United States Court of Appeals

For the First Circuit

No. 11-1134

UNITED STATES OF AMERICA,

Appellee,

v.

CRAIG SPARKS,

Defendant, Appellant.

No. 11-1143

UNITED STATES OF AMERICA,

Appellee,

v.

BENJAMIN MICHAUD,

Defendant, Appellant.

APPEALS FROM THE UNITED STATES DISTRICT COURT

FOR THE DISTRICT OF MASSACHUSETTS

[Hon. William G. Young, U.S. District Judge]

Before

Howard, Circuit Judge,

Souter, Associate Justice, *

and Stahl, Circuit Judge.

Hon. David H. Souter, Associate Justice (Ret.) of the *

Supreme Court of the United States, sitting by designation.
Jeffrey W. Langholtz for appellant Craig Sparks.

Roger A. Cox for appellant Benjamin Michaud.

Robert E. Richardson, Assistant United States Attorney, with

whom Carmen Ortiz, United States Attorney, was on brief, for

appellee.

March 26, 2013
STAHL, Circuit Judge. In December 2009, federal agents,

acting without a warrant, placed a global positioning system (GPS)

tracker on a car used by appellant Craig Sparks. The agents used

the tracker to locate the car at the scene of a bank robbery and

then to chase down the car on the highway after it fled. A search

of the car revealed evidence tying Sparks and his fellow appellant

Benjamin Michaud to the bank robbery, leading to their indictment. 

Sparks and Michaud now appeal the district court's denial of their

motion to suppress that evidence, arguing that, under the Supreme

Court's recent decision in United States v. Jones, 132 S. Ct. 945

(2012), the agents' use of the GPS tracker was a Fourth Amendment

"search" that required a warrant. We affirm without reaching that

question, because we conclude that the agents' conduct fits within

the good-faith exception to the exclusionary rule.

I. Facts & Background

The facts of this case are not disputed. The Federal

Bureau of Investigation (FBI) suspected Sparks of committing three

bank robberies in late 2009. Accordingly, in the early hours of

December 24, 2009, FBI agents affixed a GPS tracker to a black

Chrysler sedan registered to Sparks's mother but used by Sparks

himself. At the time, the Chrysler was parked in a private parking

lot used by tenants of two adjacent residential buildings,

including Sparks himself. The agents did not have a warrant to

place the tracker on the car.

-2-
The GPS tracker enabled the agents to track the car's

location in real time by logging onto a website. The tracker had

its own battery and thus drew no power from the car. In fact, the

tracker's battery failed shortly after installation, prompting the

agents to replace the battery and reattach the tracker on December

29.

On January 4, 2010 (eleven days after the tracker's

initial installation), the agents, using the tracker, located the

Chrysler in Waltham, Massachusetts. When the agents reached the

car at approximately 12:15 p.m., it was parked near the

intersection of Ash and Crescent Streets, unoccupied but with the

engine running. The agents took up position nearby to watch the

car.

Roughly ten minutes later and two blocks away, two men

entered the Bank of America branch on Moody Street, wearing dark

clothing and ski masks and brandishing what appeared to be

handguns. They demanded money. After obtaining approximately

$10,676 in cash, they left the bank, and fled in a red SUV with the

license plate number 4205YN.

Moments later, the same red SUV pulled up across from the

Chrysler and two men in dark hooded sweatshirts, one of whom

carried a dark-colored bag, emerged. They ran to the Chrysler,

climbed in, and drove off. The watching agents tried to follow,

but became ensnarled in traffic. Thanks to the GPS tracker,

-3-
however, they located the Chrysler heading north on Route 128 and

caught up to it. As the car passed through Lexington, a

Massachusetts State Police cruiser attempted to pull it over, but

the Chrysler's driver slammed on the brakes, sending the car into

a ditch along the side of the highway. The two occupants fled into

the woods, temporarily evading the agents' grasp.

A quick search of the car revealed two BB guns that

resembled the weapons brandished by the bank robbers. A

subsequent, more thorough search uncovered further incriminating

evidence, including clothing and latex gloves like those worn by

the robbers, a knife and a dagger, identification belonging to both

defendants, and a screwdriver. (The latter was relevant because

the red SUV's ignition had been "popped," allowing it to be started

with a screwdriver. The SUV turned out to have been stolen in

Charlestown.) Investigators also found, in the woods into which

the suspects fled, $1,381 in cash and a bag containing two dark

hooded sweatshirts.

The Lexington Police apprehended defendant Michaud later

that afternoon. He was found with roughly $9,284 in cash (bearing

money bands from the bank), two black ski masks, and white latex

gloves. He was also wearing mismatched shoes, the mates of which

were found in the Chrysler. Sparks proved somewhat harder to

catch; he was ultimately collared in Maine a few weeks later.

-4-
After both defendants were indicted, Sparks moved to

suppress the evidence obtained as a result of the placement of the

GPS tracker on the Chrysler. United States v. Sparks, 750 F. Supp.

2d 384, 387 (D. Mass. 2010). Michaud entered a conditional guilty

plea and, with the district court's permission, joined Sparks's

suppression motion. See id. at 387 n.4. After thoroughly

considering the defendants' privacy interests in the parking lot

where the GPS tracker was installed, id. at 388-90, the exterior of

the car, id. at 390-91, and the information the tracker revealed

about their travel, id. at 391-96, the district court denied the

motion to suppress. The court concluded that the case was governed

by United States v. Knotts, 460 U.S. 276 (1983), which held that

using a radio-based tracking device to tail a suspect's car was not

a Fourth Amendment search, because "[a] person traveling in an

automobile on public thoroughfares has no reasonable expectation of

privacy in his movements from one place to another." Id. at 281. 

Sparks thus entered a guilty plea of his own, and the government

agreed that both defendants could appeal the suppression issue

(with a caveat as to Michaud that is not relevant here). The

district court sentenced each defendant to 188 months' imprisonment

and five years' supervised release.

II. Analysis

After the district court denied the motion to suppress,

the Supreme Court decided United States v. Jones, which held that

-5-
"the Government's installation of a GPS device on a target's

vehicle, and its use of that device to monitor the vehicle's

movements, constitutes a 'search'" for Fourth Amendment purposes. 

132 S. Ct. at 949 (footnote omitted). The Justices all agreed that

a search had occurred, but differed as to why. The five-Justice

majority held that a search occurred because "[t]he Government

physically occupied private property for the purpose of obtaining

information." Id. The majority opinion emphasized that the

government had committed a common-law trespass by installing the

tracker on the defendant's car. See id. at 949-50. Justice

Sotomayor provided the fifth vote for that position because she

agreed that a search occurs "at a minimum" where the government

obtains information via physical intrusion, id. at 954 (Sotomayor,

J., concurring), but wrote separately to caution that "physical

intrusion is now unnecessary to many forms of surveillance," and to

suggest that "some unique attributes of GPS surveillance . . . will

require particular attention" in future cases, id. at 955. 

Finally, Justice Alito, joined by Justices Ginsburg, Breyer, and

Kagan, took issue with the majority's trespass-based approach but

nevertheless found that a search had occurred under the reasonableexpectation-of-privacy test articulated in Katz v. United States,

389 U.S. 347 (1967). See 132 S. Ct. at 957-64 (Alito, J.,

concurring in the judgment).

-6-
Jones thus establishes that the district court's reason

for denying the suppression motion in this case -- that "the

placement of the GPS device on the vehicle cannot be considered a

search," 750 F. Supp. 2d at 391 -- is no longer sound. 

Consequently, this appeal turns on two questions that remain open

after Jones: whether the kind of search recognized in Jones and

conducted here requires a warrant (instead of mere probable cause

or reasonable suspicion), and, if so, whether the resulting

evidence can nevertheless avoid suppression under the good-faith

exception to the exclusionary rule articulated in Davis v. United

States, 131 S. Ct. 2419 (2011).1

Few courts (and no circuits that we know of) have

grappled with the warrant question so far, largely because the

searches at issue in recent cases occurred pre-Jones, allowing the

government to argue, and a number of courts to find, that the goodThe government does not dispute that Sparks, who did not 1

own the Chrysler but was its usual driver, has standing to

challenge the search here. See Jones, 132 S. Ct. at 949 n.2; cf.

United States v. Gibson, -- F.3d ---, 2013 WL 538007, at *18-19

(11th Cir. Feb. 14, 2013). Michaud, on the other hand, seems to

have had no equivalent interest in the Chrysler. See Sparks, 750

F. Supp. 2d at 387 n.4. Regardless, his suppression claim would

fail for the reasons given below, so we need not consider whether

he could show some other basis to challenge the search. See Orin

S. Kerr, Does Fourth Amendment Standing Work Differently for Jones

Trespass Searches, Traditional Katz Searches, and Long-term Katz

Searches?, The Volokh Conspiracy (Feb. 14, 2012, 10:30 p.m.),

http://www.volokh.com/2012/02/14/does-fourth-amendment-standingwork-differently-for-jones-trespass-searches-traditional-katzsearches-and-katz-long-term-expectation-of-privacy-searches/.

-7-
faith exception would apply even if the searches were

unconstitutional. E.g., United States v. Andres, 703 F.3d 828,

834-35 (5th Cir. 2013); United States v. Pineda-Moreno, 688 F.3d

1087, 1090 (9th Cir. 2012); see generally Caleb Mason, New Police

Surveillance Technologies and the Good-Faith Exception: Warrantless

GPS Tracker Evidence After United States v. Jones, 13 Nev. L.J. 60

(2012). Those courts that have found GPS tracking to require a

warrant have typically reached that conclusion by rejecting the

government's attempts to fit GPS tracking within the Fourth

Amendment's automobile exception. See United States v. Ortiz, 878

F. Supp. 2d 515, 535-36 (E.D. Pa. 2012); United States v. Katzin,

No. 11-226, 2012 WL 1646894, at *6 (E.D. Pa. May 9, 2012), appeal

pending, No. 12-2548 (3d Cir. argued Mar. 19, 2013). Some have

also more broadly considered the balance of privacy and

governmental interests at stake, concluding that the scales tip in

favor of requiring a warrant. United States v. Ford, No. 11-CR-42,

2012 WL 5366049, at *8 (E.D. Tenn. Oct. 30, 2012); Ortiz, 878 F.

Supp. 2d at 530-33; see also Jones, 132 S. Ct. at 955 (Sotomayor,

J., concurring) (emphasizing the impact that GPS monitoring can

have on a person's privacy); United States v. Maynard, 615 F.3d

544, 562 (D.C. Cir. 2010) (same), aff'd sub nom. Jones, 132 S. Ct.

945. But see United States v. Robinson, No. 11-CR-00361-AGF, 2012

WL 4893643, at *16-17 (E.D. Mo. Oct. 15, 2012) (relying on preJones precedent to find that reasonable suspicion sufficed).

-8-
Here, we need not decide whether the government can show

that GPS tracking is exempt from "the basic rule" that warrantless

searches are per se unreasonable, Arizona v. Gant, 556 U.S. 332,

338 (2009), because we agree with the government's alternative

argument: even if the agents' use of the GPS tracker in this case

was unconstitutional, their conduct fits within the good-faith

exception to the exclusionary rule. Under that exception, as

recently explicated in Davis, "searches conducted in objectively

reasonable reliance on binding appellate precedent are not subject

to the exclusionary rule." 131 S. Ct. at 2423-24. In this case,

suppression would be inappropriate because the agents' attachment

and monitoring of the GPS tracker was authorized by settled,

binding circuit precedent.

A. The scope of Davis's good faith exception

The purpose of the exclusionary rule "is to deter future

Fourth Amendment violations." Id. at 2426; see United States v.

Leon, 468 U.S. 897, 916 (1984). But the rule's deterrent value

must be balanced against the cost it imposes in the form of

probative but discarded evidence. See Davis, 131 S. Ct. at 2427. 

When the police comply with authoritative precedent, only to see

the law evolve after the fact, there is nothing to deter; the

police cannot modify their conduct to accord with cases not yet

decided. See id. at 2428-29, 2434. Thus, in Davis, where the

police conducted a vehicle search incident to arrest that strictly

-9-
complied with binding circuit precedent applying the bright-line

rule of New York v. Belton, 453 U.S. 454 (1981), suppression of the

resulting evidence was not appropriate even though Arizona v. Gant

subsequently established that the vehicle search was unlawful. 131

S. Ct. at 2428. Under the same principle, if the warrantless

installation and monitoring of the GPS tracker in this case was

"objectively reasonable" under then-"binding appellate precedent,"

suppression is not warranted, even if it turns out that the agents

should have gotten a warrant first. Id. at 2423-24.

The parties offer competing visions of what "objectively

reasonable reliance on binding appellate precedent" means. Sparks

and Michaud posit that, to qualify, the precedent in question must

be binding in this circuit (i.e., issued by the Supreme Court or

this court) and sufficiently apposite that "reasonable minds" could

not dispute the propriety of the police practice in question. A

number of district courts in other circuits have adopted similar

readings of Davis in the GPS context. E.g., Robinson, 2012 WL

4893643, at *14; Katzin, 2012 WL 1646894, at *9. On the other

hand, the government suggests that, in the absence of directly

applicable circuit precedent, law enforcement officers may

reasonably rely on the decisions of appellate courts outside the

circuit. This view, too, has found favor with some district courts

in GPS cases, including in this circuit. E.g., United States v.

Gordon, No. 11-CR-20752, 2013 WL 791622, at *8 (E.D. Mich. Mar. 4,

-10-
2013); United States v. Rose, No. 11-10062-NMG, 2012 WL 4215868, at

*4-5 (D. Mass. Sept. 14, 2012); United States v. Oladosu, 887

F. Supp. 2d 437, 442-48 (D.R.I. 2012).

The scope of Davis's reasonable-reliance-on-precedent

test turns on two subsidiary questions: what universe of cases can

the police rely on? And how clearly must those cases govern the

current case for that reliance to be objectively reasonable? As to

the first question, Davis itself establishes that the police

certainly may rely on binding circuit precedent. 131 S. Ct. at

2434. The Court's emphasis on the absence of police culpability

could be read to imply that good-faith reliance on out-of-circuit

appellate precedent is also acceptable. E.g., Rose, 2012 WL

4215868, at *5. That said, the Court did predict that "defendants

in jurisdictions in which [a given Fourth Amendment] question

remains open will still have an undiminished incentive to litigate

the issue," 131 S. Ct. at 2433, suggesting the opposite. In any 2

event, we need not consider today whether Davis can be extended to

reach reliance on non-binding authority, because we conclude that

We note that the federal and state appellate courts that 2

had already adopted a Davis-type reliance-on-precedent exception

before Davis was decided uniformly restricted that exception to

reliance on binding precedent. E.g., United States v. Davis, 598

F.3d 1259, 1266-67 (11th Cir. 2010), aff'd, 131 S. Ct. 2419. 

Likewise, the two appellate courts to consider the question since

Davis have read Davis to require reliance on "the caselaw of the

jurisdiction." Briscoe v. Maryland, 30 A.3d 870, 883 (Md. 2011);

accord United States v. Debruhl, 38 A.3d 293, 298 (D.C. 2012); see

also Mason, supra, at 82.

-11-
binding circuit precedent authorized the FBI agents' conduct in

this case. But before we explain that conclusion, we think it

helpful to briefly touch on the second question: how apposite must

the relied-on precedent be?

The Davis Court emphasized, and Davis himself did not

dispute, that the officers in that case "strict[ly]" and

"scrupulously" complied with circuit precedent. 131 S. Ct. at

2428, 2434. Thus, the Court was not faced with a situation where

the police conduct was "consistent with the language of a Fourth

Amendment rule . . . announced in a case with clearly

distinguishable facts," or where "the relevant precedent did not

directly announce any general rule but involved highly analogous

facts." Id. at 2437 (Breyer, J., dissenting). Nor does it appear

that any other circuit has yet considered the boundaries of

permissible reliance after Davis.

Before Davis was decided, however, a number of state and

federal courts (including the Eleventh Circuit, as affirmed in

Davis itself) had already adopted a Davis-type reliance-onprecedent exception to the exclusionary rule. They unanimously

held -- and we agree -- that the exception is available only where

the police rely on precedent that is "clear and well-settled." 

United States v. Davis, 598 F.3d 1259, 1266 (11th Cir. 2010),

aff'd, 131 S. Ct. 2419; see also United States v. McCane, 573 F.3d

1037, 1042 (10th Cir. 2009) (search was "wholly consistent with and

-12-
supported by" precedent); State v. Baker, 229 P.3d 650, 663 (Utah

2010) (precedent was "settled"); State v. Dearborn, 786 N.W.2d 97,

107 (Wis. 2010) (officers relied on "clear and settled law"). 

Indeed, the circuits that recognized the exception pre-Davis

stressed that their "precedent on a given point must be

unequivocal" for suppression to be withheld. Davis, 598 F.3d at

1266; accord United States v. Curtis, 635 F.3d 704, 714 n.28 (5th

Cir. 2011); United States v. Buford, 632 F.3d 264, 276 & n.9 (6th

Cir. 2011). We do not think Davis undermined their position. See

Mason, supra, at 64, 69 (arguing that Davis approved of the

Eleventh Circuit's approach below and therefore "the officer's

conduct must have been expressly authorized by clearly established

law" for Davis to apply). Rather, this emphasis on the clear

application of the precedent to the case at hand is consistent with

Davis's focus on deterrence; where judicial precedent does not

clearly authorize a particular practice, suppression has deterrent

value because it creates an "incentive to err on the side of

constitutional behavior." Davis, 598 F.3d at 1266-67 (quoting

United States v. Johnson, 457 U.S. 537, 561 (1982)) (internal

quotation marks omitted); see Davis, 131 S. Ct. at 2435 (Sotomayor,

J., concurring in the judgment); Wayne A. Logan, Police Mistakes of

Law, 61 Emory L.J. 69, 86-87 (2011); Mason, supra, at 71-72.3

The requirement that the precedent be clear and well- 3

settled is also consistent with the other circumstances in which

the Court has applied the good-faith exception. In particular,

-13-
B. Davis's good faith exception applies here

The foregoing principles require us to find that

suppression would be improper here. This is certainly a closer

question in this circuit than in those that had directly addressed

the propriety of warrantless GPS tracking prior to Jones. E.g.,

Pineda-Moreno, 688 F.3d at 1090. Nevertheless, we think the

Supreme Court's decision in Knotts, 460 U.S. 276, and ours in

United States v. Moore, 562 F.2d 106 (1st Cir. 1977), are

sufficiently clear and apposite to trigger Davis here.

In Moore, we considered the government's warrantless

installation and use of "beepers" (battery-powered radio

transmitters) to track the movements of the defendants' vehicles on

public roads. 562 F.2d at 110-13. We concluded that "[w]hile a

driver has no claim to be free from observation while driving in

public, he properly can expect not to be carrying around an

uninvited device that continuously signals his presence." Id. at

112. Balancing these considerations and the needs of law

enforcement, we held that "while the lessened expectancy of privacy

associated with motor vehicles justifies the use of beepers without

a warrant to track vehicles, this can be done only if the officers

have probable cause at the time." Id. at 112-13. Importantly for

reliance on a clear and well-defined judicial rule that is later

abrogated is analogous to reliance on a subsequently invalidated

statute, Davis, 598 F.3d at 1267, a circumstance that triggers the

good-faith exception under Illinois v. Krull, 480 U.S. 340 (1987).

-14-
present purposes, we focused almost exclusively on the defendants'

privacy interests in their movements, dismissing "the trespass

involved in affixing the beepers to the underbody of the vehicles"

as "so minimal as to be of little consequence." Id. at 111.

As the Moore court predicted, id. at 110, the issue of

beeper surveillance eventually reached the Supreme Court. In

Knotts, the Court held that "[a] person traveling in an automobile

on public thoroughfares has no reasonable expectation of privacy in

his movements from one place to another." 460 U.S. at 281. For

that reason, the use of a beeper to track the defendant's movements

on public roads involved "neither a 'search' nor a 'seizure' within

the contemplation of the Fourth Amendment." Id. at 285. Knotts

thus abrogated Moore's probable-cause requirement for beeper

surveillance, but it did not address the issue of a beeper's

installation on the defendant's property, see id. at 286 (Brennan,

J., concurring in the judgment), leaving undisturbed Moore's

conclusion that the trespass involved in attaching a beeper to a

car was "of little consequence."4

After Knotts and Moore, then, two points were settled in

this circuit. First, using a beeper to monitor a person's

Likewise, United States v. Karo, 468 U.S. 705 (1984), 4

held that no search or seizure occurred where the government

installed a beeper in an article that was later transferred to the

defendant (although subsequently monitoring the beeper inside a

private home was a search); like Knotts, Karo did not consider a

scenario in which the government installs a tracking device on

property that already belongs to the defendant. See id. at 712.

-15-
movements in a car on public roads did not implicate the Fourth

Amendment, because there was no privacy interest to be infringed. 

Id. at 281, 285 (majority opinion). Second, the trespass involved

in attaching a beeper to a car was, by itself, so insignificant as

to be essentially irrelevant for Fourth Amendment purposes. Moore,

562 F.2d at 111-12; see also United States v. Karo, 468 U.S. 705,

712-13 (1984) (noting that "a physical trespass is only marginally

relevant to the question of whether the Fourth Amendment has been

violated"). The question is thus whether the FBI's reliance on

these clear and settled principles to install a GPS tracker instead

of a beeper, and then to monitor it for over a week, was

objectively reasonable. We think it was.5

First, we conclude that Moore's dismissal of the initial,

trespassory installation of the beeper as essentially immaterial

would not apply any differently to the installation of a GPS

tracker. Indeed, the defendants have offered us no reason to

conclude that the act of affixing a GPS tracker to the

undercarriage of a car is, by itself, any different from installing

a beeper in the same fashion. Thus, Moore squarely supported the

agents' attachment of the GPS tracker to the Chrysler when it

A skeptic might wonder whether the agents in this case 5

actually had Moore and Knotts in mind when they attached the GPS

tracker to the Chrysler in December 2009, but we do not believe

(and the defendants do not argue) that Davis requires the

government to show actual, as well as objectively reasonable,

reliance. See Krull, 480 U.S. at 355.

-16-
happened (although Jones has since abrogated Moore's conclusion on

the trespass question, see 132 S. Ct. at 949).

The closer question is whether Knotts clearly and

expressly authorized the subsequent monitoring of the GPS tracker

for eleven days. Like the officers in Knotts, the FBI agents in

this case used an electronic tracking device to follow the

movements of a car. But they did two things differently: they used

a GPS unit instead of a beeper, and they tracked the car for eleven

days instead of a number of hours. Do either of these differences

place the agents' conduct beyond the scope of what Knotts clearly

permitted?

On this record, we think the fact that the device was a

GPS tracker rather than a beeper does not render Knotts

inapplicable. Certainly, a GPS tracker is more capable than a

beeper, "but nothing inheres in the technology to take it out of 6

Knotts's holding." United States v. Cuevas-Perez, 640 F.3d 272,

278 (7th Cir. 2011) (Flaum, J., concurring), cert. granted and

judgment vacated, 132 S. Ct. 1534 (2012). And the defendants have

not identified anything about this particular GPS device -- except

Compare Renée McDonald Hutchins, Tied Up in Knotts? GPS 6

Technology and the Fourth Amendment, 55 UCLA L. Rev. 409, 414-21

(2007) (describing the development and capabilities of GPS

technology), with Clifford S. Fishman, Electronic Tracking Devices

and the Fourth Amendment: Knotts, Karo, and the Questions Still

Unanswered, 34 Cath. U. L. Rev. 277, 281-82 (1985) (describing

beeper technology circa 1985); see also People v. Weaver, 909

N.E.2d 1195, 1199 (N.Y. 2009) (distinguishing GPS technology from

the beeper in Knotts).

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for the duration of its use, discussed below -- that could

meaningfully distinguish it from the beeper in Knotts. See United

States v. Hernandez, 647 F.3d 216, 221 (5th Cir. 2011) (upholding

the warrantless use of a GPS tracker that functioned essentially

like the beeper in Knotts); see also Knotts, 460 U.S. at 282, 284

(emphasizing that technological enhancement and increased police

efficiency do not make otherwise-lawful surveillance suspect under

the Fourth Amendment). Thus, Knotts clearly authorized the agents

to use a GPS-based tracking device in the place of a beeper. See

Andres, 703 F.3d at 835 (finding "any possible technological

differences between a 1981 'beeper' and the GPS device used in this

case" insufficient to make the government's pre-Jones reliance on

a Fifth Circuit beeper precedent unreasonable for good-faith

purposes).

That brings us to the duration of the monitoring: eleven

days here, versus less than a day in Knotts -- not a trivial

difference. But Knotts gave scant reason to think that the

duration of the tracking in that case was material to the Court's

reasoning. Rather, the Court appeared to apply a blanket rule that

"[a] person traveling in an automobile on public thoroughfares has

no reasonable expectation of privacy in his movements from one

place to another"; no such expectation attaches to information that

is, like one's public movements, "voluntarily conveyed to anyone

who wanted to look." 460 U.S. at 281. Knotts did note that

-18-
abusive "dragnet type" surveillance might be governed by "different

constitutional principles," id. at 284, but there was no suggestion

in the Knotts opinion that this rather brusque dismissal of the

defendant's Orwellian warnings imposed a concrete temporal

limitation on the case's apparently unqualified holding. Indeed,

at the time of the search in this case, Knotts was widely and

reasonably understood to stand for the proposition that the Fourth

Amendment simply was not implicated by electronic surveillance of

public automotive movements, because the latter was merely a more

efficient "substitute . . . for an activity, namely following a car

on a public street, that is unequivocally not a search within the

meaning of the amendment." United States v. Garcia, 474 F.3d 994,

996-97 (7th Cir. 2007); see also Gordon, 2013 WL 791622, at *8

(concluding that "Jones represents an unexpected development that

has shifted law enforcement's understanding of" Knotts and Karo);

Mason, supra, at 65 (until Jones, "everyone thought" the "key fact"

in Knotts and Karo "was that the cars were being monitored while

they were on public roads, where anyone could see them").

Ultimately, then, Knotts and Moore authorized the agents'

conduct here. Knotts's apparent bright-line rule that the Fourth

Amendment is unconcerned with police surveillance of public

automotive movements is analogous to Belton's bright-line rule

authorizing officers to search the passenger compartment of an

arrestee's car. See Davis, 132 S. Ct. at 2424. Thanks to Jones

-19-
and Gant, respectively, both rules have turned out not to be as

categorical as they seemed, but that is not a reason to penalize

the police for applying them faithfully before those clarifications

occurred. Id. at 2428. As the Eleventh Circuit did in Davis with

regard to the pre-Gant Belton rule, we emphasize that the apparent

clarity of the pre-Jones Knotts rule is "critical to our decision." 

Davis, 598 F.3d at 1267. Also crucial is the fact that Moore

plugged the gap left by Knotts and Karo: until Jones, it was the

law of this circuit that the trespass involved in installing a

tracking device on a car was, by itself, immaterial for Fourth

Amendment purposes. Moore, 562 F.2d at 111-12.

In sum: at the time of the GPS surveillance in this case,

settled, binding precedent in the form of Knotts and Moore

authorized the agents' conduct. Davis thus precludes suppression

of the resulting evidence, even if the agents' actions violated the

Fourth Amendment (which we do not decide). Accordingly, we affirm

the district court's ruling, albeit on different grounds. See

United States v. Sanchez, 612 F.3d 1, 4 (1st Cir. 2010).

III. Conclusion

Davis's good-faith exception is not a license for law

enforcement to forge ahead with new investigative methods in the

face of uncertainty as to their constitutionality. "The

justifications for the good-faith exception do not extend to

situations in which police officers have interpreted ambiguous

-20-
precedent or relied on their own extrapolations from existing

caselaw." Davis, 598 F.3d at 1267. The good-faith exception is,

however, properly applied in cases like this one (or Davis itself),

where new developments in the law have upended the settled rules on

which the police relied. Accordingly, we affirm the district

court's denial of Sparks and Michaud's motion to suppress.

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