United States v. Eldred

17‐3367‐cr
United States v. Eldred

UNITED STATES COURT OF APPEALS
FOR THE SECOND CIRCUIT

August Term 2018

(Argued: October 24, 2018 Decided: August 5, 2019
Amended: August 9, 2019)

No. 17‐3367‐cr
––––––––––––––––––––––––––––––––––––

UNITED STATES OF AMERICA

Appellee,

‐v.‐

ROBERT CLAY ELDRED

Defendant‐Appellant.

––––––––––––––––––––––––––––––––––––

Before: LIVINGSTON, CHIN, Circuit Judges, and CROTTY, District Judge.

Defendant‐Appellant Robert Clay Eldred (“Eldred”) was indicted on June
23, 2016 for knowingly accessing child pornography. He moved to suppress
evidence collected with the use of a government search program, the Network
Investigative Technique (“NIT”), which aided in the identification of his computer
despite his use of anonymizing software, saying the warrant that authorized use
of the NIT was invalid. His motion was denied, and he pled guilty while


Judge Paul A. Crotty, of the United States District Court for the Southern
District of New York, sitting by designation.

1
reserving his right to appeal the district court’s decision to deny suppression. We
agree with the district court that, regardless whether the warrant violated Federal
Rule of Criminal Procedure 41(b) and the Federal Magistrates Act, 28 U.S.C. § 636,
and whether such violations are also violative of the Fourth Amendment, law
enforcement officers acted in good faith in applying for and carrying out the
warrant. Accordingly, the judgment of the district court is AFFIRMED.

FOR APPELLEE: BARBARA A. MASTERSON (Gregory L.
Waples, on the brief), Assistant United States
Attorneys, for Christina E. Nolan, United
States Attorney for the District of Vermont,
Burlington, Vermont.

FOR DEFENDANT‐APPELLANT: BARCLAY T. JOHNSON (David L. McColgin,
on the brief), Assistant Federal Public
Defenders, for Michael L. Desautels, Federal
Public Defender for the District of Vermont,
Burlington, Vermont.

DEBRA ANN LIVINGSTON, Circuit Judge:

This case arises from one of the many prosecutions following the

investigation by the Federal Bureau of Investigation (“FBI”) into Playpen, a child

pornography site located on the dark web. The FBI infiltrated the website and

discovered the identities of many registered users by deploying a search program,

the Network Investigative Technique (“NIT”), which allowed the FBI to

circumvent the anonymizing features of the dark web and collect computer‐

related identifying information, including internet protocol (“IP”) addresses, from

the computers of these Playpen users. Defendant‐Appellant Robert Clay Eldred

2
(“Eldred”), whose information was collected by the NIT, moved to suppress

evidence gathered by the program, arguing that the warrant authorizing it was

invalid. This motion was denied. Like the nine other circuits to have

considered the question thus far, we conclude that Eldred’s claim is without merit:

even assuming, arguendo, that the NIT warrant violated the Fourth Amendment,

law enforcement officers acted in good faith and suppression is not warranted.

We therefore AFFIRM the judgment of the district court.

BACKGROUND

I. Factual Background1

Playpen operated on the “The Onion Router” (better known as “Tor”), an

“anonymizing network” that allows users who have downloaded the Tor software

to access websites without revealing their IP addresses or other identifying

information by routing their internet traffic through numerous relay computers

located around the world before such traffic arrives at a desired web location.

These relay computers, which are owned by volunteers who donate their

bandwidth to Tor, are known as “nodes.” Because of this indirect routing, when

1 The factual background presented here is derived from the parties’ filings and
testimony and evidence before the district court at the suppression hearing, held on
January 19, 2017.

3
someone—for example, a law enforcement officer—attempts to view a Tor user’s

IP address in order to identify the user’s computer and ascertain its whereabouts,

the IP address displayed is actually that of the Tor “exit node,” i.e., the last

computer through which the user’s traffic was relayed, rather than the actual

address of the Tor user. Tor was originally developed and deployed by the U.S.

Naval Research Laboratory to protect government communications, but it is now

used by the public at large.

Certain websites on Tor, called “hidden services,” are available only to Tor

users on the Tor network. Instead of a typical web address, these hidden services

are assigned a randomly generated list of characters ending with the suffix

“.onion.” Law enforcement cannot determine the location of computers hosting

these hidden services using traditional IP lookup techniques. As these websites

are not indexed on the traditional Internet, they also don’t appear in searches run

using traditional search engines—a Tor user must know the web address in order

to access a hidden service. Playpen was one such website.

When a Tor user typed Playpen’s “.onion” address into Tor and arrived at

the site’s homepage for the first time, he was required to register with a username

and password in order to enter the site. By clicking on the “register an account”

4
hyperlink, new users accessed a Playpen message instructing them that: (1) while

“[t]he software we use for this forum requires that new users enter an email

address . . . the forum operators do NOT want you to enter a real address”; (2)

users should refrain from posting any information that could be used to identify

them; and (3) that “it is impossible for the staff or the owners of this forum to

confirm the true identity of users . . . .” Joint Appendix (“J.A.”) 47. After

successfully registering, users could access a variety of child pornography,

including images and videos indexed according to victim age, gender, and type of

sexual activity depicted, as well as content related to child pornography.

Although several of the site’s forums involved general information and rules

regarding the site, Playpen as a whole was “dedicated to the advertisement and

distribution of child pornography,” id. at 43, and included forums in which users

exchanged information about obtaining child pornography and engaging in child

sexual abuse. In addition to images and discussions, Playpen also contained a

private message feature. Available historical data suggests that Playpen had

over 1,500 unique users a day and over 150,000 registered users.

The FBI began investigating Playpen in September 2014. In January 2015,

FBI agents obtained a search warrant allowing the FBI to seize a copy of the server

5
hosting Playpen, which it installed on a server at a government facility in Virginia.

On February 19, 2015, the FBI executed a court‐authorized search on the Naples,

Florida home of the suspected administrator of the Playpen site. At that point

the FBI was able to assume administrative control of Playpen. However, because

of the anonymizing features of the Tor network, even with control of the website,

the FBI could not identify other administrators or site users.

For this reason, the FBI had developed the NIT, computer code which was

added to the digital content of the copy of the Playpen website residing on the

government server in Virginia. Once the NIT was deployed, whenever Tor users

accessed Playpen and downloaded content so as to display it on their computers,

that content was augmented with a set of computer instructions that traveled with

it, through Tor’s network of relay computers, until coming to rest on the computer

of the Playpen user. When the NIT reached the Playpen user’s computer, the

attached instructions executed, causing the user’s computer to transmit

identifying information back to the government server in Virginia, including, inter

alia, an IP address, the type of operating system employed by the computer and

an active operating system username, and information regarding whether the NIT

had previously been delivered.

6
 On February 20, 2015, in the Eastern District of Virginia, where the

government server then hosting Playpen was located, Magistrate Judge Theresa

Carroll Buchanan issued a warrant to deploy the NIT (the “NIT warrant”). An

attachment to the warrant listed the “[p]lace to be [s]earched” as “activating

computers,” i.e., “those of any user or administrator who logs into the [Playpen

website] by entering a username and password.” J.A. 32. The NIT would

collect from all “activating computers,” wherever located, their actual IP

addresses, as well as other specified pieces of information. While doing so, the

NIT would not deny the users any functionality on their computers, or collect any

additional, unrelated information. The listed information could then be used to

identify the Playpen user’s true identity and location. Acting under authority of

the NIT warrant, the FBI operated Playpen for about two weeks, from February 20

until March 4, 2015, from the server in the Eastern District of Virginia.

On March 4, 2015, a Playpen user identified only by the username

“robertecach” entered the site and thereafter spent over an hour accessing three

separate posts that contained images of prepubescent girls involved in genital

exposure, oral sex, and penetration by what appeared to be an adult male penis.

Through the use of the NIT, the FBI learned the IP address associated with

7
“robertecach,” as well as the fact that the computer name for the device that

accessed the site was “Robert.” Agents traced the IP address to an address in East

Montpelier, Vermont. Further investigation revealed that the house located at

that address comprised two residences, one in the basement. An FBI agent

thereafter interviewed the owners, who listed Eldred among previous tenants of

the basement unit and confirmed that he shared the house’s wireless connection

with them.

FBI agents visited Eldred’s subsequent residence in Northfield, Vermont on

March 15, 2016, but found Eldred away at work. His girlfriend, Holly Belanger,

and Eldred’s adult son were both present and spoke with the agents. Belanger

confirmed that she and Eldred had lived at the address in East Montpelier in

March 2015, and that Eldred still used the same laptop he had used at that time.

She said that he had previously used the username “robertecache1” and that his

laptop was password‐protected, while Eldred’s son said that Eldred had used the

email address “robertecache@hotmail.com,” and that Eldred would not allow

others to use his laptop. Agents called Eldred, who refused to consent to a search

of his laptop but agreed to meet with agents the following day. The agents then

seized the laptop. After meeting with Eldred, who admitted he had used

8
“robertecach” as a previous email account and had lived in the East Montpelier

basement apartment, the agents applied for and received a warrant from

Magistrate Judge John M. Conroy in the United States District of Vermont to

search the laptop. The search revealed 116 files relating to child pornography,

including images of penile‐vaginal intercourse, penetration with objects, and oral

sex.

II. Procedural History

Eldred was indicted on June 23, 2016 for knowingly possessing child

pornography in violation of 18 U.S.C. § 2252(a)(4)(B). In November 2016 he

moved to suppress all evidence and statements obtained as a result of the NIT

warrant, arguing that it was invalid as Magistrate Judge Buchanan in the Eastern

District of Virginia did not have jurisdiction to authorize searches outside of her

district. He also moved to suppress evidence collected as a result of the Vermont

warrant, arguing that it lacked probable cause.

On February 17, 2017 Judge Geoffrey W. Crawford of the United States

District Court for the District of Vermont denied Eldred’s motion to suppress in

its entirety. While he agreed with Eldred that the NIT warrant was issued in

violation of Federal Rule of Criminal Procedure 41(b) (“Rule 41(b)”), Judge

9
Crawford concluded this rule violation was not of constitutional dimension.

Citing this Court’s decision in United States v. Burke, 517 F.2d 377, 386‐87 (2d Cir.

1975), the district court determined that application of the exclusionary rule was

not warranted, given that no Fourth Amendment violation had occurred, Eldred

had suffered no prejudice, and the FBI agents had not acted with deliberate

disregard for Rule 41, but in good faith. Furthermore, the Vermont warrant was

supported by probable cause.

Eldred pled guilty, but reserved his right to challenge the district court’s

denial of his motion to suppress. He was sentenced to six months in prison and

a five‐year term of supervised release. He timely filed a motion to appeal.

DISCUSSION

On appeal from a district court’s ruling on a suppression motion, “we

review a district court’s findings of fact for clear error, and its resolution of

questions of law and mixed questions of law and fact de novo.” United States v.

Bohannon, 824 F.3d 242, 247‐48 (2d Cir. 2016). Furthermore, we review a district

court’s determination to apply the good‐faith exception based on an officer’s

reliance on an issued warrant de novo. United States v. Raymonda, 780 F.3d 105,

113 (2d Cir. 2015).

10
 On appeal, Eldred argues that the NIT warrant violated both Rule 41(b)2

and the Federal Magistrates Act, 28 U.S.C. § 636(a).3 He further contends that

because Magistrate Judge Buchanan lacked jurisdiction to issue the NIT warrant

to search computers outside the Eastern District of Virginia, suppression should

have been granted, and the good‐faith exception is either unavailable or

inapplicable in this case. We note that after the NIT warrant issued, Rule 41(b)

2 Rule 41(b) provides generally that a magistrate judge “has authority to issue a
warrant to search for and seize a person or property located within the [magistrate
judge’s] district,” but also authorizes the issuance of warrants pertaining to persons or
property located outside the district in specified circumstances. At the time the NIT
warrant was deployed, the Rule provided for issuance of the latter type of warrant for:
(1) “a person or property outside the district if the person or property is located within
the district when the warrant is issued but might move or be moved outside the district
before the warrant is executed”; (2) in investigations of domestic or international
terrorism; (3) for the installation within the district of a tracking device, to track
movement of a person or property both within and without the district; and (4) for
property located outside of any federal district. Fed. R. Crim. Pr. 41(b). None of these
provisions “expressly allow[ed] a magistrate judge in one jurisdiction to authorize the
search of a computer in a different jurisdiction.” United States v. Horton, 863 F.3d 1041,
1047 (8th Cir. 2017).
3 Section 636(a) provides in relevant part as follows:
Each United States magistrate judge serving under this
chapter shall have within the district in which sessions are
held by the court that appointed the magistrate judge, at other
places where that court may function, and elsewhere as
authorized by law – (1) all powers and duties conferred or
imposed upon United States commissioners by law or by the
Rules of Criminal Procedure for the United States District
Courts . . . .

11
was amended specifically to authorize warrants such as the NIT warrant here.4

However, as this subsection did not become effective until 2016, it cannot be said

to have authorized the warrant in this case. Nevertheless, we conclude that it is

unnecessary to address the majority of Eldred’s contentions as, agreeing with nine

of our sister circuits, we ultimately conclude that even if the NIT warrant violated

the Fourth Amendment, the good‐faith exception applies.5

I

Rapid technological change can affect both the opportunities for criminal

behavior and its detection. In recent years law enforcement officials with

expertise in investigating child sexual exploitation have remarked on an increase

4 The 2016 amendment added Rule 41(b)(6), which provides the following, in
relevant part:
[A] magistrate judge with authority in any district where
activities related to a crime may have occurred has authority
to issue a warrant to use remote access to search electronic
storage media and to seize or copy electronically stored
information located within or outside that district if . . . the
district where the media or information is located has been
concealed through technological means . . . .
5 See United States v. Ganzer, 922 F.3d 579, 587‐90 (5th Cir. 2019); United States v.
Moorehead, 912 F.3d 963, 967‐71 (6th Cir. 2019); United States v. Henderson, 906 F.3d 1109,
1117‐20 (9th Cir. 2018); United States v. Kienast, 907 F.3d 522, 526‐29 (7th Cir. 2018); United
States v. Werdene, 883 F.3d 204, 215‐18 (3d Cir. 2018); United States v. McLamb, 880 F.3d
685, 690‐91 (4th Cir. 2018); United States v. Levin, 874 F.3d 316, 321‐24 (1st Cir. 2017); United
States v. Horton, 863 F.3d at 1049‐52 (8th Cir. 2017); United States v. Workman, 863 F.3d
1313, 1317‐21 (10th Cir. 2017).

12
in the technological savvy of the perpetrators of such crimes, particularly in their

use of anonymization methods. See Susan Hennessey, The Elephant in the Room:

Addressing Child Exploitation and Going Dark, Hoover Institution, Aegis Paper Series

No. 1701, at 5‐6 (2017). The proliferation of anonymization networks such as Tor

has at the same time rendered “certain law enforcement techniques for electronic

search and seizures . . . no longer effective.” Jonathan Mayer, Government

Hacking, 127 YALE L.J. 570, 577 (2017). Investigators who in the past “used to be

able to subpoena an Internet Service Provider (ISP) for an online suspect’s

identity,” id., may today engage in more elaborate “watering hole” strategies of

the sort employed in this case—where law enforcement agents operate a hidden

service in order to deliver malware to identify suspects who “interact with the

website under certain triggering conditions—for example, by visiting, logging in,

or going to specific webpages,” id. at 584.

The debate between privacy and security in our era of rapidly changing

technology is not new. See Carpenter v. United States, 138 S. Ct. 2206, 2233 (2018)

(Kennedy, J., dissenting) (“Technological changes . . . have complex effects on

crime and law enforcement.”). Nor is it novel to remark that rapid technological

change poses the challenge of defending in new contexts the Fourth Amendment’s

13
fundamental “right of the people to be secure in their persons, houses, papers, and

effects, against unreasonable searches and seizures.” U.S. Const. amend IV.

Even outside the dark web, “[t]he shift to a global Internet” is recognized to have

“major implications” for Fourth Amendment law. Orin S. Kerr, The Fourth

Amendment and the Global Internet, 67 STAN. L. REV. 285, 288 (2015). In particular,

the globalization of Internet traffic has left many asking just “how Fourth

Amendment law should adapt to the reality of a global network in which suspects,

victims, and evidence might be located anywhere.” Id. at 289.

This case is illustrative of the Fourth Amendment issues that can arise in

Internet investigations involving dispersed actors in unknown physical locations.

Eldred argues that the NIT warrant in this investigation, purporting to authorize

“searches that were executed in judicial districts across the United States,” Def.‐

App. Br. at 2, in fact “exceeded the magistrate judge’s territorial jurisdiction and

violated Federal Rule of Criminal Procedure 41 and 28 U.S.C. § 636,” id. at 15.

Eldred further contends that because Magistrate Judge Buchanan lacked

jurisdiction to issue the NIT warrant, it was void ab initio, and thus not a warrant

at all, in Fourth Amendment terms. Three of our nine sister circuits to have

considered the NIT warrant have accepted at least aspects of this argument. See,

14
e.g., United States v. Henderson, 906 F.3d 1109, 1117 (9th Cir. 2018) (concluding that

“a warrant purportedly authorizing a search beyond the jurisdiction of the issuing

magistrate judge is void under the Fourth Amendment”); United States v. Werdene,

883 F.3d 204, 214 (3d Cir. 2018) (“[T]he Rule 41(b) violation was of constitutional

magnitude because at the time of the framing . . . a warrant issued for a search or

seizure beyond the territorial jurisdiction of a magistrate’s powers under positive

law was treated as no warrant at all.” (internal quotation marks omitted)); Horton,

863 F.3d at 1049 (“We . . . find that the NIT warrant was void ab initio, rising to the

level of a constitutional infirmity.”).

For the reasons set forth below, we need not address Eldred’s claim that the

Fourth Amendment was violated by use of the NIT warrant. We note, however,

that the issue is not clear cut. Both Rule 41(b) and § 636(a) impose territorial

constraints on the authority of magistrate judges to issue particular types of

warrants, but the Fourth Amendment itself says nothing about where such

authority may be exercised, nor whether a venue requirement exists as a matter of

Fourth Amendment law. See Dalia v. United States, 441 U.S. 238, 255 (1979)

(noting that the Court has interpreted the Fourth Amendment “to require only

three things”: issuance by a “neutral, disinterested magistrate[,]” probable cause,

15
and particularity). Some have grounded such a requirement in the concept of a

“neutral and detached magistrate.” See United States v. Taylor, 250 F. Supp. 3d

1215, 1235 (N.D. Al. 2017) (“[I]nherent in the notion of a ‘neutral, detached

magistrate’ is that the magistrate have authority to issue the warrant.” (emphasis

omitted)); see also United States v. Krueger, 809 F.3d 1109, 1124 (10th Cir. 2015)

(Gorsuch, J., concurring) (“The principle animating the common law at the time of

the Fourth Amendment’s framing was clear: a warrant may travel only so far as

the power of its issuing official.”). But assuming, arguendo, that there is a

constitutional dimension to some cases in which a warrant might exceed territorial

limits set by statute or by rule, it is not clear that all such cases present viable

Fourth Amendment claims, particularly in a technological context in which both

crimes and the evidence to prove their commission are digitized, and detached

from the offline locations of suspects, confederates, and victims.

Here, for instance, even assuming that Magistrate Judge Buchanan in fact

lacked jurisdiction to issue a NIT warrant to authorize the retrieval of information

from computers located outside the Eastern District of Virginia, there is no dispute

that she had authority as to computers within that district. At least one sister

circuit has determined, as a result, that the NIT warrant “was not void ab initio,

16
for the warrant could validly be executed by extracting data from computers

within the magistrate judge’s district (the Eastern District of Virginia).” United

States v. Workman, 863 F.3d 1313, 1318 n.1 (10th Cir. 2017) (emphasis added); but

see Horton, 863 F.3d at 1049 (rejecting argument that “[t]he possibility that the

magistrate could have executed a proper warrant in the Eastern District of Virginia

. . . save[s] this warrant from its jurisdictional error); Werdene, 883 F.3d at 214 n.9

(same).

Several of the nine sister circuits to have addressed the NIT warrant here

have noted that the situation that arose in this case will not recur due to the

passage of the 2016 amendments to Rule 41(b). See, e.g., Werdene, 883 F.3d at 218

(“[E]ven though Rule 41(b) did not authorize the magistrate judge to issue the NIT

warrant, future law enforcement officers may apply for and obtain such a warrant

pursuant to Rule 41(b)(6), which went into effect in December 2016 to authorize

NIT‐like warrants.”); see also Hennessey, Elephant in the Room, at 16 (“The

December 1 rule change effectively moots the issue for future investigations.”).

But even this point is not beyond doubt. In relevant part, the Federal Magistrates

Act provides that a magistrate judge has the powers and duties conferred or

imposed by the Rules of Criminal Procedure “within the district in which sessions

17
are held by the court that appointed the magistrate judge, at other places where

that court may function, and elsewhere as authorized by law.” 28 U.S.C. § 636(a).

Such language, in the view of some courts, “imposes independent territorial

restrictions on the powers of magistrate judges” specifically, so that even

assuming Rule 41(b) “grants to magistrate judges the power to do certain specified

things,” this is only if otherwise permissible pursuant to the Federal Magistrates

Act, “a question the rules themselves do not purport to answer and that can be

answered only by circling back to § 636(a).” Krueger, 809 F.3d at 1121 (Gorsuch,

J., concurring); see also Henderson, 906 F.3d at 1115 n.5 (referencing but declining to

consider NIT warrant’s validity pursuant to the “independent territorial

limitations imposed upon a magistrate judge’s jurisdiction by § 636 itself”). If the

scope of Judge Buchanan’s authority to issue the NIT warrant “[wasn’t] merely

one of rule, . . . [but] of statutory dimension,” Krueger, 809 F.3d at 1122 (Gorsuch,

J., concurring), the recent amendments to Rule 41 may not alone be sufficient to

answer the question whether a magistrate judge, as opposed to a district court

judge, has authority to issue NIT‐style warrants pursuant to the amended Rule.

See Mayer, Government Hacking, at 627‐28 (suggesting, as a result, that “[w]hen the

government intends to search a computer but does not know the computer’s

18
location,” a warrant application should be submitted to a district court judge).

Thus, the Fourth Amendment issues raised by Eldred could recur, but now

pursuant to § 636(a) alone.

But that issue is not before us today. Nor need we determine whether the

NIT warrant in this case in fact issued in violation of the pre‐amendment Rule 41(b)

or § 636(a) of the Federal Magistrates Act. For as we discuss below, regardless

whether Magistrate Judge Buchanan exceeded the scope of her jurisdiction

pursuant to either of these provisions, we agree with the nine previous circuits to

have considered the issue and conclude that suppression is not warranted because

the good‐faith doctrine applies.

II

The Fourth Amendment protects the “right of the people to be secure in

their persons, houses, papers, and effects, against unreasonable searches and

seizures.” U.S. Const. amend IV. To effectuate this right, courts have created

an exclusionary rule “that, when applicable, forbids the use of improperly

obtained evidence at trial.” Herring v. United States, 555 U.S. 135, 139 (2009).

Nevertheless, “the exclusionary rule is not an individual right and applies only

where it results in appreciable deterrence.” Id. at 141 (internal quotation marks

19
and brackets omitted). “[E]vidence obtained in objectively reasonable reliance

on a subsequently invalidated search warrant cannot justify the substantial costs

of exclusion” and will not be suppressed. United States v. Leon, 468 U.S. 897, 922

(1984); see also Davis v. United States, 564 U.S. 229, 238 (2011) (noting that exclusion

is not required when police act “with an objectively reasonable good‐faith belief

that their conduct is lawful” or when police conduct “involves only simple,

isolated negligence” (internal quotation marks omitted)).

The good‐faith exception first recognized in Leon holds that when the agents

executing a search warrant “act with an objectively reasonable good‐faith belief’

that their conduct is lawful,” improperly obtained evidence remains admissible

because in such circumstances, “the deterrence rationale loses much of its force,

and exclusion cannot pay its way.” Davis, 564 U.S. at 238 (internal quotation

marks omitted). Granted, the Supreme Court in Leon delineated several

situations in which the good‐faith exception does not apply :

(1) the magistrate or judge “was misled by information in an affidavit that

the affiant knew was false or would have known was false except for his

reckless disregard of the truth”;

(2) “where the issuing magistrate wholly abandoned his judicial role”;

20
 (3) a warrant was based on an affidavit “so lacking in indicia of probable

cause as to render official belief in its existence entirely unreasonable”; and

(4) a warrant is so “facially deficient” that officers “cannot reasonably

presume it to be valid.”

Leon, 468 U.S. at 923 (internal quotation marks omitted). These situations align

broadly with the recognition that “[t]he extent to which the exclusionary rule is

justified by . . . deterrence principles varies with the culpability of the law

enforcement conduct.” Herring, 555 U.S. at 143. But none of the circumstances

recognized in Leon are applicable here.

Eldred in fact makes no argument for any but the fourth. He contends that

the NIT warrant was “facially deficient” because it—as opposed to the affidavit

supporting the warrant’s application—was limited to the Eastern District of

Virginia and did not encompass Vermont or the many other judicial districts to

which the FBI’s computer instructions were delivered. Of course, “[t]he Fourth

Amendment by its terms requires particularity in the warrant, not in the

supporting documents.” Groh v. Ramirez, 540 U.S. 551, 557 (2004). But while we

do not “rely on unincorporated, unattached supporting documents to cure a

constitutionally defective warrant, those documents are still relevant to our

21
determination of whether the officers acted in good faith.” United States v. Rosa,

626 F.3d 56, 64 (2d Cir. 2010). Here, we agree with the Eighth Circuit that upon

reading the affidavit—which describes in great detail how the NIT was to work—

“a reasonable reader would have understood that the search would extend beyond

the boundaries of the district,” supporting the officers’ good faith reliance.

Horton, 863 F.3d at 1052.

Moreover, even if we exclude consideration of the affidavit as not

sufficiently incorporated into the search warrant, as Eldred urges for the first time

on appeal, the warrant itself does not contain clear geographic limitations on the

place to be searched. Quite the opposite—Attachment A to the NIT warrant

refers to the place to be searched as all “activating computers,” defined in relevant

part as “any user . . . who logs into” Playpen. J.A. 32 (emphasis added). We thus

agree with the Eighth Circuit again that there is no “obvious deficiency” in the

warrant, which a number of courts have found facially valid. Horton, 868 F.3d at

1052; see also Leon, 468 U.S. at 923 (observing that a “facially deficient” warrant

merits exclusion when “the executing officers cannot reasonably presume it to be

valid”).

22
 We also disagree with Eldred that actions taken by the government

surrounding this warrant more broadly demonstrate the sort of “deliberate,

reckless, or grossly negligent conduct” that the exclusionary rule exists to deter.

Herring, 555 U.S. at 144. To support this argument, Eldred points to the

Department of Justice’s letter to the Advisory Committee on Criminal Rules

urging an amendment to Rule 41(b), suggesting this letter demonstrates the

government’s awareness that a NIT warrant like the one issued here did not fall

within the scope of Rule 41 at that time. Furthermore, he suggests that because

several different offices within the Department—and employees at different levels

within those offices—reviewed the warrant before presenting it to Magistrate

Judge Buchanan, we must differentiate a case like this from the typical case in

which we decline to impute detailed knowledge of the law to police or other law

enforcement officers. We turn to a sister circuit, the Fourth Circuit, which has

previously addressed this very argument:

[I]n light of rapidly developing technology, there will not
always be definitive precedent upon which law
enforcement can rely when utilizing cutting edge
investigative techniques. In such cases, consultation
with government attorneys is precisely what Leon’s
“good faith” expects of law enforcement. We are
disinclined to conclude that a warrant is “facially
deficient” where the legality of an investigative

23
 technique is unclear and law enforcement seeks advice
from counsel before applying for the warrant.

United States v. McLamb, 880 F.3d 685, 691 (4th Cir. 2018); see also United States v.

Levin, 874 F.3d 316, 323 (1st Cir. 2017) (noting “no benefit in deterring” the

government from “turn[ing] to the courts for guidance” when faced with a novel

legal question such as whether an NIT warrant can issue). Moreover, like our

sister circuits, “we do not construe the government’s efforts to have Rule 41(b)

amended . . . as an admission that [NIT] warrants were not previously allowed,

but rather as an attempt to clarify an existing law’s application to new

circumstances.” United States v. Ganzer, 922 F.3d 579, 589 (5th Cir. 2019). The

affidavit attached to the application for the NIT warrant in this case was over thirty

pages long and explained the procedure of the NIT and the circumstances of the

Playpen investigation in meticulous detail. We do not see how such

comprehensive disclosure by the government can be deemed a “knowing

disregard” for the rules, Def.‐App. Br. at 56, even if a magistrate judge may have

subsequently misunderstood her authority to grant such an application.

Lastly, to the extent that Eldred argues the good faith exception

categorically cannot apply when a warrant is issued by a judge lacking jurisdiction

and is thus void ab initio, we do not agree. Again, we need not—and do not—

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pass on the issue whether the warrant here was void ab initio, and for this reason

violative of the Fourth Amendment. See Herring, 555 U.S. at 141 (separating

analysis of potential constitutional violation from application of exclusionary

rule). Eldred’s proposed categorical exclusion from the good faith exception is

easily disposed of, even assuming arguendo that the NIT warrant was

constitutionally infirm.

As the Supreme Court has repeatedly stated, the exclusionary rule cannot

be used to penalize law enforcement officers for a magistrate’s error. See Leon, 468

U.S. at 921 (“Penalizing the officer for the magistrate’s error, rather than his own,

cannot logically contribute to the deterrence of Fourth Amendment violations.”);

see also Davis, 564 U.S. at 246 (“[W]e have said time and again that the sole purpose

of the exclusionary rule is to deter misconduct by law enforcement.”);

Massachusetts v. Sheppard, 468 U.S. 981, 989‐90 (1984) (“[W]e refuse to rule that an

officer is required to disbelieve a judge who has just advised him, by word and by

action, that the warrant he possesses authorizes him to conduct the search he has

requested.”). In Leon, for instance, the Supreme Court upheld the use of evidence

collected in reliance on a search warrant that a magistrate judge had erroneously

issued despite the absence of probable cause. See 468 U.S. at 925‐26. The

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constitutional deficiencies of that warrant did not require exclusion of the evidence

thereby obtained because the officers’ reasonable reliance on the warrant did not

implicate the deterrent purposes of the exclusionary rule. Even assuming,

arguendo, that statutory or rule limitations on a magistrate judge’s jurisdiction also

rise to the level of independent constitutional requirements, we see no reason to

treat a magistrate judge’s non‐compliance with these requirements differently

than non‐compliance with a fundamental Fourth Amendment constraint on the

issuance of warrants, such as probable cause.

We therefore agree with our sister circuits that the good‐faith exception is

applicable even when a warrant is void ab initio, so long as the law enforcement

agents executing such a warrant had an objectively reasonable belief that it was

valid. See Horton, 863 F.3d at 1050; see also Henderson, 906 F.3d at 1118 (rejecting

inapplicability of good‐faith exception to warrant that is void ab initio because

“good faith exception does not depend on the existence of a warrant, but on the

executing officers’ objectively reasonable belief that there was a valid warrant”);

United States v. Kienast, 907 F.3d 522, 528 (7th Cir. 2018) (noting that “whether the

magistrate judge lacked authority has no impact” on availability of good‐faith

exception for police). The exception properly “applies to warrants that are void

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ab initio” in such circumstances because “‘the issuing magistrate’s lack of authority

has no impact on police misconduct.’” Werdene, 883 F.3d at 216 (quoting United

States v. Master, 614 F.3d 236, 242 (6th Cir. 2010)). We thus join our sister circuits

in upholding the district court’s application of the good‐faith exception in this

case.

CONCLUSION

We have considered Eldred’s remaining arguments and deem them waived

or without merit. For the foregoing reasons, we AFFIRM the judgment of the

district court.

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