid defiance to all the
forces of the crown (if it is his cottage)), with, e.g., United States
v. Martinez-Fuerte, 428 U.S. 543, 561 (1976) (explaining that
Fourth Amendment protections are lessened for occupants of

23
cars because cars searches do not implicate “the sanctity of
private dwellings, ordinarily afforded the most stringent Fourth
Amendment protection.”). Yet in our hypothetical, passengers
in a vehicle are afforded greater Fourth Amendment protection
than guests in a home.

B.

We have set out a coherent logical argument for an
analytic separation rule, and highlighted an apparently
anomalous contrast between vehicle and home seizure cases that
rejection of that rule might seem to entail. But we are not
persuaded. We will respond to the argument in two ways. First,
in Part III.B, we will survey the caselaw of our sister circuits, all
of which uphold passenger suppression claims following illegal
stops. Second, in Part III.C, we will reject the apparent logical
plausibility of the analytic separation argument as inconsistent
with the more pragmatic methodology exemplified by the
Supreme Court’s exclusionary rule jurisprudence.

1.

The Ninth and Eleventh Circuits have recently decided
cases with precisely analogous facts. See United States v.
Twilley, 222 F.3d 1092 (9th Cir. 2000); United States v.
Chanthasouxat, 342 F.3d 1271 (11th Cir. 2003). In each case,
the traffic stop was illegal from its inception,16 and evidence

16
The illegality of the traffic stop was caused in each case
by a mistake of law on the part of the police officer. (Unlike a

24
found during the traffic stop was introduced against a passenger
in the car. In each case, the government contested the
passenger’s motion to suppress by arguing that the passenger
lacked “standing” to challenge the evidence because he did not
have a reasonable expectation of privacy in the interior of the
car. In each case, the court applied a standard fruits analysis,
and suppressed the evidence as the fruit of the illegal seizure.17

The two courts treated this fact pattern as an utterly
straightforward and unremarkable application of the fruit of the
poisonous tree doctrine. Their analyses proceed precisely as
Mosley argues ours should, in the following three steps. First,
the traffic stop was a violation of the defendant’s Fourth

reasonable mistake of fact, a mistake of law negates reasonable
suspicion and renders the stop illegal.) In Twilley, the officer
pulled over the car based on the California law that all vehicles
must display all plates issued by the state of registration. The
car was from Michigan, which issues only one plate. The
officer assumed that Michigan must issue two because, he said,
“an awful lot of states issue two plates.” 222 F.3d at 1094. In
Chanthasouxat, the officer pulled over the van because it lacked
an inside rearview mirror, and he thought that Alabama law
required one. It does not.
17
Indeed, both courts made the distinction between the
seizure of the passenger effected by the stop, and the subsequent
search of the car, noting that were the search the only grounds
for suppression, the passenger would lack “standing.”
Chanthasouxat, 342 F.3d at 1273 n.1; Twilley, 222 F.3d at 1095.

25
Amendment rights; second, the evidence was found as a direct
consequence of the stop (that is, there were no significant
intervening events); third, the government did not establish any
of the various available exceptions (attenuation, independent
source, inevitable discovery). The Twilley court held that
“[b]ecause we conclude that the stop was not supported by
reasonable suspicion, and because the subsequent search was a
product of the stop, the evidence leading to Twilley’s conviction
should have been suppressed.” Id. at 1097.18 The
Chanthasouxat court held that “[b]ecause we conclude that the
initial traffic stop violated the Fourth Amendment, the violation
was not cured by voluntary consent, and that Chanthasouxat’s
[incriminating] statements [made during the stop] were fruits of
the poisonous tree, we hold that the drug evidence and
Chanthasouxat’s statements must be suppressed.” 342 F.3d at
1281.

18
The parties give a fair amount of attention to United
States v. Pulliam, 405 F.3d 782 (9th Cir. 2005), but Pulliam is
inapposite for the same reason most of the apparently analogous
cases are: there was no determination or allegation that the
initial stop of the car was illegal. The defendant in Pulliam was
convicted based on evidence found in a search of a car in which
he was a passenger, but he challenged only his personal arrest
and search – not the initial traffic stop. He conceded that the
traffic stop was legally justified, because the car had a broken
tail light. 405 F. 3d at 785. Pulliam is just another of the many
cases where passengers lose suppression motions following
legal traffic stops. That is not our case.

26
 What is noteworthy about these cases is that they include
no discussion whatsoever of the “factual nexus” between the
illegal stop and the discovery of the evidence. The courts see
the chain of events between the illegal stop and the subsequent
discovery of evidence to constitute such a self-evidently close
“factual nexus” that, as Professor LaFave puts it, see 6 LaFave,
supra, § 11.4(d), there is no need to probe the limits of the fruit
of the poisonous tree doctrine.19

19
See also, e.g., United States v. Colin, 314 F.3d 439 (9th
Cir. 2002) (same analysis as Twilley, and collecting cases). In
both Twilley and Chanthasouxat, indeed, (and unlike our case)
the driver of the vehicle in fact consented to the search, but the
court ruled that the consent was not “obtained by means
sufficiently distinguishable from the illegal stop to be purged of
the primary taint.” Chanthasouxat, 342 F.3d at 1280 (internal
quotes, brackets omitted); accord Twilley, 222 F.3d at 1097
(because “the interrogation and search were a direct result of the
illegal stop . . . this is a classic case of obtaining evidence
through the exploitation of an illegal stop.”) (internal quotes
omitted).
Consent following an illegal seizure does not in itself
purge the taint of the illegality for Fourth Amendment purposes;
the government must show sufficient attenuation to causally
disconnect the consent from the seizure. See United States v.
Snype, 441 F.3d 119, 133 (2d Cir. 2006) (collecting numerous
cases).

27
 2.

In United States v. Reed, 349 F.3d 457 (7th Cir. 2003),
the defendant passenger confessed to drug distribution after
spending several hours with police (whether in custody or not
was disputed) following a traffic stop. He contended that the
police lacked probable cause for the stop,20 and sought
suppression of the confession on fruits grounds. The district
court ruled that even if the arrest was illegal, his subsequent
confession was still voluntary. Thus the district court did not
rule on the legality of the initial stop. On appeal, the Seventh
Circuit, applying Brown v. Illinois, 422 U.S. 590 (1975), vacated
and remanded, holding that, notwithstanding the lapse of time
and the voluntariness of Reed’s confession, the confession
would have to be suppressed as fruit of the poisonous tree if the
initial stop had been illegal. The Reed court explicitly rejected
a “counterfactual purgation” analysis of the sort employed by
the Tenth Circuit in DeLuca and by the District Court in the case
at bar:

The dissent opines that Reed would have
confessed even if he had been allowed to go home

20
The police officer pulled over the truck in which Reed
was a passenger because it was towing a horse trailer, and, the
officer testified, horse trailers are sometimes used to transport
marijuana because the smell of the horses masks the smell of the
drugs. In fact, the trailer contained horses and cash, but not
drugs. In the disputed confession, Reed admitted having been
part of a separate distribution conspiracy. 349 F.3d at 462.

28
 rather than being held for hours, because his
confession stemmed from a desire to win favor
and reward and was not a consequence of the
illegality. We cannot make that determination as
a matter of law, and the government has the
burden to prove that his confession was
attributable to a factor other than the prolonged
detention following the allegedly illegal arrest.
That Reed determined that it was in his best
interest to cooperate does not somehow divorce
his decision from the unlawful detention.

Reed, 349 F.3d at 466.

The Reed court rejects both components of the DeLuca
counterfactual analysis: first, the shifting of the explanatory
burden to the defendant, and second, the artificial “divorcing”
of the (legal) act by which the evidence was physically obtained
from its (illegal) necessary causal antecedent. If that divorce is
going to occur, the court insists, it will be through the standard
fruits exceptions, and they must be shown by the government.

3.

In United States v. Guevera-Martinez, 262 F.3d 751 (8th
Cir. 2001), the defendant was a passenger in a car pulled over in
an illegal traffic stop. During the stop, the officers searched the
car and discovered methamphetamine. On that basis they
arrested Guevera-Martinez. That night, in jail, he told an INS
agent that he was in the country illegally. Guevera-Martinez
was charged in separate indictments with both drug and

29
immigration violations. Guevera moved to suppress the drugs,
arguing that the traffic stop was illegal. The district court
granted the motion, and the drug charges were dismissed. On
the immigration charge, Guervera-Martinez sought to suppress
both the statements he made and the fingerprints taken while he
was in jail. The district court granted the suppression motion on
the same grounds, holding that both the statements and prints
were fruit of the illegal traffic stop, and the Eighth Circuit
affirmed.

The Eighth Circuit applied a straightforward fruits
analysis: “[O]fficers obtained Guevera-Martinez’s fingerprints
[and statements] by exploiting his unlawful detention, instead of
by means sufficient to have purged the taint of the initial
illegality.” Id. at 755. The court deemed it irrelevant that
Guevera-Martinez “will inevitably face” civil deportation
proceedings in which new fingerprint evidence would easily be
obtained, and which would support the reinstatement of the
criminal immigration charges: “[T]he government asks us to
ignore its use of tainted evidence in this case. We decline to [do
so] . . . The important thing is that those administering the
criminal law understand that they must obtain the evidence the
right way.” Id. at 756 (quoting Davis v. Mississippi, 394 U.S.
721, 726 n.4 (1969) (internal quotes, brackets omitted).

4.

United States v. Dortch, 199 F.3d 193 (5th Cir. 1999), is
also very close in its facts to the case at bar. In Dortch, the
defendant was the driver rather than a passenger, but this
difference is irrelevant because Dortch’s suppression claim was

30
based solely on the detention itself. Dortch was stopped for a
traffic infraction, and he did not challenge the legality of the
stop. However, the police continued to detain him (and,
obviously, his vehicle) after the legitimate purpose of the traffic
stop had been completed. Id. at 197. Instead of allowing him to
leave, the police detained him for fifteen minutes while they
summoned a drug-sniffing dog team.

The bulk of the Fifth Circuit’s analysis is devoted to the
question of whether Dortch’s continued detention, once the
purposes of the traffic stop had been completed, was legal. The
court concluded that it was not – that the police had no probable
cause to continue to detain him. The government argued that
Dortch consented to the subsequent search once the dog team
arrived, but the court held that even if he did consent, the
evidence must still be suppressed: “even if Dortch’s consent
was voluntarily given . . . the consent was not valid. Instead,
because the causal chain between the illegal detention and
Dortch’s consent . . . was not broken, the search was
nonconsensual.” Id. at 202.

The court thus ordered suppression of all the evidence –
which was considerable – that had been amassed against Dortch,
and remanded not just for retrial, but with the specific order that
he be granted a judgment of acquittal. The justification was
straightforward fruits analysis: the moment the legal purposes of
the traffic stop were satisfied, any further detention of Dortch
was illegal. When the dog team arrived, the dogs were sent
around the car and alerted to it. On that basis, the police
searched the car and found drugs. And on that basis they

31
secured a warrant for Dortch’s home, searched it and found
more drugs and paraphernalia.

The Dortch case is particularly significant as an analogue
to the case at bar because it was governed by the twin
propositions that, first, an exterior investigation of a car by a
drug-sniffing police dog is not a search as a matter of law, see
Dortch, 199 F.3d at 198; (citing United States v. Seals, 987 F.2d
1102, 1106 (5th Cir. 1993)); see also Illinois v. Caballes, 543
U.S. 405, 409 (2005), and second, that the dog’s alerting to the
car constitutes probable cause for a search, as a matter of law.
See Dortch, 199 F.3d at 198 (citing United States v. Zucco, 71
F.3d 188, 191-92 (5th Cir. 1995). Thus, in Dortch’s case, as in
Mosley’s, there was no search to which he can object. If the dog
team had arrived while Dortch was legally detained, there would
have been no Fourth Amendment violation.21 The only basis for

21
And indeed Dortch was neither the owner nor the
authorized possessor of the car. The car had been rented by a
third party (neither Dortch nor the passenger). Thus there is a
colorable argument that Dortch had no reasonable expectation
of privacy in the interior of the car whatsoever. But the court
explains that it does not need to reach that issue, because the
detention was illegal, and the fruits suppression follows directly
from that determination. See Dortch, 199 F.3d at 197-98 and
n.4 (“Given that Dortch does not challenge the legality of the
search, it is puzzling that the dissent goes to such efforts to
develop its theory that ‘because the rental agreement provided
only the renter was an authorized driver, Dortch had no right to
complain of the vehicle’s detention.’ In arguing that Dortch has

32
Dortch’s suppression motion, as for Mosley’s, is that the
challenged evidence is the fruit of an illegal detention. Thus it
is irrelevant that Dortch was the driver rather than a passenger,
because that distinction applies only to challenges to the search
of the car, and Dortch, like Mosley, made no such challenge.

United States v. Jones, 234 F.3d 234 (5th Cir. 2000), is
similar to Dortch. In Jones, the car was validly stopped for
speeding, but the police continued to detain both driver and
passenger without probable cause after the legitimate purposes
of the stop – issuance of a citation, and computer criminal
history check – were completed. During the illegal prolongation
of the detention, the driver consented to a search of the car, and
contraband was discovered. The Fifth Circuit, upon determining
that the consent was not sufficiently attenuated from the illegal
detention to have been purged, ordered suppression of the
evidence as to both the driver and the passenger, reasoning that
although the passenger had no standing to challenge the search
of the car, he could challenge the illegal extension of the traffic
stop, and that extension was a single event which was causally
connected to the discovery of the evidence. Id. at 244.

Dortch and Jones suggest very strongly that had Mosley’s
case arisen in the Fifth Circuit, the gun would be suppressed. In
Dortch, just as here, there was no invasion of the defendant’s

no legitimate privacy interest in a rental car, the dissent seems
to miss the point. As we explain above, Dortch’s complaint is
not that the vehicle was detained or improperly searched, but
rather that he was improperly seized . . . .”).

33
reasonable expectation of privacy in the search that produced
the evidence. The invasion came solely in the detention (seizure
of the person), and the court applied a straightforward fruits
analysis, pursuant to which it took it as self-evident that a car
search following an illegal traffic stop is the fruit of that stop.

5.

In United States v. Kimball, 25 F.3d 1 (1st Cir. 1994), the
defendant was a passenger in a car that was stopped by the
police. All three occupants were arrested on suspicion of
burglary, and the police performed an “inventory” search of the
car upon towing it to the station. Kimball sought to suppress
evidence recovered from the car, and the court framed the issue
as follows:

A police officer’s act of stopping a vehicle
and detaining its occupants constitutes a seizure
within the meaning of the Fourth Amendment. . . .
When a police officer effects an investigatory stop
of a vehicle, all occupants of that vehicle are
subjected to a seizure, as defined by the Fourth
Amendment. The fact that a defendant is a
passenger in a vehicle as opposed to the driver is
a distinction of no consequence in this context.
The interest in freedom of movement and the
interest in being free from fear and surprise are
personal to all occupants of the vehicle, and an
individual’s interest is not diminished simply
because he is a passenger as opposed to the driver
when the stop occurred. . . . Thus, if the initial

34
 stop of the vehicle was illegal, evidence seized by
virtue of that stop, such as the tools in this
instance, may be subject to exclusion under the
“fruit of the poisonous tree” doctrine.

Kimball, 25 F.3d at 5-6 (citations omitted).

The court then added, in a very significant footnote:

The Government’s reliance on Rakas v. Illinois, in
the context of a stop, is misplaced. In Rakas, the
United States Supreme Court held that a mere
passenger in an automobile ordinarily does not
have the legitimate expectation of privacy
necessary to challenge the search of that
automobile. The Supreme Court’s decision,
however, was limited to the issue of whether the
passenger’s legitimate expectation of privacy was
invaded by a search of the vehicle, and not the
stop thereof.

Id. at 6 n.3 (emphasis added, internal cites omitted).

The footnote is significant because it helps to clarify what
we think was a source of confusion in the proceedings below.
Rakas held simply that a passenger in a car has no reasonable
expectation of privacy in the interior of the car, and thus that a
search of that car does not violate any of the passenger’s Fourth
Amendment rights. But Rakas says absolutely nothing about the
scope of the exclusionary rule with respect to the fruits of an
illegal stop. The Kimball court makes it clear that the

35
passenger’s reasonable expectation of privacy vis-a-vis the
search is completely irrelevant to the fruits inquiry with respect
to the stop.

We read Kimball as holding that the determinative
question in passenger suppression is the legality of the stop: if
the stop is illegal, then standard fruits suppression will apply.22

22
The court ultimately affirmed the denial of Kimball’s
suppression motion on the grounds that the stop was reasonable.
25 F.3d at 8.
For an illustration of this methodology in practice in the
district courts, see United States v. Jones, 374 F. Supp. 2d 143
(D.D.C. 2005), which is very strongly analogous to our facts.
The district court suppressed all the challenged evidence against
the defendant after going through precisely the fruits analysis
Mosley contends for here. Jones was a non-owner passenger in
a vehicle that was illegally detained by the police. The car was
parked when officers approached, questioned, detained, and
arrested the two occupants, effecting an illegal seizure of Jones.
The government argued first that the encounter was consensual,
and then in the alternative that it was a permissible Terry stop.
The court rejected both arguments and found the detention to be
illegal. Id. at 149, 152. Accordingly, it suppressed all evidence
subsequently recovered, including both physical evidence and
statements, because “the government failed to meet its burden
of justifying under the Fourth Amendment the police intrusion
upon Jones’ liberty.” Id. at 153. The court recognized that
Jones, as a non-owner passenger, “failed to demonstrate a
legitimate expectation of privacy in the vehicle or items

36
 6.

The government brings to our attention United States v.
Carter, 14 F.3d 1150 (6th Cir. 1994), a case in which evidence
found during a search of a vehicle was suppressed as to the
driver but admitted as to the passenger. Carter was a passenger
in a van, which the police pulled over for failure to have a valid
license plate. The crucial factual and procedural point, which
makes Carter inapposite, is that Carter did not challenge the
legality of the initial stop. Thus Carter, like DeLuca, cannot
guide the analysis in our case, because unlike in our case, the
court did not find that the initial traffic stop itself was illegal:

[W]hether or not the original traffic stop was
unconstitutional – an issue that was not preserved
in Carter’s objection to the magistrate’s report and
that we do not reach here – we shall assume for

recovered from it,” id. at 154, but deemed that fact irrelevant
because the suppression claim was grounded in the illegal
detention rather than the search itself. “[The auto passenger
search cases] involve claims that the search of the vehicle or
compartments within it was unlawful. By contrast, Jones here
argues that he was unlawfully stopped and seized, and thus the
contents of the [car] should be suppressed as the result of that
unlawful seizure.” Id. The court accordingly considered
whether any “dissipating” or “purging” factors were present,
such as lapse of time or intervening circumstances. Finding
none, the court ordered all evidence recovered as a result of the
initial encounter to be suppressed.

37
 purposes of analysis, not only that the subsequent
arrest of the driver was unconstitutional, but also
that the detention of Mr. Carter, if not illegal from
the outset, became illegal when the driver was
arrested.

Carter, 14 F.3d at 1154.

Note that the court does not hold that Carter’s
suppression motion would fail even if the initial traffic stop had
been illegal. The court does not assume that the initial stop was
illegal, but only that Carter’s detention “became illegal when the
driver was arrested.” That distinction (carefully preserved by
the “if not” construction) makes all the difference. As long as
the police initially obtained control over the vehicle legally, then
(on the DeLuca reasoning) no search of the vehicle after that
point, no matter how unconstitutional, will be subject to
challenge by a passenger. But Carter does not address the
situation in which the initial stop was illegal; to so treat it is to
stretch its holding not only beyond its facts but beyond its
language.

C.

As the preceding survey establishes, the prevailing rule
in the courts of appeals is that an illegal traffic stop entails a
suppression remedy for all occupants of the car. The authority
of our sister circuits is persuasive. However, we think the
interests of justice and jurisprudential clarity are best served by
giving this issue the fullest possible airing, so we think it
incumbent on us to rebut the logical argument for analytic

38
separation we presented above. We think that argument is
rebuttable independently of the persuasive weight of our sister
circuits’ decisions, for the following reasons.

First, we do not think it quite so self-evident that the
seizure of a passenger in a vehicle is not a but-for cause of the
discovery of evidence in the vehicle. The simplest statement of
the concept of but-for causation is that event A is a but-for cause
of event B if event B could not happen without event A
happening first. But-for causation is an inference drawn from
regularly observed correlation.

But it must be stressed that causation is an inference, not
an observation, as philosophers since at least Hume have
reminded us. The only empirical facts that we can discover
about the world are facts about correlation. We cannot observe
causal relationships, whether of cue ball to eight ball, of moon
to tides, or of diet-pill ingestion to heart failure. What we
observe is correlation, and when we see it regularly enough, we
hypothesize causation. Science progresses by repeated testing
and attempted invalidation of causal hypotheses. Those that
survive the process persist.

The relationship between the seizure of a passenger in a
moving vehicle, which necessarily occurs when that vehicle is
stopped by the police, and the subsequent discovery of evidence
during that stop, is one of ineluctable and undeniable
correlation. The day has not dawned when a police officer can
effectuate a traffic stop without seizing all the occupants of the

39
vehicle.23 The correlation between that seizure and the
discovery of evidence during the stop is a perfect 100 percent.
As an empirical matter, therefore, the facts on the ground meet
the definition of but-for causation: you never see the one
without seeing the other first.

So should we hypothesize – or, given our institutional
position, perhaps “impose” is the better term – a causal
relationship between the seizure and the discovery of the
evidence? As detailed above, the dominant view in the circuits
is that the causal nexus between the traffic stop and the
discovery of evidence is self-evidently sufficient to support
suppression.

We agree that the causal relationship seems close, and
clear. But we will not pretend that we have no role in imposing,
as a legal matter, that causal relationship onto the fact pattern
before us, or that such judgments can be made with iron-clad
logical or empirical precision. We do not ignore the fact that the
analytic separation of individual constitutional violations is a
plausible logical deduction from the proposition that Fourth

23
Of course, the day may dawn – perhaps it already has –
when police may search the interior of a moving car without
stopping it or in any way restricting the freedom of movement
of the occupants, for example by employing remote electronic
devices. In such a situation, where no seizure of the car’s
occupants is effected, Rakas would control and passengers
would lack the right to suppress evidence discovered.

40
Amendment rights are personal. We do, however, reject such
separation.

We think the better view is that a traffic stop is a single
act, which affects equally all occupants of a vehicle. To us, that
description of traffic stops comports with the commonsense
experience of everyone who has ever ridden in a car; we agree
with the First Circuit that the distinction between passenger and
driver “is a distinction of no consequence in this context.”
Kimball, 25 F.3d at 5. A police officer who pulls over a vehicle
does not, in the act of pulling over the vehicle, interact
separately with each occupant; rather, the officer undertakes one
action – turning on the siren and lights – which instantly affects
everyone in the targeted vehicle, signaling to them that their
freedom of movement has been restricted. It defies common
sense and common experience to transmute one action into
three, and we will not endorse a Fourth Amendment approach
that relies on such a transmutation. The government insists that
“Fourth Amendment rights are personal rights,” and we do not
contest the abstract validity of that proposition. But general
propositions do not decide concrete cases, and we reject the
practical implications the government seeks to derive from that
proposition. We reject “blind adherence to a phrase which at
most has superficial clarity and which conceals underneath that
thin veneer all of the problems of line drawing which must be
faced in any conscientious effort to apply the Fourth
Amendment.” Rakas v. Illinois, 439 U.S. 128, 147 (1978).

Furthermore, the relationship between a traffic stop and
the discovery of evidence during that stop is not like the
relationship between two balls on a billiard table. Law is not

41
physics. In even its most aspirationally scientific
manifestations, the law recognizes and embraces the infusion of
a multiplicity of values into judicial determinations of causal
relationships, see, e.g., Carl F. Cranor & David A. Eastman,
Scientific Ignorance and Reliable Patterns of Evidence in Toxic
Tort Causation, 64 L. & Contemp. Prob. 5 (2001) (assessing the
extent to which courts are willing or able to assimilate and
evaluate scientific models of causation in complex cases), and
the Supreme Court has done so even more emphatically, and
recently, in the context of the exclusionary rule. Fourth
Amendment rules cannot be derived from deductive reasoning
from first principles, nor do they crystallize, unaided, from the
naked facts of disputed searches.

The Supreme Court has just this Term reiterated that the
exclusionary rule was founded on, and is grounded in, the
continuing exercise of pragmatic judicial supervision of the law
enforcement activities of the executive branch, effectuated by
expansion and contraction of the bubble of proximate cause as
courts face particular concrete factual situations. See Hudson v.
Michigan, 547 U.S. --- (2006) (eliminating suppression remedy
for knock-and-announce violations because, inter alia, as
compared with the 1950s, police departments are more likely to
be “staffed with professionals,” and lawyers are more likely to
take on § 1983 cases). The test by which our models of
constitutional causation are measured is not empirical validation
by experiment, but rather the march of social progress, refracted
through continual judicial evaluation of constitutional purposes
and social consequences. As the social context of law
enforcement evolves, so too does the exclusionary rule. The
debate about the constitutional consequences of traffic stops is

42
akin, in this respect, to the debate about the constitutional
consequences of electronic surveillance or computer copying.
See, e.g., Orin S. Kerr, Searches and Seizures in a Digital
World, 119 Harv. L. Rev. 531, 561 (2005) (pondering whether
electronic copying of computer files constitutes a “seizure,” and
if so what the appropriate Fourth Amendment remedy should
be).

The Supreme Court stressed in Hudson that in
determining whether a particular Fourth Amendment violation
is causally related to a particular challenged piece of evidence
in such a way as to trigger the exclusionary rule, we must look
not only to the logical relationship between the violation and the
discovery of the evidence, but also to the nature of the personal
and social interests the Constitution protects, the prevalence of
the illegal police practice at issue, the deterrent value of the
suppression remedy, and the likely practical effects of a
particular rule. See Hudson, slip op. at 8-13 (determining
constitutional suppression requirements based on evolving
social realities).

Applying these tests, we find that the purposes of the
Fourth Amendment are best served by extending the bubble of
proximate causation to vehicle passengers. Passengers, no less
than drivers, have a constitutional interest in protection from
unreasonable seizures. Two of the more constitutionally
troubling varieties of unreasonable seizures, both implicated in
this case, are those that occur when police stop vehicles based
on anonymous tips, or based on the race of the vehicle’s
occupants. While the Supreme Court may be right about the
increased professionalism of police and the robustness of the

43
§ 1983 plaintiffs’ bar, we cannot say that either racial profiling
or reliance on anonymous tips has declined in frequency in
recent years, or that civil lawsuits will adequately deter such
practices. Nor can we say that the various other categories of
cases that give rise to passenger suppression motions are rare,
decreasing, sufficiently internally disciplined, or otherwise
deterred. Furthermore, Americans spend more time in cars with
each passing year, see, e.g., Dep’t of Transportation, 2001
N ational H ousehold Travel Survey, available at
http://www.fhwa.dot.gov/policy/ohpi/nhts (reporting “dramatic
increases” in time spent driving between 1969 and 2000), and as
the circuit cases described above demonstrate, the use of traffic
stops as investigatory tools is a widespread and standard police
practice.24

24
That this practice is legitimate is at present beyond
constitutional cavil under Whren. However, the excesses its use
periodically engenders have not gone unnoticed, and in recent
years many police departments have studied and adopted
procedural reforms that may be implemented to monitor vehicle
stops and reduce the incidence of racial profiling and other
abuses of the seizure power on the roads. See, e.g., Robin
Shepard Engel, et al., Project on Police-Citizen Contacts (2004)
(report and recommendations prepared for Pennsylvania State
Police Commissioner Colonel Jeffrey Miller); New Jersey
Senate Judiciary Committee, The New Jersey Senate Judiciary
Committee’s Investigation of Racial Profiling and the New
Jersey State Police: Overview and Recommendations (2001)
(recommendations for reforms in wake of widely-publicized
racial profiling incidents). Such reforms can provide significant

44
 Furthermore, were we to allow the government to use
against Mosley the evidence recovered in this case, we would
weaken, indeed nearly eviscerate, the Supreme Court’s clear and
unanimous command in Florida v. J.L. that an anonymous tip is
a constitutionally deficient basis for an investigatory detention.
See 529 U.S. at 273-74. The Supreme Court did not, we
presume, contemplate that its plain constitutional holding could
be simply ignored as to all occupants of a vehicle other than the
driver, and we will not lightly countenance such a result.

Nor, finally, is the reductio ad absurdum presented above
(stationary mobile home versus moving mobile home) really all
that absurd. The level of justification required to support a valid
car search is extremely low, as we explained above, as compared
with that required to support a valid home search. Most
obviously, in contradistinction to house searches, there is no
general warrant requirement for car searches. See, e.g.,
Maryland v. Dyson, 527 U.S. 465, 467 (1999). Thus all
occupants of cars, drivers and passengers alike, are

protection for equal protection and due process rights, in
addition to Fourth Amendment rights, and we recognize that the
incentives created by the exclusionary rule have a significant
effect on police behavior. Allowing unfettered use against
passengers of evidence obtained during unconstitutional traffic
stops could undermine these reform efforts. And unlike the
knock-and-announce rule, the constitutional prohibitions on
racial profiling and reliance on anonymous tips do go the heart
of the validity of the underlying police action itself, not merely
the method of its execution.

45
overwhelmingly more likely to be subject to police scrutiny
when on the road than when at home. Of course, illegal police
entries into and searches of homes do occur. But the frequency
with which police effect forcible entries into homes is
incomparably less than the frequency with which they pull over
cars, and the teaching of Hudson is that such social facts matter.
If warrantless house searches were as common as roadside
traffic-stop searches, for example, then perhaps the protection
afforded houseguests in Minnesota v. Olson, 495 U.S. 91
(1990), might have been broader. The exclusionary rule
expresses, inherently and always, a standard of reasonableness
that evolves along with police practices and social norms.

The exclusionary rule is a judge-made remedy designed
to deter illegal police conduct. The Hudson decision has made
it clear, if there was ever any doubt, that decisions about both
the application of the rule are pragmatic decisions requiring
practical wisdom rather than syllogisms. Justice Scalia’s
opinion epitomizes such pragmatic balancing, “interpreting the
Constitution in light of its own practical concern for an active
liberty that is itself a practical process,” Stephen Breyer, Active
Liberty 74 (2005). It is in that spirit that we decide this case.

IV.

The car in which Mosley was riding was pulled over
illegally. Mosley was illegally seized the moment the car was
pulled over. The stopping of the vehicle was a but-for cause of
the discovery of the guns. The bubble of causation which links
a traffic stop to a subsequent search extends to all occupants of
the stopped vehicle. To overcome Mosley’s suppression

46
motion, therefore, the government would have had to establish
one of the traditional exceptions to the Wong Sun rule:
attenuation, inevitable discovery, independent source, or some
intervening act or event sufficient to purge the taint of the illegal
stop. The government raised no such exception at trial, and
raises none on appeal. We therefore hold that the guns were
fruit of the poisonous tree and must be suppressed.

Accordingly, we will vacate Mosley’s conviction, and
remand the case to the District Court for further proceedings
consistent with this opinion.

47