Amicus Curiae Brief — Okello T. Chatrie, Petitioner v. United States

No. 25-112

IN THE

Supreme Court of the United States

_______________

OKELLO T. CHATRIE,

v.

UNITED STATES OF AMERICA,

_______________

Petitioner,

Respondent.

ON WRIT OF CERTIORARI TO THE

UNITED STATES COURT OF APPEALS

FOR THE FOURTH CIRCUIT

_______________

BRIEF OF IOWA, MICHIGAN, 29 STATES

AND THE DISTRICT OF COLUMBIA AS

AMICI CURIAE IN SUPPORT OF

RESPONDENT

_______________

BRENNA BIRD

DANA NESSEL

Attorney General of

Attorney General of

Iowa

Michigan

ERIC WESSAN

ANN M. SHERMAN

Solicitor General

Solicitor General

Counsel of Record

1305 E Walnut Street

P.O. Box 30212

Des Moines, IA 50319

Lansing, MI 48909

(515) 823- 9117

(517) 335-7628

eric.wessan@ag.iowa.gov

ShermanA@michigan.gov

Counsel for Amici Curiae

[additional signatories listed at the end of the brief]

i

TABLE OF CONTENTS

QUESTION PRESENTED ..................................... i

TABLE OF CONTENTS ......................................... i

TABLE OF AUTHORITIES................................. iii

INTEREST OF AMICUS CURIAE ....................... 1

SUMMARY OF ARGUMENT ................................ 3

ARGUMENT .......................................................... 4

I. The Fourth Amendment Question Turns on

Particularity And Discretion, Not A

Technology Category. .................................. 4

A. The Fourth Amendment’s historical

target is discretionary rummaging in

searches;

particularity

is

the

preventative doctrinal tool..................... 4

B. Geofence warrants are conceptually

closer to traditional warrant practice

than to long-term tracking. ................... 8

C. Carpenter does not establish a

categorical rule prohibiting collecting

location data. ........................................ 11

D. Bystander effects do not render a

properly

tailored

warrant

unconstitutional, and suppression is not

a proper remedy for third-party

generalized grievances. ........................ 13

II. States’

Sovereign

Interests

And

Administrability

Counsel

Against

A

Categorical Rule. ....................................... 15

A. Categorical bans impair state law

enforcement investigations. ................. 16

ii

B. A categorical ban incentivizes more

intrusive investigative methods. ......... 18

C. The traditional warrant standard

provides an administrable framework.18

CONCLUSION ..................................................... 20

ADDITIONAL COUNSEL ..................................... 2

iii

TABLE OF AUTHORITIES

Cases

Alderman v. United States,

394 U.S. 165 (1969) ................................................ 15

Andresen v. Maryland,

427 U.S. 463 (1976) ................................................ 13

Boyd v. United States,

116 U.S. 616 (1886) .................................................. 5

Camara v. Municipal Court of San Francisco,

387 U.S. 523 (1967) ........................................ 6, 7, 14

Carpenter v. United States,

585 U.S. 296 (2018) .............................. 2, 5, 8, 11, 12

Groh v. Ramirez,

540 U.S. 551 (2004) .................................................. 5

Illinois v. Gates,

462 U.S. 213 (1983) .............................................. 3, 9

Illinois v. Lidster,

540 U.S. 419 (2004) ............................................ 7, 12

Kyllo v. United States,

533 U.S. 27 (2001) .............................................. 8, 11

Maryland v. Garrison,

480 U.S. 79 (1987) .................................. 6, 13, 14, 15

People v. Meza,

90 Cal. App. 5th 520 (2023) ................................... 10

Price v. Superior Court,

93 Cal. App. 5th 13 (2023) ..................................... 10

Rakas v. Illinois,

439 U.S. 128 (1978) ................................................ 15

Riley v. California,

573 U.S. 373 (2014) .............................................. 2, 5

Stanford v. Texas,

379 U.S. 476 (1965) .............................................. 4, 5

United States v. Chatrie,

590 F. Supp. 3d 901 (E.D. Va. 2022) ..................... 10

iv

United States v. Chatrie,

136 F.4th 100 (4th Cir. 2025) ................ 9, 10, 12, 14

United States v. Jones,

565 U.S. 400 (2012) ............................................ 8, 11

United States v. Knotts,

460 U.S. 276 (1983) ................................................ 12

United States v. Rhine,

652 F. Supp. 3d 38 (D.D.C. 2023) .......................... 10

Uwazurike v. Jobes,

4:24-cv-00146-RGE-SBJ (S.D. Iowa Nov. 5, 2025) 16

United States v. Smith,

110 F.4th 817 (5th Cir. 2024) .................... 10, 12, 14

Zurcher v. Stanford Daily,

436 U.S. 547 (1978) .................................. 7, 8, 13, 15

Statutes

U.S. Const. amend. IV ................................................. 5

Other Authorities

Akhil Reed Amar, Fourth Amendment First

Principles, 107 Harv. L. Rev. 757 (1994) ................ 6

1

INTEREST OF AMICUS CURIAE

Amici curiae States of Iowa, Michigan, and the

States of Alabama, Alaska, Arizona, Arkansas, the

District of Columbia, Georgia, Kansas, Louisiana,

Maryland, Maine, Mississippi, Missouri, Nebraska,

New Jersey, New Mexico, New York, North Carolina,

Ohio, Oklahoma, Pennsylvania, South Carolina,

South Dakota, Tennessee, Texas and Washington

(“Amici States”) submit this brief in support of

Respondent United States and urge this Court to

affirm the judgment of the United States Court of

Appeals for the Fourth Circuit.

Modern technology has transformed criminal

investigations. New tools allow law enforcement to

identify perpetrators and secure convictions in cases

that only a decade ago might have remained unsolved.

One such tool is the geofence warrant, like the

warrant issued by a Virginia magistrate judge in this

case. Geofence warrants are judicially supervised tools

that allow law enforcement to obtain location-history

information from third-party providers tied to a

specific geographic area and time window.

Investigators typically seek this information when a

crime has occurred at a known location but the

perpetrator is unknown. By identifying devices

present at the scene during the relevant period, these

warrants help investigators generate leads and

identify suspects who would otherwise remain

unknown. In practice, geofence warrants have become

an important investigative tool for law enforcement,

particularly in cases where traditional methods yield

few leads or where perpetrators leave little physical

evidence.

When supported by probable cause and

appropriately tailored, geofence warrants can be more

2

precise than many traditional investigative methods.

Nothing in the Fourth Amendment prohibits courts

from authorizing warrants limited to time and place.

The warrant process provides the traditional check by

a neutral magistrate on governmental overreach

through the familiar requirements of probable cause,

particularity, and reasonableness.

Amici States have a strong interest in both

respecting the constitutional rights of their citizens

and ensuring that law enforcement has the tools

needed to keep those citizens safe. States routinely

investigate and prosecute criminal activity and

depend on stable, predictable Fourth Amendment

doctrine to guide officers in the field and courts

adjudicating suppression issues.

Amici States, as their sovereigns’ chief law

enforcement officers, also have an institutional

interest in the faithful application of this Court’s

Fourth Amendment precedents. This Court has

repeatedly recognized that digital tools capable of

revealing information about individuals’ movements

and associations demand careful constitutional

scrutiny. See Carpenter v. United States, 585 U.S. 296,

305–06 (2018); Riley v. California, 573 U.S. 373, 393–

97 (2014). Clarifying that properly tailored geofence

warrants may satisfy traditional Fourth Amendment

requirements will assist States in developing lawful

investigative practices that protect both privacy and

public safety.

Finally, States have a sovereign interest in

preserving constitutional rules that are both clear and

balanced. Uncertainty in Fourth Amendment doctrine

serves neither individual rights nor effective law

enforcement. The traditional warrant framework—

requiring probable cause, particularity, and prior

3

judicial approval—strikes the proper balance. This

Court should affirm that this framework applies to

geofence warrants.

SUMMARY OF ARGUMENT

Geofence warrants are a modern investigative tool

used to identify unknown perpetrators tied to a

specific place and time. Courts across the country are

now grappling with how to apply traditional Fourth

Amendment principles to that new technology. This

Court should make clear that the Constitution does

not categorically ban those investigative methods.

Instead, longstanding doctrine requires courts to

evaluate whether a warrant is supported by probable

cause, sufficiently particular, and reasonably

executed.

Petitioner seeks a sweeping constitutional rule

treating geofence warrants as categorically invalid.

But that approach conflicts with this Court’s

precedents and risks severe consequences for public

safety. The Fourth Amendment does not regulate

technology categories; it regulates law enforcement’s

conduct through requirements of probable cause,

particularity, and reasonableness. See Illinois v.

Gates, 462 U.S. 213, 236 (1983); Riley, 573 U.S. at 386.

Two principles should guide the Court’s resolution

of this case. First, new investigative techniques do not

conflict with the Fourth Amendment’s prohibition of

general warrants. The constitutional inquiry turns on

whether specific warrants satisfy traditional

requirements, including warrants issued using new

technologies. Second, a categorical ban on warrants

limited to the time and place of criminal activity would

harm States’ sovereign interests in public safety by

eliminating a judicially supervised tool that can be

more precise than traditional alternatives.

4

States have a vital interest in exercising their

police powers to protect residents and solve crimes.

Geofence warrants do just that—and law enforcement

agencies across the country use them responsibly,

subject to judicial oversight. These warrants involve

ample judicial process to ensure that constitutional

rights are respected.

This Court should affirm the en banc Fourth

Circuit’s judgment and decline to adopt a categorical

rule against geofence warrants—a rule that would be

untethered from the Fourth Amendment’s history,

doctrine, and practical realities.

ARGUMENT

I.

THE FOURTH AMENDMENT QUESTION TURNS

ON PARTICULARITY AND DISCRETION, NOT A

TECHNOLOGY CATEGORY.

This Court has repeatedly grounded Fourth

Amendment analysis in two foundational principles:

(1) warrants are constitutionally favored, and (2) the

“general warrant,” which leaves too much to executive

discretion, is the core constitutional vice to be avoided.

See Stanford v. Texas, 379 U.S. 476, 485–86

(1965); Carpenter, 585 U.S. at 303–05. That

framework properly governs geofence warrants. The

relevant inquiry for determining the constitutionality

of “geofence” warrants is whether the warrants are

supported by probable cause and meaningfully limits

what the government may obtain and do.

A. The Fourth Amendment’s historical target

is discretionary rummaging in searches;

particularity is the preventative doctrinal

tool.

5

The Fourth Amendment requires warrants to issue

with probable cause and to “particularly describ[e] the

place to be searched, and the persons or things to be

seized.” U.S. Const. amend. IV. That particularity

command seeks to prevent general warrants—

authorizations that leave too much to the discretion of

the officer executing the warrant. See Stanford, 379

U.S. at 485–86; see also Groh v. Ramirez, 540 U.S.

551, 557–58 (2004).

General warrants were objectionable not because

they authorized searches that might incidentally

affect multiple persons, but because they vested openended discretionary power in executive officers

untethered to judicially defined limits. English and

colonial practices, like writs of assistance, permitted

officials to search broadly for evidence without

meaningful constraints, often authorizing entry into

any house or premises at the officer’s choosing and

without particularized justification. See Stanford, 379

U.S. at 481–85. Those instruments were reviled

because they enabled officers to conduct exploratory

rummaging in search of evidence without neutral

oversight. Id. at 482.

The Fourth Amendment was designed to eliminate

such arbitrary executive authority. See Boyd v. United

States, 116 U.S. 616, 625–30 (1886) (tracing the

Amendment’s origins to opposition to general

warrants and writs of assistance); Riley, 573 U.S. at

403 (same); Carpenter, 585 U.S. at 303–05 (same).

Colonial opposition to writs of assistance reflected the

Founding generation’s concern with searches that

vested broad, discretionary authority in executive

officers. See Stanford, 379 U.S. at 481 (1965).

Historical scholarship confirms that the central

evil the Fourth Amendment was enacted to remedy

6

was the delegation of discretionary search authority to

executive officers without prior judicial limitation. See

Akhil Reed Amar, Fourth Amendment First

Principles, 107 Harv. L. Rev. 757, 771–76 (1994);

William J. Cuddihy, The Fourth Amendment: Origins

and Original Meaning, 602–1791, 770 (Oxford Univ.

Press 2009) (referring to general warrants as the

“overriding threat to privacy” during the founding

era).

The Framers responded to that central evil by

requiring a prior judicial authorization defining the

scope of a search through probable cause and

particular description, thereby transferring control

from the police officer to the magistrate and

preventing discretionary rummaging. See Maryland

v. Garrison, 480 U.S. 79, 84 (1987).

Properly tailored geofence warrants bear little

resemblance to the historical general warrants the

Fourth Amendment was designed to forbid. Rather

than authorizing exploratory searches wherever

officers choose to look, geofence warrants are anchored

to judicially approved constraints: a defined

geographic area, a defined time window, and a defined

investigative objective supported by probable cause.

The magistrate—not the police officer—approves

those parameters in advance. Geofence warrants also

typically employ a staged disclosure process in which

the provider first produces anonymized device

identifiers within the defined area and time window,

and investigators must make additional justified

requests before any identifying information is

disclosed.

This Court’s precedent confirms that the Fourth

Amendment permits warrants affecting multiple

unknown persons so long as neutral judicial standards

7

reasonably constrain the search. In Camara v.

Municipal Court of San Francisco, the Court held that

administrative inspection programs authorizing areawide searches could satisfy the Fourth Amendment

even though they affected occupants not suspected of

wrongdoing. 387 U.S. 523, 534–39 (1967).

This Court explained that probable cause in that

context may rest on “reasonable legislative or

administrative standards” rather than individualized

suspicion as to each affected person, provided that a

neutral magistrate defines the scope of the search in

advance.

Id.

at

538.

The

principle

underlying Camara is directly relevant here: the

Fourth Amendment’s core protection lies in judicially

imposed limits on executive discretion, not in a

requirement that every affected individual be

identified beforehand. Properly structured geofence

warrants operate within the same basic framework by

tying the search to objective criteria—place, time, and

investigative purpose—approved in advance by a

magistrate.

That a warrant may initially implicate unknown

persons does not render it “general.” Warrants have

long been permitted to obtain evidence from third

parties and to affect persons not yet identified so long

as the search remains particularized and tethered to

the offense under investigation. See Zurcher v.

Stanford Daily, 436 U.S. 547, 555–56 (1978) (“the

State’s interest in enforcing the criminal law and

recovering evidence is the same whether the third

party is culpable or not”). Cf. Illinois v. Lidster, 540

U.S. 419, 427 (2004) (affirming an investigative stop

where “the police appropriately tailored their

checkpoint stops to fit important criminal

investigatory needs” to assist in “find[ing] the

8

perpetrator of a specific and known crime,” i.e., a hitand-run accident resulting in a death). The

constitutional inquiry therefore turns on whether the

warrant meaningfully limits government discretion,

not whether it touches multiple individuals. When

judicial supervision defines the scope of the search in

advance—as with a properly structured geofence

warrant—the historical concerns animating the

Fourth Amendment are satisfied.

That same principle applies even when a warrant

seeks evidence from a third-party custodian. Warrants

frequently involve third parties and may involve

initially unknown persons. After all, the Fourth

Amendment demands reasonable tailoring, not preidentification

of

every

affected

individual.

See Zurcher, 436 U.S. at 555–56. The constitutional

question is whether the warrant’s terms and execution

procedures cabin discretion and maintain a nexus to

the offense.

B. Geofence warrants are conceptually

closer to traditional warrant practice than

to long-term tracking.

This Court has repeatedly confronted new

investigative technologies by applying traditional

Fourth Amendment principles rather than imposing

categorical bans on new technologies that may have

different scopes than other traditional mechanisms to

engage in searches. See Kyllo v. United States, 533

U.S. 27 (2001) (thermal imaging technology); United

States v. Jones, 565 U.S. 400 (2012) (GPS tracking);

Carpenter v. United States, 585 U.S. 296 (2018)

(historical cell-site location information). Those

decisions reflect a consistent approach: courts

9

evaluate the scope of government authority and the

limits imposed by the warrant process rather than

invalidating investigative tools that rely on emerging

technologies. Geofence warrants should be evaluated

under the same framework.

Geofence warrants are typically used when a crime

occurs at a known location but the perpetrator is

unknown. This brief addresses the situation in which

such a warrant is sought and received, as it was in this

case—it does not address the question as to whether

such warrants are constitutionally required. But when

such a warrant is sought, it is “practical,

commonsense” to infer that the perpetrator was

physically present at the crime scene and that

evidence identifying devices present during that

discrete window may bear a nexus to the offense.

Gates, 462 U.S. at 238. That inference does not convert

the warrant into a dragnet. Rather, it provides the

nexus that makes the request reasonable so long as

the warrant is narrowly bounded in space and time

and includes procedures designed to limit the

exposure of irrelevant information.

A geofence warrant is a form of reverse-location

search warrant that compels a service provider to

disclose information about devices present within a

defined geographic area during a specified time

window. As one judge below explained, such a warrant

“requires a service provider to produce location data

from cell phone users who were near the scene when a

crime occurred.” United States v. Chatrie, 136 F.4th

100, 102 (4th Cir. 2025) (Diaz, J., concurring).

When law enforcement obtains a geofence warrant,

the warrant must specify both the geographic

boundary and the temporal window associated with

the offense. In this case, the detective drew a geofence

10

with a 150-meter radius in an urban environment and

sought data for devices present within that area for a

one-hour period. Id. at 103.

Service providers typically respond to geofence

warrants through a structured three-step process. Id.

at 102–03. At the first step, the provider searches its

location-history

database

and

produces

an

anonymized list of devices—identified only by

pseudonymous numbers—whose location points fall

within the geofence. The provider returns associated

location coordinates and timestamps for each device.

Id.; see also United States v. Smith, 110 F.4th 817,

824–25 (5th Cir. 2024).

At the second step, investigators may request

additional location-history information for a smaller

subset of devices identified during the initial review.

This step does not expand the search; instead, it

allows investigators to determine whether particular

devices moved in ways consistent with the crime while

narrowing the pool of devices under consideration. See

United States v. Chatrie, 136 F.4th at 103.

At the third step, after investigators identify the

most relevant devices, the provider may disclose

subscriber information associated with those

accounts. Id. This step reveals identifying information

only after the dataset has been twice narrowed.

This staged disclosure process limits unnecessary

exposure of information about uninvolved individuals

by requiring progressive narrowing before any

identifying information is produced. Investigators

thus “attempt to narrow down the list of users for

which the government would obtain the most invasive

information.” Id. (quoting United States v. Chatrie,

590 F. Supp. 3d 901, 918 (E.D. Va. 2022)).

11

Courts analyzing geofence warrants have therefore

focused on whether the warrant’s geographic,

temporal, and procedural limits sufficiently constrain

executive discretion. See United States v. Rhine, 652

F. Supp. 3d 38, 73–89 (D.D.C. 2023); People v. Meza,

90 Cal. App. 5th 520, 537–40 (2023); Price v. Superior

Court, 93 Cal. App. 5th 13, 27–30 (2023).

Properly structured geofence warrants therefore

bear little resemblance to the sweeping general

warrants the Fourth Amendment forbids. Instead,

they operate through a constrained process that

narrows a dataset tied to a specific crime scene and

time window before identifying individuals. The

Constitution does not forbid such warrants

categorically.

C. Carpenter does not establish a categorical

rule prohibiting collecting location data.

This Court in Carpenter v. United States held that

acquiring an extended span of historical cell-site

location information (CSLI) constituted a search,

emphasizing how such data enables “near perfect

surveillance” and a “detailed chronicle of a person’s

physical presence compiled every day, every moment,

over several years.” 585 U.S. at 309–10 (internal

quotation marks omitted). The Court’s reasoning built

upon earlier technological-surveillance decisions

recognizing that the Fourth Amendment must adapt

to new investigative tools without abandoning its

traditional analytical framework. See United States v.

Jones, 565 U.S. 400, 404–05 (2012); Kyllo v. United

States, 533 U.S. 27, 34–35 (2001).

But the Court also emphasized the narrowness of

its holding and declined to “call into question” other

investigative

techniques

involving

digital

12

data. Carpenter, 585 U.S. at 316–17. Those decisions

confirm that the constitutional inquiry turns on the

scope and intrusiveness of the surveillance

technique—not on the type of digital technology

involved.

Geofence warrants differ in both purpose and

structure from the long-term tracking at issue

in Carpenter. They are designed to identify unknown

perpetrators tied to a specific crime occurring at a

known place and time, not to follow a known

individual’s movements for weeks or months. Cf.

Lidster, 540 U.S. at 427 (investigative stop

permissible where officers sought information to

identify the perpetrator of “a specific and known

crime”).

That framework reflects this Court’s recognition

that movements in public ordinarily carry reduced

expectations of privacy. See United States v. Knotts,

460 U.S. 276, 281–82 (1983); Carpenter, 585 U.S. at

309–10. Geofence warrants operate within those

principles. They are limited to a short window

surrounding a specific crime scene and typically

involve a staged narrowing process before any

identifying information is produced. Service providers

first return anonymized device identifiers within the

defined area and time window, and investigators must

make additional justified requests before any

identifying information is disclosed. See Chatrie, 136

F.4th at 102–03 (Diaz, J., concurring); United States v.

Smith, 110 F.4th 817, 824–25 (5th Cir. 2024).

Unlike the prolonged tracking at issue

in Carpenter, such warrants identify devices present

at a particular place and time rather than

reconstructing a person’s movements over months or

years. Properly tailored geofence warrants therefore

13

resemble

traditional

investigative

techniques

designed to identify unknown perpetrators at a crime

scene—not the sweeping, long-term surveillance that

concerned the Court in Carpenter.

D. Bystander effects do not render a properly

tailored warrant unconstitutional, and

suppression is not a proper remedy for

third-party generalized grievances.

The fact that a search may incidentally reveal

information about individuals not suspected of

wrongdoing does not transform a warrant into a

general warrant. Law enforcement routinely

encounters information about innocent people when

executing otherwise lawful warrants.

For example, when officers execute a warrant to

search a home, they may encounter roommates, family

members, or guests who are not themselves suspected

of wrongdoing. Likewise, searching a residence may

expose the private effects of individuals who are not

targets of the investigation. Warrants for business

records may reveal information about customers or

associates who have no connection to criminal activity.

See Zurcher, 436 U.S. at 555–56 (recognizing that

searches for evidence may be conducted at premises of

third parties not suspected of wrongdoing); Garrison,

480 U.S. at 84 (lawful searches may incidentally affect

persons not suspected of criminal activity); Andresen

v. Maryland, 427 U.S. 463, 482 n.11 (1976)

(recognizing that searches for papers necessarily

require examination of some innocuous documents).

The Fourth Amendment has never required

investigative methods that reveal information only

about guilty parties and no one else.

14

The constitutional inquiry instead focuses on

whether the warrant is supported by probable cause

and sufficiently tailored to limit executive discretion.

That principle is particularly important where, as

here, investigators seek to identify unknown

perpetrators tied to a specific crime committed at a

known place and time. The Fourth Amendment has

long tolerated warrants that may initially implicate

individuals not suspected of wrongdoing so long as the

search remains particularized and tethered to the

offense under investigation.

This Court’s precedents likewise recognize that

lawful searches may incidentally affect innocent third

parties. In Maryland v. Garrison, for example, the

Court explained that officers executing a valid

warrant may encounter circumstances affecting

individuals beyond the original target of the search

without

thereby

rendering

the

search

unconstitutional. 480 U.S. at 84. Similarly, in Camara

v. Municipal Court, the Court recognized that certain

warrant-authorized

inspections

may

involve

individuals not suspected of criminal wrongdoing yet

remain reasonable where the search is governed by

neutral judicial standards. 387 U.S. at 534–39.

The same structural logic applies to geofence

warrants. Properly tailored geofence warrants do not

authorize exploratory rummaging. Instead, they begin

with a dataset tied to a defined geographic area and

time window associated with a specific crime. Service

providers initially return anonymized device

identifiers, and investigators must make additional

justified requests before any identifying information is

disclosed. See Chatrie, 136 F.4th at 102–03 (Diaz, J.,

concurring); Smith, 110 F.4th at 824–25. This staged

narrowing process reduces the exposure of irrelevant

15

information and limits identification of individuals

until investigative relevance is established.

Fourth Amendment rights are also personal.

Remedies such as suppression turn on whether the

defendant’s own constitutional rights were violated,

not on generalized concerns about the privacy

interests of others. See Rakas v. Illinois, 439 U.S. 128,

133–34 (1978); Alderman v. United States, 394 U.S.

165, 174 (1969). A defendant therefore cannot

invalidate an otherwise particularized warrant by

invoking the hypothetical privacy interests of

unknown third parties.

Nor does the fact that a warrant may initially

collect information affecting individuals not suspected

of wrongdoing render it an unconstitutional general

warrant. Courts have long recognized that lawful

searches may incidentally affect third parties when

officers seek evidence tied to a particular offense.

See Garrison, 480 U.S. at 84; Zurcher, 436 U.S. at

559–60. The constitutional inquiry instead focuses on

whether the warrant meaningfully constrains

executive discretion and remains tethered to the crime

under investigation.

For these reasons, the possibility that a geofence

warrant may initially capture information about

uninvolved individuals does not render the warrant

unconstitutional. When the warrant is supported by

probable cause, limited in time and place, and

structured to narrow the dataset before identifying

individuals, the Fourth Amendment’s protections

against general warrants remain fully satisfied.

II.

STATES’ SOVEREIGN INTERESTS

AND

ADMINISTRABILITY COUNSEL AGAINST A

CATEGORICAL RULE.

16

States

bear

primary

responsibility

for

investigating and prosecuting criminal activity within

their borders. In doing so, state law enforcement

officers rely on the Fourth Amendment’s established

warrant framework—probable cause, particularity,

and judicial supervision—to ensure that investigative

tools are used in a manner consistent with

constitutional protections. A categorical rule

forbidding geofence warrants would disrupt that

framework and interfere with States’ ability to

investigate crimes while still protecting individual

rights.

A. Categorical bans impair

enforcement investigations.

state

law

When a crime occurs at a known place and time but

the perpetrator is unknown, geofence warrants can be

one of the few investigative tools capable of generating

leads while remaining subject to judicial supervision

from the outset. That is especially true for offenses in

which perpetrators have limited connections to known

victims, act quickly, or leave minimal physical

evidence.

Recent experience confirms that States are already

employing location-based investigative techniques in

precisely this targeted, crime-specific manner. For

example, litigation arising from a state sportswagering investigation in Iowa involved geolocation

filtering tools used to identify devices present within

defined athletic facilities during specified periods,

followed by additional legal process to determine

whether identified individuals were engaged in

unlawful conduct. According to the pleadings,

investigators filtered device data associated with

17

wagering applications at sports facilities and then

issued subpoenas seeking identifying information tied

to those devices. See Uwazurike v. Jobes, No. 4:24-cv00146-RGE-SBJ, Dkt. 89 at 2 (S.D. Iowa Nov. 5, 2025).

Other investigations likewise demonstrate how

geofence warrants can generate critical leads when

perpetrators are otherwise unknown. In People v.

Handrich, No. 22-10584-FC (Mich. Cir. Ct. Dec. 18,

2023), investigators used a geofence warrant during a

homicide investigation in Mecosta County, Michigan.

The victim, Ashley Godfrey, had been strangled and

beaten to death and her body concealed in a wooded

area, and there were no eyewitnesses to the crime.

Investigators obtained a geofence warrant covering

the wooded area during the relevant time window and

followed the provider’s staged disclosure process. The

resulting location-history data revealed that the

defendant’s device was present in the wooded area at

the time of the homicide—and that no other device

appeared within the geofence during that period. That

information placed the defendant at the crime scene

and corroborated other evidence obtained during the

investigation, including his admission that he caused

the victim’s death. A jury subsequently convicted the

defendant of first-degree murder.

Judicial consideration of these investigations

illustrates how courts already evaluate location-based

investigative techniques under traditional Fourth

Amendment principles rather than imposing

categorical prohibitions based solely on the technology

used. When suspects are unknown but suspected

wrongdoing is tied to a specific place and time,

location-based data can provide one of the narrowest

available tools for generating investigative leads while

18

remaining subject to judicial supervision from the

start.

A constitutional rule prohibiting geofence

warrants would disrupt investigations operating

within the warrant framework and force reliance on

less precise alternatives. The Fourth Amendment has

never required that result.

B. The

traditional

warrant

standard

provides an administrable framework.

Magistrate judges evaluate warrant applications

every day. The Fourth Amendment’s familiar

requirements—probable cause, particularity, and

reasonableness—provide workable standards for

evaluating geofence warrants just as they do for other

searches.

A categorical rule triggered merely by the use of a

particular technology would depart from that

framework. Some geofence warrants may be narrowly

tailored to minimize intrusion on third parties, while

other investigative techniques that do not involve

geofencing could operate far more broadly.

By contrast, applying traditional warrant

principles allows courts to tailor searches to the

circumstances of a particular investigation.

Magistrates may shorten the relevant time window,

narrow the geographic search area, limit the

categories of data sought, require staged disclosure

procedures that delay identification of individuals

until investigative relevance is established, impose

retention limits, or require renewed judicial

authorization before expanding the search.

This scope-based approach aligns with the Fourth

Amendment’s historical focus on limiting executive

19

discretion while preserving the warrant process that

the Constitution favors.

20

CONCLUSION

This Court should affirm the Fourth Circuit

Court’s judgment.

Respectfully submitted,

BRENNA BIRD

Attorney General

State of Iowa

DANA NESSEL

Attorney General

State of Michigan

ERIC H. WESSAN

Solicitor General

Counsel of Record

1305 E Walnut Street

Des Moines, IA 50319

(515) 823- 9117

eric.wessan@ag.iowa.gov

ANN M. SHERMAN

Solicitor General

Dated: APRIL 1, 2026

P.O. Box 30212

Lansing, MI 48909

(517) 335-7628

ShermanA@michigan.gov

21

ADDITIONAL LEGAL

REPRESENTATIVES OF STATES

Steve Marshall

Attorney General of

Alabama

Kris Kobach

Attorney General of

Kansas

Stephen J. Cox

Attorney General of

Alaska

Liz Murrill

Attorney General of

Louisiana

Kris Mayes

Attorney General of

Arizona

Anthony G. Brown

Attorney General of

Maryland

Tim Griffin

Attorney General of

Arkansas

Aaron M. Frey

Attorney General of

Maine

Brian L. Schwalb

Attorney General of

the District of

Columbia

Keith Ellison

Attorney General of

Minnesota

Chris Carr

Attorney General of

Georgia

Kwame Raoul

Attorney General of

Illinois

Theodore E. Rokita

Attorney General of

Indiana

Lynn Fitch

Attorney General of

Mississippi

Catherine Hanaway

Attorney General of

Missouri

Austin Knudsen

Attorney General of

Montana

22

Michael T. Hilgers

Attorney General of

Nebraska

Marty Jackley

Attorney General of

South Dakota

Jennifer Davenport

Attorney General of

New Jersey

Jonathan Skrmetti

Attorney General of

Tennessee

Raúl Torrez

Attorney General of

New Mexico

Ken Paxton

Attorney General of

Texas

Letitia James

Attorney General of

New York

Derek E. Brown

Attorney General of

Utah

Jeff Jackson

Attorney General of

North Carolina

Nicholas W. Brown

Attorney General of

Washington

Dave Yost

Attorney General of

Ohio

Gentner Drummond

Attorney General of

Oklahoma

Dave Sunday

Attorney General of

Pennsylvania

Alan Wilson

Attorney General of

South Carolina