Amicus Curiae Brief — William Trevor Case, Petitioner v. Montana

Supreme Court briefAug 6, 2025

Ask Donna

What actually matters in this document.

Text

No. 24-624

In the Supreme Court of the United States

WILLIAM TREVOR CASE, Petitioner,

MONTANA

On Writ of Certiorari to the

Supreme Court of Montana

BRIEF OF PROJECT FOR PRIVACY &

SURVEILLANCE ACCOUNTABILITY

AND RESTORE THE FOURTH, INC.

AS AMICI CURIAE SUPPORTING PETITIONER

MAHESHA P. SUBBARAMAN

SUBBARAMAN PLLC

80 S. 9th Street, Suite 900

Minneapolis, MN 55402

(612) 315-9210

mps@subblaw.com

GENE C. SCHAERR

Counsel of Record

ERIK S. JAFFE

JOSHUA J. PRINCE

JUSTIN A. MILLER

AARON C. WARD

SCHAERR | JAFFE LLP

1717 K Street NW

Suite 900

Washington, DC 20006

(202) 787-1060

gschaerr@schaerr-jaffe.com

Counsel for Amici Curiae

AUGUST 6, 2025

QUESTION PRESENTED

Whether law enforcement may enter a home

without a search warrant based on less than probable

cause that an emergency is occurring, or whether the

emergency-aid exception requires probable cause.

TABLE OF CONTENTS

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

TABLE OF AUTHORITIES ....................................... iv

INTRODUCTION AND INTERESTS OF

AMICI CURIAE ..................................................... 1

STATEMENT .............................................................. 3

SUMMARY .................................................................. 4

ARGUMENT ................................................................ 5

Founding-era Expectations of Privacy

Required at Least Probable Cause of Exigent

or Emergency Circumstances for Warrantless

Home Entry, Even in Emergencies. ..................... 6

A. Founding-era common law sets the

expectations and standards for resolving

modern Fourth Amendment questions. ......... 6

B. At common law, officers could enter a

home without a warrant only to arrest a

fleeing felon, if they witnessed an affray,

or upon observable proof they could

prevent imminent harm. ................................ 8

II. If the Evidentiary Threshold for the

Emergency-Aid Exception Were Lowered, It

Could Easily Be Used to Justify Extensive

Warrantless Electronic Surveillance.................. 18

iii

A. Electronic surveillance raises the same

Fourth Amendment concerns as

warrantless home entry. .............................. 18

B. Absent a fixed rule of probable cause,

warrantless electronic surveillance could

become routine and severely compromise

Americans’ privacy. ...................................... 22

CONCLUSION .......................................................... 27

TABLE OF AUTHORITIES

Cases

Boyd v. United States,

116 U.S. 616 (1886) .................................................. 7

Brigham City v. Stuart,

547 U.S. 398 (2006) ................................................ 15

Brinegar v. United States,

338 U.S. 160 (1949) ................................................ 26

Cady v. Dombrowski,

413 U.S. 433 (1973) .......................................... 22, 26

Caniglia v. Strom,

593 U.S. 194 (2021) .............................. 1, 2, 3, 15, 17

Carpenter v. United States,

585 U.S. 296 (2018) .............................................. 4, 7

Carroll v. United States,

267 U.S. 132 (1925) .................................................. 7

Coolidge v. New Hampshire,

403 U.S. 443 (1971) ................................................ 26

Delafoile v. New Jersey,

24 A. 557 (N.J. 1892) ............................................. 14

Est. of Frazier v. Miller,

484 P.3d 912 (Mont. 2021) ..................................... 16

Florida v. Jardines,

569 U.S. 1 (2013) .................................................... 18

Free Speech Coal., Inc. v. Paxton,

145 S. Ct. 2291 (2025) ............................................ 21

Gardner v. New Jersey,

26 A. 30 (N.J. Sup. Ct. 1892) ................................. 13

Heidi Grp., Inc. v. Texas Health & Hum. Servs.

Comm’n, 138 F.4th 920 (5th Cir. 2025)................. 21

Kentucky v. King,

563 U.S. 452 (2011) ................................................ 26

Ker v. California,

374 U.S. 23 (1963) .................................................. 12

Lange v. California,

594 U.S. 295 (2021) .......................................... 1, 2, 4

McLennon v. Richardson,

81 Mass. 74 (1860) ................................................. 13

Michigan v. Fisher,

558 U.S. 45 (2009) .................................................. 15

Michigan v. Long,

463 U.S. 1032 (1983) .............................................. 17

Mincey v. Arizona,

437 U.S. 385 (1978) ................................................ 15

Montana v. Lovegren,

51 P.3d 471 (Mont. 2002) ............................... 2, 4, 16

N.Y. State Rifle & Pistol Ass’n, Inc.

v. Bruen, 597 U.S. 1 (2022) ................................ 4, 12

Payton v. New York,

445 U.S. 573 (1980) .................................................. 9

Reed v. Town of Gilbert,

576 U.S. 155 (2015) .................................................. 6

Riley v. California,

573 U.S. 373 (2014) ........................ 18, 19, 20, 21, 22

Semayne’s Case,

77 Eng. Rep. 194 (K.B. 1604)................................... 8

Terry v. Ohio,

392 U.S. 1 (1968) .............................................. 16, 17

United States v. Di Re,

332 U.S. 581 (1948) .................................................. 7

United States v. Heckenkamp,

482 F.3d 1142 (9th Cir. 2007) ................................ 24

United States v. Rahimi,

602 U.S. 680 (2024) ................................................ 12

United States v. Smith,

110 F.4th 817 (5th Cir. 2024) ................................ 23

United States v. Warshak,

631 F.3d 266 (6th Cir. 2010) .................................. 21

United States v. Zelaya-Veliz,

94 F.4th 321 (4th Cir. 2024) .................................. 21

Welsh v. Wisconsin,

466 U.S. 740 (1984) .................................................. 9

Constitutional Provision

U.S. Const. amend. IV ....................................... 1, 7, 17

Rule

Fed. R. Crim. P. 41 .................................................... 23

Treatises

William Blackstone,

Commentaries on the Laws of England

(1769) ...................................................................... 12

Richard Burn,

The Justice of the Peace, and Parish

Officer (28th ed. 1837) ........................................... 12

vii

Joseph Chitty,

A Practical Treatise on the Criminal Law

(London, A.J. Valpy 1816) ....................................... 9

Joseph Chitty,

A Practical Treatise on the Criminal Law

(Springfield, G & C Merriam 1836)....................... 11

Edward Coke,

The Fourth Part of the Institutes of the

Laws of England: Concerning the

Jurisdiction of Courts

(Flesher 1644) .......................................................... 9

Matthew Hale,

Historia Placitorum Coronae (The History

of the Pleas of the Crown)

(Little Britain, E. Rider 1800) ................................. 8

Matthew Hale,

Historia Placitorum Coronae (The History

of the Pleas of the Crown)

(Phila., Robert H. Small 1847) ........................ 10, 11

William Hawkins,

A Treatise of the Pleas of the Crown

(London, Eliz. Nutt 1716) ................................ 11, 12

Joseph Shaw,

The Practical Justice of the Peace

(London, Henry Lintot, 4th ed. 1744) ................... 10

Joseph Story,

Commentaries on the Constitution of the

United States (Boston, Hilliard, Gray & Co.

1833) ..................................................................... 7, 9

viii

Other Authorities

Black’s Law Dictionary (1st ed. 1891) ...................... 14

Br. of Project for Privacy & Surveillance

Accountability and Restore the Fourth, Inc.

as Amici Curiae Supporting Petitioner,

Lange v. California, 594 U.S. 295 (2021)

(No. 20-18) .............................................................. 10

Andrew Crocker,

FAQ: Apple, the FBI, and Zero Days,

Elec. Frontier Found. (Apr. 14, 2016) ................... 25

Laura K. Donohue,

The Original Fourth Amendment,

83 U. Chi. L. Rev. 1181 (2016)..................... 9, 10, 13

Government Hacking,

Privacy Int’l ............................................................ 24

Sasha Harris-Lovett,

In survey, 88% of U.S. adults said they had

sexted and 96% of them endorsed it,

L.A. Times (Aug. 8, 2015) ...................................... 19

Elizabeth Kinsey Hawley,

Sexting Felonies: A Major Problem for

Minors, Communicating Psych. Sci.

(Aug. 2020) ............................................................. 19

Internet, Broadband Fact Sheet,

Pew Rsch. Ctr. (Nov. 13, 2024) .............................. 21

Giles Jacobs,

The Law-Dictionary: Explaining the Rise,

Progress, and Present State, of the English

Law (Phila., I. Riley 1811) ..................................... 10

Nelson B. Lasson,

The History and Development of the Fourth

Amendment to the United States

Constitution (1937) .................................................. 8

Jonathan Mayer,

Government Hacking,

127 Yale L.J. 570 (2017) ........................................ 25

Mobile Fact Sheet,

Pew Rsch. Ctr. (Nov. 13, 2024) .............................. 20

Ellen Nakashima,

FBI paid professional hackers one-time fee

to crack San Bernardino iPhone,

Wash. Post (Apr. 12, 2016) .................................... 24

Amy Novotney,

A growing wave of online therapy,

48 Monitor on Psych. 48 (Feb. 2017) ............... 19, 20

George Orwell,

1984 (1949) ............................................................. 18

Press Release,

U.S. Census Bureau, No. CB24-TPS.61,

Computer and Internet Use in the United

States: 2021 (June 18, 2024) ................................. 20

Melinda Roberts,

Note, The Emergency Doctrine, Civil Search

and Seizure, and the Fourth Amendment,

43 Ford. L. Rev. 571 (1975) ................................... 15

William Sheppard,

The Offices and Duties of Constables

(London, Richard Hodgkinsonne 1641) ................. 13

Saunders Welch,

Observations on the Office of Constable

(London, printed for A. Millar 1754) ..................... 13

INTRODUCTION AND INTERESTS

OF AMICI CURIAE 1

In Caniglia v. Strom, 593 U.S. 194, 199 (2021), and

Lange v. California, 594 U.S. 295, 303 (2021), this

Court rejected Fourth Amendment analyses that

allowed the police to enter a person’s home without a

warrant absent a true exigency. In each case, the lower

court approved a non-exigent home entry by ignoring

founding-era, common-law home protections and

expanding a previously narrow exception to the Fourth

Amendment’s warrant requirement. The Montana

Supreme Court repeated those mistakes here,

approving police entry of a home to render emergency

aid even though there was no probable cause that an

emergency existed. On this view, police may enter a

home without a warrant even when a judge would

have to deny a warrant due to lack of probable cause

on the same grounds. See U.S. Const. amend. IV. The

decision below, no less than the lower court decisions

rejected in Caniglia and Lange, cannot be squared

with the Fourth Amendment and should be reversed.

Proper resolution of the question presented is of

paramount importance to Amici Project for Privacy &

Surveillance Accountability, Inc. and Restore the

Fourth, Inc. Both Amici are national, non-partisan

civil liberties organizations dedicated to robust

enforcement of the Fourth Amendment. Amici are

dedicated to preserving the Founders’ vision for

1 This brief was not authored in whole or in part by counsel for

any party and no person or entity other than amici curiae or their

counsel has made a monetary contribution to the brief’s

preparation or submission.

Americans’ privacy in the modern age, and the

decision below reflects a drastic departure from

founding-era understandings.

At common law, for example, absent the

homeowner’s consent, the government needed to

obtain a warrant before entering a person’s home in all

but the most extreme circumstances. Early common

law authorities set the constitutional floor for the

Fourth Amendment’s protection of the home from

warrantless searches.

Consistent with common-law history, this Court

requires “warrant exception[s] permitting home entry

[to be] jealously and carefully drawn” and regularly

“decline[s] to expand the scope of exceptions to the

warrant requirement to permit warrantless entry into

the home.” Lange, 594 U.S. at 303 (cleaned up). Yet the

Supreme Court of Montana condoned a warrantless

home entry here under its expansive version of the

very “community caretaker” exception this Court

rejected in Caniglia—just under a different name.

Under Montana’s exception, no warrant is needed to

enter a home if there are merely “articulable facts”—

falling well-short of probable cause—that an

emergency is ongoing. See Montana v. Lovegren, 51

P.3d 471, 475-476 (Mont. 2002). That standard should

be rejected because it fails to clear the minimum

founding-era privacy bar and threatens to dilute

Fourth Amendment protections in other areas—such

as searches of personal electronics.

STATEMENT

Police officers went to William Case’s home after

obtaining information suggesting that Case

threatened suicide. Looking through a window, the

police saw not Case, but an empty gun holster and a

notepad. App.4a. They thus decided not to enter,

believing that Case “was likely lying in wait * * * to

commit suicide by cop.” App.5a, 29a. The police waited

around forty minutes before entering Case’s home.

App.5a. When they finally entered, they did so without

a warrant: They felt unrestrained by the Fourth

Amendment because they believed they were there to

help Case. App.4a. While sweeping the house, one

officer saw a “dark object” “near Case’s waist,” believed

it was a gun, and shot Case, who fell. App.6a. Police

retrieved a gun from a nearby laundry hamper. Ibid.

Case was charged with felony assault on a peace

officer. Before trial, he moved unsuccessfully to

suppress the evidence obtained during the warrantless

search of his home. App.6a-7a, 43a. The Montana

Supreme Court affirmed, holding that Montana’s

“community caretaker” exception justified the

warrantless entry notwithstanding Caniglia. App.18a20a. The court did little to address Case’s showing that

there was no exigency since police entered Case’s home

knowing that he was likely trying to commit “suicide

by cop.” In dissent, Justice McKinnon noted that—by

condoning the search here despite the lack of probable

cause—the majority had extended Montana’s

exception to circumstances this Court expressly

rejected in Caniglia. App.27a-28a (McKinnon, J.,

dissenting).

SUMMARY

The Supreme Court of Montana maintains that

police need not obtain a warrant to enter a home when

“an experienced officer would suspect that a citizen is

in need of help” considering “specific” and “articulable”

facts. App.16a (quoting Montana v. Lovegren, 51 P.3d

471, 475-476 (Mont. 2002)). Articulable suspicion of an

emergency, however, is not the same as probable cause

to believe an emergency exists—a more exacting rule.

The decision below thus explodes a narrow Fourth

Amendment exception allowing warrantless home

entry in cases of true emergency. Because this holding

defies common-law privacy expectations and this

Court’s precedent, it should be reversed.

I. When considering claimed exceptions to the

Fourth Amendment, this Court looks to founding-era,

common-law expectations of privacy and the original

public meaning of the Fourth Amendment. Carpenter

v. United States, 585 U.S. 296, 304-305 (2018); Lange,

594 U.S. at 309; cf. N.Y. State Rifle & Pistol Ass’n, Inc.

v. Bruen, 597 U.S. 1, 22-24 (2022). No founding-era or

common-law authority of which Amici are aware

would have allowed the police to enter a person’s home

for community-caretaking or emergency-aid purposes

based on only the permissive standard of “articulable

suspicion.” To the contrary, the home was so sacred at

common law that, absent a warrant or consent, the

government could enter it only in the most extreme

circumstances. Such historical unwillingness to allow

warrantless searches, even when in furtherance of

some suspected public benefit, supports requiring

probable cause to believe that an emergency exists

before the police may undertake a warrantless entry.

The Court should reject the lower court’s expansive

understanding of the emergency-aid requirement for

this reason.

II. Lowering the bar for emergency-aid searches

also risks the loss of Fourth Amendment protections in

other sensitive contexts—especially the digital arena.

Electronic devices and accounts hold vast amounts of

personal information that historically would have

been found only in the home. By the same token, these

sources—no less than the home itself—may harbor

suspected emergencies (however improbable). That

poses a problem. If the Court were to lower the burden

of proof to justify warrantless searches of the home, it

would, in turn, open the door to warrantless searches

of less historically protected areas like electronic

devices and accounts, producing a devastating loss of

privacy for all Americans. The Court should reject the

lower court’s understanding of the Fourth Amendment

for this reason too.

ARGUMENT

Amici agree with Petitioner (at 19-28) that the

decision below conflicts with this Court’s Fourth

Amendment precedent. Articulable suspicion of an

emergency cannot suffice to enter a home without a

warrant—a reality that founding-era law governing

warrantless entry of homes makes clear. Also, if the

standard adopted below were applied to electronic

devices or accounts, digital privacy would all but

disappear. To prevent these harms, the Court should

reverse. Homes—and, by logical extension, electronic

devices and accounts carrying all the information of a

home—merit the constitutional protection of probable

cause when confronted with warrantless searches

executed by the police in the name of emergency aid.

Founding-era Expectations of Privacy

Required at Least Probable Cause of

Exigent or Emergency Circumstances for

Warrantless Home Entry, Even in

Emergencies.

Common-law expectations of privacy have long

guided this Court’s understanding of the Fourth

Amendment. At common law, officers had to obtain a

warrant to enter a person’s home in all but the most

extreme circumstances. And in those rare cases that

the common law excused officers who entered homes

without a warrant, it was because of imminent

threats, meaning readily observable proof of danger.

The Court should thus spell out for the lower courts

that, to the extent the Fourth Amendment permits an

emergency-aid exception to the warrant requirement

for home entry at all, this exception does not apply

absent probable cause to believe an emergency exists

at the time of entry. In the process, the Court should

clarify that the exception does not apply unless the

entry is reasonably expected to alleviate, rather than

worsen, the relevant emergency. Cf. Reed v. Town of

Gilbert, 576 U.S. 155, 171 (2015) (government burdens

on speech must “further[] a compelling interest”).

A. Founding-era common law sets the

expectations and standards for resolving

modern Fourth Amendment questions.

The Fourth Amendment protects “[t]he right of the

people to be secure in their persons, houses, papers,

and effects, against unreasonable searches and

seizures[.]” U.S. Const. amend. IV (emphasis added).

The Fourth Amendment’s default rule for a reasonable

search is that the search be pursuant to a “Warrant[]”

based “upon probable cause[.]” Ibid. Recognizing the

Amendment to be an “affirmance” of the common law

on these points, 2 the Court respects “historical

understandings ‘of what was deemed an unreasonable

search and seizure when [the Fourth Amendment] was

adopted.’” Carpenter v. United States, 585 U.S. 296,

305 (2018) (quoting Carroll v. United States, 267 U.S.

132, 149 (1925)).

In this regard, the common law furnishes two

“basic guideposts”: (1) the Fourth Amendment protects

the “privacies of life” from “arbitrary power,” ibid.

(quoting Boyd v. United States, 116 U.S. 616, 630

(1886)); and (2) the “central aim of the Framers was ‘to

place obstacles in the way of a too permeating police

surveillance,’” ibid. (quoting United States v. Di Re,

332 U.S. 581, 595 (1948)). This case implicates both

guideposts. As explained in Section II.A, at common

law, the “privacies of life” found their apex in the

home. Allowing the police to enter the home without a

warrant, consent, or even the existence of probable

cause that an emergency exists would remove a

meaningful historical obstacle to government

overreach.

2 3 Joseph Story, Commentaries on the Constitution of the United

States 748 (Boston, Hilliard, Gray & Co. 1833).

B. At common law, officers could enter a

home without a warrant only to arrest a

fleeing felon, if they witnessed an affray,

or upon observable proof they could

prevent imminent harm.

At common law, non-consensual warrantless entry

into the home was allowed only in the most extreme

circumstances, and never supported by less than

“probable suspicion.” While common-law officers, for

example, had a duty “to keep the peace,” 3 they still had

to get a warrant to enter a person’s home in all but the

rarest, most extreme cases. The mere possibility of a

threat to an individual based only on a third-party

report, with countervailing independent knowledge

that the threat is unlikely to materialize without

interference, would not have been such an extreme

case because it lacked sufficient proof of imminent

harm. Legal commentary and case law during and

after the founding period reflect this understanding.

1. English courts considered a man’s house his

“castle and fortress.” Semayne’s Case, 77 Eng. Rep.

194, 195 (K.B. 1604). As William Pitt famously put it:

“The poorest man may, in his cottage, bid defiance to

all the forces of the Crown. It may be frail; its roof may

shake; the wind may blow through it; the storm may

enter; the rain may enter; but the King of England

may not enter; all his force dares not cross the

threshold of the ruined tenement.” 4

3 2 Matthew Hale, Historia Placitorum Coronae (The History of

the Pleas of the Crown) 95 (Little Britain, E. Rider 1800).

4 Nelson B. Lasson, The History and Development of the Fourth

Amendment to the United States Constitution 49-50 (1937).

Outside certain rare “circumstances,” “the Crown

could not intrude on the sanctity of the home without

a warrant.” 5 The home was not to be “violated” unless

“absolute necessity” compelled such a violation to

“secure [a] public benefit.” 6 Otherwise, in “all cases

where the law” was “silent” and “express principles

d[id] not apply,” the “extreme violence” of warrantless

home entry was forbidden. 7 And even then, some

commentators maintained that it was never

permissible to so enter a home—even with a warrant.

Payton v. New York, 445 U.S. 573, 593-597 (1980). In

Lord Coke’s view, for instance, only an indictment

could “justify breaking down doors” to apprehend a

felon. 8

The Fourth Amendment, which Justice Story

recognized as “little more than the affirmance” of the

common law, 9 was meant by the Framers to continue

this tradition and prevent the “evil” of warrantless

“physical entry of the home.” Welsh v. Wisconsin, 466

U.S. 740, 748 (1984) (citation omitted).

Putting aside the stricter commentators and

taking the generally accepted founding-era approach,

the common law recognized only one scenario that

5 Laura K. Donohue, The Original Fourth Amendment, 83 U. Chi.

L. Rev. 1181, 1195-1196 (2016).

6 1 Joseph Chitty, A Practical Treatise on the Criminal Law 52

(London, A.J. Valpy 1816).

7 Ibid.

8 Edward Coke, The Fourth Part of the Institutes of the Laws of

England: Concerning the Jurisdiction of Courts 177 (Flesher

1644).

9 Story, supra note 2, at 748.

allowed warrantless home entry besides pursuit of a

felon or the raising of a hue-and-cry 10: an effort to stop

an “affray” to prevent imminent harm, and even then,

only upon strong evidence of such necessity. 11

The first American edition of Giles Jacobs’ law

dictionary describes an affray as “a skirmish or

fighting between two or more” in which “a stroke [is]

given, or offered, or a weapon drawn.” 12 If a peace

officer personally witnessed an affray, there was “no

doubt” that he could “do all such things” to end the

disturbance. 13 Consistent with this view, common-law

scholar Joseph Shaw noted that, “[w]hen an Affray is

in a House, the Constable, on his being refused

Entrance, may break it open to keep the Peace.” 14

Government authority to enter a house without a

warrant, however, was limited to cases in which the

10 The “hue and cry” exception was available only in a narrow

class of cases where the victim of a serious offense, often involving

“grievous[] and dangerous[] wound[s],” sought the assistance

from the Crown in apprehending a felon who had fled. See Br. of

Project for Privacy & Surveillance Accountability and Restore the

Fourth, Inc. as Amici Curiae Supporting Petitioner at 9-15, Lange

v. California, 594 U.S. 295 (2021) (No. 20-18) (exploring the

common-law exigent-circumstances exception and the hue and

cry), https://tinyurl.com/2wbuj9sk.

at 13 n.27 (citing 2 Matthew Hale, Historia Placitorum

Coronae (The History of the Pleas of the Crown) 95 (Phila., Robert

H. Small 1847)); 14 n.30 (citing Donohue, supra note 5, at 1226).

11 Id.

1 Giles Jacobs, The Law-Dictionary: Explaining the

Rise, Progress, and Present State, of the English Law 65 (Phila.,

I. Riley 1811).

12 Affray,

13 Ibid.

14 1 Joseph Shaw, The Practical Justice of the Peace 569 (London,

Henry Lintot, 4th ed. 1744).

officer heard or observed the affray and needed to

enter to prevent harm. As scholar Joseph Chitty

explained, an officer could “break open the doors” to

“suppress the tumult” if the affray is “within the view

or hearing of a constable” or upon hearing a “violent

cry of murder” within a house. 15

If an officer did not personally observe or hear an

affray in a home, entry required a warrant. William

Hawkins noted that “a Constable hath no Power to

arrest a Man for an Affray done out of his own View”

without a warrant, for “it is the proper Business of a

Constable to preserve the Peace, not to punish the

Breach of it.” 16 Matthew Hale agreed: If an affray was

past, “and no danger of death” remained, a constable

“could not arrest the parties without a warrant from

the justice of the peace[,]” much less enter a person’s

home. 17 Arrests for an affray based “on the

information and complaint from another” without the

constable’s presence were impermissible because, as

Hale concluded, “[i]t is difficult to find any instance

where a constable hath any greater power than a

private person over a breach of the peace out of his

view.” 18

Caution is required, however, when analogizing

home entry to quell affrays at common law to modern

emergencies. As Justice Thomas rightly recognizes,

15 1 Joseph Chitty, A Practical Treatise on the Criminal Law 56

(Springfield, G & C Merriam 1836) (emphasis added).

16 1 William Hawkins, A Treatise of the Pleas of the Crown 137

(London, Eliz. Nutt 1716).

17 Hale (1847), supra note 11, at 89.

18 Id. at 89-90 n.6.

“[a]ffrays were defined by their public nature and

effect.” United States v. Rahimi, 602 U.S. 680, 769

(2024) (Thomas, J., dissenting) (citing 4 William

Blackstone, Commentaries on the Laws of England

145 (1769)); accord Bruen, 597 U.S. at 120 (Breyer, J.,

dissenting) (quoting 1 William Hawkins, A Treatise of

the Pleas of the Crown 135 (London, Eliz. Nutt 1716)).

In other words, the common law justified warrantless

home entry to end an affray to protect residents and

restore public peace—interests that by their nature

presented an unusually strong need for police

intervention.

And even in the case of a “felony actually

committed, or a dangerous wounding whereby felony

is likely to ensue,” Blackstone still determined that

any warrantless entry of a home required “probable,”

not merely reasonable “suspicion.” 19

2. Following the careful path laid by common-law

scholars, this Court too has recognized “[t]he command

of the Fourth Amendment” to advance fundamental

“lesson[s]” about the “violent, obnoxious and

dangerous” character of “breaking an outer door.” Ker

v. California, 374 U.S. 23, 54 (1963) (plurality opinion)

(citing 1 Richard Burn, The Justice of the Peace, and

Parish Officer 275-276 (28th ed. 1837)). Carrying these

lessons forward, early American cases allowed

warrantless police entry into the home only in the most

urgent circumstances—and, even then, only upon a

showing of evidence equal to at least probable cause.

19 4 William Blackstone, Commentaries on the Laws of England

289 (1769) (emphasis added).

For example, in 1860, Massachusetts’ high court

explained that, at common law, the “authority of a

constable to break open doors and arrest without a

warrant” was “confined to cases where treason or

felony has been committed, or there is an affray or a

breach of the peace in his presence.” McLennon v.

Richardson, 81 Mass. 74, 77 (1860) (emphasis added)

(citations omitted). Peace breaches at common law

generally entailed violent crimes that involved

“assaulting, striking, or * * * fighting.” 20 Cases like

McLennon thus made clear that the only emergency

sufficient to justify warrantless home entry was a

violent event personally witnessed by the constable—

a standard even more demanding than probable cause.

This common-law rule did not change with time.

For example, in 1892, the New Jersey Court of Errors

and Appeals allowed an officer to enter a home without

a warrant to stop an affray short of a felony 21—but

20 Donohue,

supra note 5, at 1226 (quoting Saunders Welch,

Observations on the Office of Constable 6 (London, printed for A.

Millar 1754)); see also id. at 1226 n.262 (quoting William

Sheppard, The Offices and Duties of Constables 34 (London,

Richard Hodgkinsonne 1641) (“[A] breach of the peace was

understood as ‘not onely that fighting, which wee commonly call

the Breach of the Peace, but also that every Murder, Rape,

Manslaughter, and felonie whatsoever, and every Affraying, or

putting in feare of the Kings people.’” (spelling in original)).

21 “Felony,” as used at common law and in the treatises cited by

later American cases, was more than just a statutory distinction:

the term meant the most serious of crimes, making apprehension

for misdemeanors and prevention of affrays a better analogy for

emergency-aid searches. See, e.g., Gardner v. New Jersey, 26 A.

30, 32 (N.J. Sup. Ct. 1892) (“In the classification of criminal

offenses at common law, felony was a nomen generalis, which

comprised all offenses which occasioned a forfeiture of either

lands or goods or both, to which capital or other punishment was

only if the affray was committed in the officer’s

presence. The Court explained that, “[i]f the affray be

in a house, the constable may break open the doors to

preserve the peace; and if the affrayers fly to the

house, and he freshly follow, he may break open the

doors to take them without warrant. But he cannot,

without a warrant, arrest a man for an affray or breach

of the peace out of his view, unless it embrace a felony.”

Delafoile v. New Jersey, 24 A. 557, 558 (N.J. 1892)

(citations omitted). In this manner, American courts

reaffirmed that they would not permit warrantless

home entries absent an officer’s personal, direct

observation of an affray—closely analogous to a

requirement of probable cause.

3. In short, no common-law authority of which

Amici are aware approved the idea that emergencies

generally allow the police to enter a home without a

warrant—much less without probable cause—except

as necessary to apprehend a fleeing criminal or to

prevent an affray. By contrast, the emergency-aid

exception is a modern invention. And here, the

Supreme Court of Montana has extended this

invention to its logical limit, holding that the exception

allows warrantless entry even when a court would

probably not have issued a warrant had the police

sought one.

super-added, according to the degree of guilt.” (citations

omitted)), aff’d, 30 A. 429 (N.J. 1893) (per curiam); Felony, Black’s

Law Dictionary 483 (1st ed. 1891) (“In American Law. The Term

has no very definite or precise meaning * * * The statutes or codes

of several of the states define felony as any public offense on

conviction of which the offender is liable to be sentenced to death

or to imprisonment in a penitentiary or state prison.”).

Illustrating the newness of this entire doctrine,

this Court first articulated the emergency-aid

exception in 1978, 22 and state court cases do not seem

to date back much further. 23 Careful examination of

the Court’s seminal cases articulating the exception,

moreover, shows just how narrow this Court

considered the exception, which each reflecting

circumstances like the “affray” of English common law.

In Michigan v. Fisher, for example, the police

entered a home because they “could see violent

behavior inside.” 558 U.S. 45, 48 (2009). Later, in

Brigham City v. Stuart, police officers watched as a

young man broke free and struck an officer. 547 U.S.

398, 406 (2006). Like founding-era cases that justified

warrantless entry following an affray, the Court’s

emergency-aid cases involved the police personally

observing violent behavior.

Most relevant here, at the very least, this

exception requires an “objectively reasonable basis to

believe that there is a current, ongoing crisis for which

it is reasonable to act now.” Caniglia v. Strom, 593

U.S. 194, 206 (2021) (Kavanaugh, J., concurring)

(emphasis added). 24 Here, by contrast, Case never

22 Mincey v. Arizona, 437 U.S. 385, 392 n.6 (1978) (citing Melinda

Roberts, Note, The Emergency Doctrine, Civil Search and Seizure,

and the Fourth Amendment, 43 Ford. L. Rev. 571, 584 n.102

(1975)).

23 See Roberts, supra note 22, at 585 n.106 (collecting cases).

24 The “objectively reasonable basis” is not a level of suspicion.

Rather, it is language from Brigham City, where this Court

rejected the argument that the emergency-aid exception requires

analysis of the subjective motive of officers. Brigham City v.

Stuart, 547 U.S. 398, 404 (2006).

requested police aid; the officers responded to a report

from Case’s ex-girlfriend. App.3a. Besides an empty

holster and a notepad, the officers lacked any evidence

of a potential emergency when they arrived at the

home. App.4a. Any emergency was also so attenuated

that the police saw fit to wait at least forty minutes

before entering, belying the argument that there was

an imminent threat to Case’s life. App.5a. Worse,

police entered even though they believed that Case

was likely waiting for them and would not harm

himself if they stayed outside. App.29a. Rather than

resolving the threat, then, the police contributed to it.

Applying the emergency-aid exception here would thus

dishonor the founding era’s protection of the home—

given that the basis for the search falls far short of the

absolute floor the Fourth Amendment sets.

This is no surprise either: The decision below

explicitly models itself on Fourth Amendment rules for

searches of vehicles and public places—not homes.

Montana “first recognized the doctrine” applied below

in Montana v. Lovegren, 51 P.3d 471, 475 (Mont. 2002).

Est. of Frazier v. Miller, 484 P.3d 912, 918 (Mont.

2021). Lovegren devoted multiple pages to explaining

that the low bar for justifying police stops applied even

to home entries if there were some colorable

suggestion that an emergency was ongoing. 51 P.3d at

473-476 (citing, inter alia, Terry v. Ohio, 392 U.S. 1

(1968)).

The decision below thus affirms the warrantless

police entry of Case’s home through language that is

nearly identical to the Fourth Amendment standard

for safety frisks and traffic stops. Compare App.12a15a (requiring “objective, specific and articulable facts

from which an experienced officer would suspect that

a citizen is in need of help or is in peril” (citation

omitted)), with Michigan v. Long, 463 U.S. 1032, 1049

(1983) (requiring only “specific and articulable facts”

to search an automobile trunk for weapons (citation

omitted)); and Terry, 392 U.S. at 7, 21 (requiring

“specific and articulable facts” for a weapons frisk).

This is a problem. By modeling its emergency-aid

exception on the Terry standard and adopting the

same language that this Court has used when

discussing the standard applied to searches of areas

less protected than the home, the decision below

ignored what this Court has called the “unmistakable

distinction between vehicles and homes.” Caniglia,

593 U.S. at 199. Such a dangerous flouting of this

Court’s precedent should be rejected. It turns the

Fourth Amendment’s warrant requirement into a

warrant suggestion and allows police to enter a

person’s home in circumstances when no warrant

would issue. For this reason, this Court should put a

definitive end to the misguided view that emergencies

allow the police to treat homes as something other

than homes by holding that any emergency-aid

exception requires probable cause of an ongoing

emergency.

II. If the Evidentiary Threshold for the

Emergency-Aid Exception Were Lowered, It

Could Easily Be Used to Justify Extensive

Warrantless Electronic Surveillance.

While the common law’s limited application of, and

higher evidentiary burden for, an emergency-aid

exception is sufficient reason to reverse here, it is not

the only reason. When it comes to the Fourth

Amendment—which also protects electronic devices,

accounts, and communications—the home is the “first

among equals.” Florida v. Jardines, 569 U.S. 1, 6

(2013). Thus, if the government may enter a home

without a warrant based on articulable suspicion of an

emergency—a standard far short of probable cause—

digital information will be next. The insidious

branding writes itself: “Big Brother” may be

“watching,” but it’s for your own good! 25 Guarding

against such surveillance is another powerful reason

for the Court to reverse the decision below.

A. Electronic surveillance raises the same

Fourth Amendment concerns as

warrantless home entry.

Electronic devices today hold many of the

“privacies of life” that were once found only in the

home. Riley v. California, 573 U.S. 373, 403 (2014)

(citation omitted). Indeed, as Justice Alito has

explained, “because of the role that these devices have

come to play in contemporary life, searching their

contents implicates very sensitive privacy interests[.]”

Id. at 408 (Alito, J., concurring in part and in the

judgment). Indeed, “[m]odern cell phones * * *

25 George Orwell, 1984, at 26 (1949).

implicate privacy concerns far beyond those implicated

by the search of a cigarette pack, a wallet, or a purse.”

Id. at 393 (majority opinion).

The Court has thus correctly emphasized that “a

cell phone search [today] would typically expose to the

government far more [personal information] than the

most exhaustive search of a house[.]” Id. at 396

(emphasis in original). Indeed, “[a] phone not only

contains in digital form many sensitive records

previously found in the home; it also contains a broad

array of private information never found in a home in

any form[.]” Id. at 396-397. Even the choice of

applications on a phone can reveal significant private

details. There are “apps for alcohol, drug, and

gambling addictions; apps for sharing prayer requests;

apps for tracking pregnancy symptoms; apps for

planning your budget; * * * [and] apps for improving

your romantic life.” Id. at 396. And many Americans

use their phones for even the most sensitive of

activities imaginable: mental-health counseling 26 or

sexually explicit communications with their intimate

partners. 27 Phones also track their owner’s location,

creating data that shows not only where a person

26 Amy Novotney, A growing wave of online therapy, 48 Monitor

on Psych. 48 (Feb. 2017), https://tinyurl.com/mrpmu68j.

27 Elizabeth Kinsey Hawley, Sexting Felonies: A Major Problem

for Minors, Communicating Psych. Sci. (Aug. 2020),

https://tinyurl.com/4aszmauh; Sasha Harris-Lovett, In survey,

88% of U.S. adults said they had sexted and 96% of them endorsed

it, L.A. Times (Aug. 8, 2015), https://tinyurl.com/3cm945sk.

worships, banks, and studies, but also where and with

whom a person spends her free time. 28

Several “interrelated consequences for privacy”

follow from the ubiquity of electronic devices. Riley,

573 U.S. at 394. Most important, the many “distinct

types of information” on phones may “reveal much

more in combination than any isolated record” and

may “date back to the purchase of the phone[.]” Ibid.

There is also a “pervasiveness” that “characterizes cell

phones but not physical records. Prior to the digital

age, people did not typically carry a [vast] cache of

sensitive personal information with them as they went

about their day.” Id. at 395.

But today, phones and similar devices—with all

their sensitive information—are everywhere. As of

mid-2024, “[t]he vast majority of Americans—98%—

now own a cellphone of some kind,” with 91% of

Americans owning a smartphone. 29 Americans also

own a range of other information devices. Nearly 81%

of U.S. adults now own desktop or laptop computers

and 64% own tablet computers. 30 And Americans are

increasingly online, with 96% of Americans using the

28 Novotney, supra note 26 (“[S]ome [counseling] apps do report

that they use a member’s IP address to determine their exact

location and send police if a therapist is concerned about a

member’s safety[.]”).

Fact Sheet, Pew

https://tinyurl.com/3fw242ry.

29 Mobile

30 Press

Rsch.

Ctr.

(Nov.

13,

2024),

Release, U.S. Census Bureau, No. CB24-TPS.61,

Computer and Internet Use in the United States: 2021 (June 18,

2024), https://tinyurl.com/bdfkskay.

internet, likely with some regularity 31—a point that

this Court appreciated in considering ongoing changes

in technology last term. See, e.g., Free Speech Coal.,

Inc. v. Paxton, 145 S. Ct. 2291, 2314 (2025) (noting “in

2024, 95 percent of American teens had access to a

smartphone, allowing many to access the internet at

almost any time and place.”). Since most Americans

are connected to an electronic device connected to the

internet, unlimited police surveillance of electronic

devices poses an existential risk to the very idea of

privacy.

Nor is the information obtainable on a device

limited to the device itself given the rise of remote data

collection and cloud storage. See Riley, 573 U.S. at 397.

Cloud-based storage—including those found in remote

hard drives, social-media accounts, and email—all

contain as much or even more private information as

any given device, making this storage frequent targets

of government surveillance. See, e.g., Heidi Grp., Inc.

v. Texas Health & Hum. Servs. Comm’n, 138 F.4th 920,

935 (5th Cir. 2025) (remote storage service Dropbox);

United States v. Zelaya-Veliz, 94 F.4th 321, 333-334

(4th Cir. 2024) (private social media), cert. denied

mem., 145 S. Ct. 571 (2024); United States v. Warshak,

631 F.3d 266, 287-288 (6th Cir. 2010) (private email

account).

Because of the ubiquity of electronic devices and

the vast amount of private, personal information they

contain, searching a person’s electronics or accounts

today is just as intrusive (if not more so) than

31 Internet, Broadband Fact Sheet, Pew Rsch. Ctr. (Nov. 13, 2024),

https://tinyurl.com/7zcautch.

searching the same person’s home. And it raises the

same privacy concerns. Vitiating the Fourth

Amendment’s protections against warrantless entry of

homes thus virtually guarantees a downstream

dilution of Fourth Amendment protections against

warrantless searches of electronic devices and

accounts.

B. Absent a fixed rule of probable cause,

warrantless electronic surveillance

could become routine and severely

compromise Americans’ privacy.

Given the historic sanctity and privacy of homes,

any lowering of the government’s burden when it

comes to home entry risks the same for every other

repository of private information. It would take little

effort for the government to use (or abuse) purported

concern for a person’s safety to justify tracking the

person’s online activity, reading the person’s emails,

and searching the person’s electronic devices.

1. For example, lowering the bar for warrantless

emergency-aid searches would allow warrantless

surveillance even if “there is no claim of criminal

liability” and the search is “divorced from the

detection, investigation, or acquisition of evidence

relating to the violation of a criminal statute.” Cady v.

Dombrowski, 413 U.S. 433, 441 (1973). Indeed, this

Court has suggested that the related exigentcircumstances doctrine applies to electronic devices.

See Riley, 573 U.S. at 402. But if the exigentcircumstances doctrine were coupled with Montana’s

low bar for suspecting an emergency, digital privacy

would all but vanish. After all, electronic devices stand

to reveal a host of caretaking- or emergency-relevant

information about a person’s mental, emotional, and

physical well-being. Warrantless surveillance of these

devices then becomes simply a matter of articulable

suspicion of an “emergency,” which the government

may easily manifest. And with that, nothing remains

of privacy for many or even most Americans.

And, while the physical dimensions of home

searches carry practical limits to a search’s scope, the

government can perform electronic searches remotely

and in gross. See Fed. R. Crim. P. 41(b)(6) (judges may

“issue a warrant to use remote access to search

electronic storage media and to seize or copy

electronically stored information”). Sophisticated

automated techniques and algorithms (including

artificial intelligence), in turn, allow the government

to scan massive databases for targets with the click of

a button that would have taken countless hours in

years past. E.g., United States v. Smith, 110 F.4th 817,

837-838 (5th Cir. 2024) (discussing Google’s scan of

over half-a-billion accounts to find matches for a

geofence warrant), petition for cert. docketed, No. 247237 (U.S. May 19, 2025).

In practice, that means that a “government agent

in Virginia” may “hack into a website located on a

server in Kansas, or even Russia.” 32 The same agent

may also remotely “verify that the same computer that

had been connected at [one] IP address” is now

connected at another. United States v. Heckenkamp,

32 Jeremy

A. Moseley, The Fourth Amendment and Remote

Searches: Balancing the Protection of “The People” with the

Remote Investigation of Internet Crimes, 19 Notre Dame J.L.

Ethics & Pub. Pol’y 355, 356 (2005).

482 F.3d 1142, 1148 (9th Cir. 2007). And once the

government has access, it may easily access

everything stored on a given device.

2. Worse still, the government can acquire such

access through garden-variety, remote hacking, which

“has the potential to be far more intrusive than any

other surveillance technique[.]” 33 Through hacking,

the government can “conduct novel forms of real-time

surveillance, by covertly turning on a [target] device’s

microphone, camera, or GPS-based locator technology,

or by capturing continuous screenshots or seeing

anything input into and output from the device.” 34

The government is fully aware of that potential

and has acted on it. Following the San Bernardino

shooting, when Apple declined to obey a warrant

requiring it to introduce a backdoor into its iOS

software, the FBI paid “professional hackers” to

discover a “previously unknown software flaw.” 35 And

once hackers discover software vulnerabilities, they

“do not disclose the flaws to the companies * * * as the

exploit’s value depends on the software remaining

vulnerable.” 36 While the government has a “strong

bias” in favor of disclosing such vulnerabilities once it

Hacking, Privacy Int’l,

mr2xnyb4 (last visited Aug. 1, 2025).

33 Government

https://tinyurl.com/

34 Ibid.

35 Ellen Nakashima, FBI paid professional hackers one-time fee to

crack San Bernardino iPhone, Wash. Post (Apr. 12, 2016),

https://tinyurl.com/3zrzew6u.

36 Ibid.

learns of them, disclosure isn’t required. 37 The hacker

that helped the FBI in the San Bernardino case, for

example, had sole legal ownership of the method that

he used, making it unlikely that the government will

disclose the technique to Apple.

3. And—if the government can so hack devices—

articulable suspicion of an emergency presents

limitless opportunities for warrantless electronic

surveillance. Whether to learn a “suspect’s identity,”

to “obtain a suspect’s [past] communications,” or to

“intercept future conversations,” government hacking

“will only become more commonplace.” 38

Imagine, for example, that the police suspected

that a person posed a risk to himself or others. Under

the emergency-aid exception recognized below—an

exception lacking any required showing of probable

cause—the police may conduct a warrantless search of

the person’s phone for purposes of risk assessment.

The police may then browse the person’s search

history, text messages, call logs, and photos—all in the

name of preventing an emergency. During that search,

the police will almost certainly encounter deeply

personal private information. They might also stumble

across evidence of unrelated, non-exigent illegal

activity.

The police will then likely seize and use that

evidence against the person. After all, another

“exception to the warrant requirement is the seizure of

37 Andrew Crocker, FAQ: Apple, the FBI, and Zero Days, Elec.

Frontier Found. (Apr. 14, 2016), https://tinyurl.com/2uj2waum.

38 Jonathan Mayer, Government Hacking, 127 Yale L.J. 570, 577-

578 (2017).

evidence in ‘plain view.’” Cady, 413 U.S. at 452

(Brennan, J., dissenting). This doctrine applies when

an officer with “prior justification for an intrusion”—

e.g., to respond to an emergency—“inadvertently

[comes] across a piece of evidence incriminating” a

person. Coolidge v. New Hampshire, 403 U.S. 443, 466

(1971). If the police do not violate the Fourth

Amendment when they search a home or a phone

while acting under a valid warrant exception, then

anything incriminating they see in that capacity may

be used against a person in a criminal prosecution.

See, e.g., Kentucky v. King, 563 U.S. 452, 462-463

(2011) (“law enforcement officers may seize evidence

in plain view, provided that they have not violated the

Fourth Amendment in arriving at the spot from which

the observation of the [seized] evidence is made”).

Seemingly benevolent searches would then become

an engine for criminal prosecutions even though no

warrant was ever obtained, and no probable cause ever

existed. The emergency-aid exception would thus

reduce to a license for the government to discover

criminal activity that—in all other circumstances—

would only have been discoverable through a warrant

supported by probable cause. As Justice Robert

Jackson famously put it, the government is bound to

“push to the limit” any “privilege of search and seizure

without warrant” that the Court “sustain[s].” Brinegar

v. United States, 338 U.S. 160, 182 (1949) (Jackson, J.,

dissenting). 39 Preservation of the Fourth Amendment

then depends on this Court’s reaffirming standards

39 Because Justice Jackson had served as Solicitor General before

writing his Brinegar dissent, one wonders if he was speaking from

personal experience.

like probable cause that the Framers recognized

protect the privacies of life against government abuse.

CONCLUSION

The common law of the founding era recognized

that circumstances allowing the police to enter a home

without a warrant should be very few and even farther

between. Failing to recognize this, the court below

turned a narrow Fourth Amendment exception for

emergencies into a rule that risks swallowing the

Fourth Amendment whole. Rejection of this approach

will ensure that the “privacies of life” embodied by

every person’s home—and by their electronic devices

too—remain protected by the Fourth Amendment.

Respectfully submitted,