United States of America v. LUKE NOEL WILSON

San Francisco - Criminal defense lawyer represented defendant

with a possession and distribution of child pornography charge.

We once again consider the application of the Fourth

Amendment's warrant requirement to new forms of

communication technology. See, e.g., United States v. Cano,

934 F.3d 1002 (9th Cir. 2019); cf. Carpenter v. United

States, 138 S. Ct. 2206 (2018). "When confronting [such]

concerns wrought by digital technology, th[e] [Supreme]

Court [and this court] ha[ve] been careful not to uncritically

extend existing precedents.” Id. at 2222. Our question this

time concerns the private search exception to the Fourth

Amendment—specifically, the intersection between

electronic communications providers' control over material

on their own servers and the Fourth Amendment's restriction

of warrantless searches and seizures, which limits only

governmental action. See Burdeau v. McDowell, 256 U.S.

465 (1921); Walter v. United States, 447 U.S. 649 (1980);

United States v. Jacobsen, 466 U.S. 109 (1984).

The events giving rise to Luke Wilson's conviction and

this appeal were triggered when Google, as required by

federal law, reported to the National Center for Missing and

Exploited Children (NCMEC) that Wilson had uploaded

four images of apparent child pornography to his email

account as email attachments. No one at Google had opened

or viewed Wilson's email attachments; its report was based

on an automated assessment that the images Wilson

uploaded were the same as images other Google employees

had earlier viewed and classified as child pornography.

Someone at NCMEC then, also without opening or viewing

them, sent Wilson's email attachments to the San Diego

Internet Crimes Against Children Task Force (ICAC), where

an officer ultimately viewed the email attachments without

a warrant. The officer then applied for warrants to search

6 UNITED STATES V. WILSON

both Wilson's email account and Wilson's home, describing

the attachments in detail in the application.

Our question is whether the government's warrantless

search of Wilson's email attachments was justified by the

private search exception to the Fourth Amendment. See

Walter, 447 U.S. at 655–56; Jacobsen, 466 U.S. at 113–14.

For the reasons that follow, we hold that it was not. We

therefore reverse the district court's denial of Wilson's

motion to suppress and vacate Wilson's conviction.

I. Background

A. Google's Identification of Apparent Child

Pornography

Electronic communication service providers are not

required "affirmatively [to] search, screen, or scan” for

apparent violations on their platforms of federal child

pornography laws. 18 U.S.C. §§ 2258A(f), 2258E. But "[i]n

order to reduce . . . and . . . prevent the online sexual

exploitation of children,” such providers, including Google,

are directed, "as soon as reasonably possible after obtaining

actual knowledge” of "any facts or circumstances from

which there is an apparent violation of . . . child pornography

[statutes],” to "mak[e] a report of such facts or

circumstances” to NCMEC. 18 U.S.C. § 2258A(a).1

NCMEC then forwards what is known as a CyberTip to the

1 "A provider that knowingly and willfully failed to make a report

required . . . shall be fined.” 18 U.S.C. § 2258A(e). Further, in the case

of "intentional, reckless, or other misconduct,” there may be "a civil

claim or criminal charge against a provider . . . arising from the

performance of the reporting or preservation responsibilities.” Id. at

§§ 2258B(a), (b).

UNITED STATES V. WILSON 7

appropriate law enforcement agency for possible

investigation. Id. at §§ 2258A(a)(1)(B)(ii), (c).

According to a two-page declaration from a senior

manager at Google, the company "independently and

voluntarily take[s] steps to monitor and safeguard [its]

platform,” including using a "proprietary hashing

technology” to identify apparent child pornography.2

As described in the record—vaguely, and with the gaps

noted—the process works as follows:

First, a team of Google employees are "trained by

counsel on the federal statutory definition of child

pornography and how to recognize it.” Neither the training

materials themselves nor a description of their contents

appear in or are attached to the Google manager's

declaration.

Second, these employees "visually confirm[]” an image

"to be apparent child pornography.” According to an

industry classification standard created by various electronic

service providers, there are four industry categorizations:

"A1” for a sex act involving a prepubescent minor; "A2” for

a lascivious exhibition involving a prepubescent minor;

"B1” for a sex act involving a pubescent minor; and "B2”

for a lascivious exhibition involving a pubescent minor.

Third, "[e]ach offending image” judged to be "apparent

child pornography as defined in 18 USC § 2256” is given a

hash value, which is "added to [the] repository of hashes.”

2 "A hash value is (usually) a short string of characters generated

from a much larger string of data (say, an electronic image) using an

algorithm.” United States v. Ackerman, 831 F.3d 1292, 1294 (10th Cir.

2016).

8 UNITED STATES V. WILSON

As far as the record shows, Google "stores only the hash

values” of images identified as apparent child pornography,

not the actual images. The government does not represent

otherwise.

Finally, Google "[c]ompare[s] these hashes to hashes of

content uploaded to [their] services.” The exact manner in

which hash values are assigned to either the original

photographs or the ones deemed to replicate them is not

described in the Google manager's declaration or anywhere

else in the record.

B. Government Search

On June 4, 2015, Google, using its propriety technology,

"became aware” that Wilson had attached to emails in his

email account—which may or may not have been sent—four

files that included apparent child pornography. United States

v. Wilson, No. 3:15-cr-02838-GPC, 2017 WL 2733879, at

*3 (S.D. Cal. June 26, 2017). In compliance with its

reporting obligations, Google automatically generated and

sent an electronic CyberTipline report to NCMEC. The

CyberTipline report included Wilson's four email

attachments. According to the Google manager's

declaration, "a Google employee did not view the images . . .

concurrently to submitting the report to NCMEC.” The

CyberTipline report did specify that Google had classified

each of Wilson's four email attachments as "A1” under an

industry classification standard for "content [which]

contain[s] a depiction of a prepubescent minor engaged in a

sexual act.”

Google's report included Wilson's email address,

secondary email address, and IP addresses. NCMEC

supplemented Google's report with geolocation information

UNITED STATES V. WILSON 9

associated with Wilson's IP addresses, but did "not open[]

or view[] any uploaded files submitted with this report.”

NCMEC then forwarded the CyberTip to the San Diego

Internet Crimes Against Children Task Force ("ICAC”).

Agent Thompson, a member of the San Diego ICAC,

received the report. He followed San Diego ICAC

procedure, which at the time called for inspecting the images

without a warrant whether or not a Google employee had

reviewed them.3

After Agent Thompson looked at Wilson's four email

attachments, he applied for a search warrant of Wilson's

email account. His affidavit asserted that probable cause for

the warrant was based on two facts: first, that "Google

became aware of four (4) image files depicting suspected

child pornography;” and second, that he had "reviewed the

four (4) images reported by Google to NCMEC and

determined they depict child pornography.” In support of his

own child pornography assessment, he included in the

warrant application detailed "descriptions of each of these

images.” The affidavit did not include the fact that Google

had originally classified the images as "A1” or provide any

detail about how Google had either classified or later

automatically identified Wilson's images as apparent child

pornography.

On the basis of the application and affidavit submitted

by Agent Thompson, a magistrate judge issued a search

3 Agent Thompson testified that San Diego ICAC, which includes

both local, county, regional, and federal agencies, now obtains a search

warrant before opening a CyberTip when the provider has not viewed

the images. It is not clear from the record whether other ICAC task forces

across the country have adopted the same policy.

10 UNITED STATES V. WILSON

warrant for Wilson's email account. When Agent Thompson

executed the warrant, he discovered numerous email

exchanges in which Wilson received and sent images and

video files of alleged child pornography and in which

Wilson offered to pay for the creation of child pornography.

Agent Thompson then obtained a search warrant for

Wilson's residence. On executing the warrant, law

enforcement officers found and seized several electronic

devices that contained evidence of child pornography. One

officer observed a backpack being tossed over Wilson's

balcony at the time officers were knocking on Wilson's door

and announcing their presence. Wilson's checkbook and a

thumb drive containing thousands of images of child

pornography—including the four images reported by

Google—were found in the backpack.

C. Motion to Suppress

Wilson filed a motion to suppress all evidence seized

from his email account and residence, arguing that Agent

Thompson's review of his email attachments without a

warrant was impermissible under the Fourth Amendment.

Relying principally on Jacobsen, 466 U.S. 109, and United

States v. Tosti, 733 F.3d 816 (9th Cir. 2013), the government

maintained in response that Agent Thompson's review of the

four images did not exceed the scope of Google's private

search and so, under the private search doctrine as

enunciated in Jacobsen and Tosti, was valid without a

warrant.

The district court agreed. The court denied Wilson's

motion to suppress on the ground that the government's

warrantless search did not exceed the scope of the antecedent

private search and so did not require a warrant. The district

court also concluded that "if [Agent] Thompson's

UNITED STATES V. WILSON 11

warrantless viewing of the four images constituted an illegal

search, neither excising the tainted evidence from the

affidavit nor the good faith exception would prevent

operation of the exclusionary rule.”4 Wilson, 2017 WL

2733879, at *12–13.

After waiving his right to a jury trial, Wilson was

convicted of possession and distribution of child

pornography5 and sentenced to 11 years of incarceration and

4 The government does not contest these contingent rulings.

5 While this appeal was pending, the California Court of Appeal held

that "the government's warrantless search of Wilson's four images was

permissible under the private search doctrine.” People v. Wilson, 56 Cal.

App. 5th 128, 147 (2020), as modified on denial of reh'g (Nov. 6, 2020),

review denied (Jan. 20, 2021). We have not squarely addressed the

preclusive effect of the denial of a suppression motion in an earlier statecourt proceeding. Other circuits, however, have held that "the

government may not collaterally estop a criminal defendant from

relitigating an issue against the defendant in a different court in a prior

proceeding.” United States v. Harnage, 976 F.2d 633, 636 (11th Cir.

1992); accord United States v. Pelullo, 14 F.3d 881, 896 (3d Cir. 1994);

United States v. Gallardo-Mendez, 150 F.3d 1240, 1244 (10th Cir.

1998). Citing those cases, we came to the similar conclusion that, in

criminal trials, the government "may not use collateral estoppel to

establish, as a matter of law, an element of an offense or to conclusively

rebut an affirmative defense on which the Government bears the burden

of proof beyond a reasonable doubt.” United States v. Smith-Baltiher,

424 F.3d 913, 920 (9th Cir. 2005) (quoting United States v. Arnett,

353 F.3d 765, 766 (9th Cir. 2003) (en banc) (per curiam)).

We need not definitively resolve the preclusion question as it relates

to a motion to suppress, here, as the government has not asserted

collateral estoppel, so the argument is waived. Harbeson v. Parke Davis,

Inc., 746 F.2d 517, 520 (9th Cir. 1984) ("The United States was unaware

that Mr. Wilson had raised the same issue in his state appeal until the

letter filed in this case by [defense counsel] on October 16, 2020.”).

12 UNITED STATES V. WILSON

10 years of supervised release for each count, to run

concurrently.6

II. Discussion

The government does not dispute for purposes of this

case Wilson's assertion that Agent Thompson's review of

his email attachments was a search within the meaning of the

Fourth Amendment. We proceed on that assumption as

well—that is, we assume that Wilson had a subjective

expectation of privacy in his email attachments that society

is prepared to recognize as reasonable, see Kyllo v. United

States, 533 U.S. 27, 33 (2001) (citing Katz v. United States,

389 U.S. 347, 361 (1967) (Harlan, J., concurring)); see also

United States v. Miller, 982 F.3d 412, 427 (6th Cir. 2020)

(taking the same approach); cf. United States v. Ackerman,

831 F.3d 1292, 1308 (10th Cir. 2016) (holding that when the

government views email attachments it is a "search” for

Fourth Amendment purposes under both an expectation-ofprivacy and a trespass-to-chattels theory).7 Our question,

then, is whether Agent Thompson was permitted to look at

Wilson's email attachments under the private search

6 Wilson maintains that the district court did not obtain a valid

waiver of his right to a jury trial, as required by Fed. R. Crim. P. 23(a).

Because we vacate Wilson's conviction and reverse the district court's

denial of Wilson's motion to suppress, we do not reach this issue.

7 Because we hold that the government's warrantless search violated

Wilson's privacy-based Fourth Amendment rights, we do not consider

Wilson's alternative argument that the government's search violated his

property-based Fourth Amendment rights. See Carpenter v. United

States, 138 S. Ct. 2206, 2269 (2018) (Gorsuch, J. dissenting) ("[F]ew

doubt that e-mail should be treated much like the traditional mail it has

largely supplanted—as a bailment in which the owner retains a vital and

protected legal interest.”).

UNITED STATES V. WILSON 13

exception, such that the Fourth Amendment did not require

him to procure a warrant.

We review the district court's denial of Wilson's motion

to suppress de novo and the district court's underlying

factual findings for clear error. See United States v. Camou,

773 F.3d 932, 937 (9th Cir. 2014); see also United States v.

Mulder, 808 F.2d 1346, 1348 (9th Cir. 1987).

A. Private Search Exception

As the Fourth Amendment protects individuals from

government actors, not private ones, see Burdeau v.

McDowell, 256 U.S. 465 (1921), a private party may conduct

a search that would be unconstitutional if conducted by the

government. The private search doctrine concerns

circumstances in which a private party's intrusions would

have constituted a search had the government conducted it

and the material discovered by the private party then comes

into the government's possession. Invoking the precept that

when private parties provide evidence to the government "on

[their] own accord[,] ... it [i]s not incumbent on the police

to . . . avert their eyes,” Coolidge v. New Hampshire,

403 U.S. 443, 489 (1971), the Supreme Court formalized the

private search doctrine in a pair of decisions about four

decades ago: Walter v. United States, 447 U.S. 649 (1980),

which produced no majority decision, and United States v.

Jacobsen, 466 U.S. 109 (1984), which did.

1. Doctrinal Foundations

Beginning from the initial articulation of the private

search doctrine, the extent to which it excuses the

government from compliance with the warrant requirement

of the Fourth Amendment has been the subject of concern.

The exception has, for example, been described as

14 UNITED STATES V. WILSON

"unsettling” for its potential reach. 1 Wayne R. LaFave,

Search and Seizure: A Treatise on the Fourth Amendment

§1.8(b) (6th ed. 2020); see also Jacobsen, 466 U.S. at 129–

34 (White, J., concurring in part and concurring in

judgment). On examination, however, the history of the

exception confirms that it is, in truth, a narrow doctrine with

limited applications.

Beginning with Burdeau, the Supreme Court has

distinguished between government agents and private

parties for purposes of the Fourth Amendment. Burdeau

considered whether the Fourth Amendment restricts the

government's ability to use papers incriminating an

individual when those papers were volunteered to the

government by a private party who had stolen them. Burdeau

disregarded the private theft, noting that although "[t]he

Fourth Amendment gives protection against unlawful

searches and seizures, . . . its protection applies to

governmental action.” 256 U.S. at 475.

Coolidge, decided 50 years after Burdeau, addressed

whether a private party who provides the government with

another person's contraband or evidentiary material can be

considered an agent of the government for purposes of the

Fourth Amendment. In that case, local police officers arrived

at a suspect's home, questioned his wife about his

involvement in a murder, and obtained from his wife a rifle

and articles of clothing belonging to the suspect. Coolidge,

403 U.S. at 446, 486. The opinion does not explain whether

the suspect's wife had proper possession of the items. The

Court stated only that, had the suspect's wife, "wholly on her

own initiative, sought out her husband's guns and clothing

and then taken them to the police station to be used as

evidence against him, there can be no doubt under [Burdeau]

that the articles would later have been admissible in

UNITED STATES V. WILSON 15

evidence.” Id. at 487. The relevant inquiry, according to the

Court, was whether the suspect's wife, "in light of all the

circumstances of the case, must be regarded as having acted

as an instrument or agent of the state when she produced her

husband's belongings.” Id. (internal quotation marks

omitted). As the record showed that the suspect's wife had

shared the suspect's guns and clothes with the local police

"of her own accord,” Coolidge held that "it was not

incumbent on the police to stop her or avert their eyes” when

offered the critical evidence. Id. at 489.

2. Doctrinal Scope

Following Burdeau and Coolidge, both Walter and

Jacobsen considered a warrantless government search after

a private party "freely made available” certain information

for the government's inspection. Jacobsen, 466 U.S. at 119–

20 (citing Coolidge, 403 U.S. at 487–90). Together, the cases

determined that an antecedent private search excuses the

government from obtaining a warrant to repeat the search but

only when the government search does not exceed the scope

of the private one. That is, "[t]he additional invasions of

respondents' privacy by the government agent must be tested

by the degree to which they exceeded the scope of the private

search.” Id. at 115.

In Walter, a package of obscene films was mistakenly

delivered to the wrong recipient. 447 U.S. at 651. The

recipient opened the external packaging and examined the

boxes containing individual films. Id. at 651–52. Each box

displayed "suggestive drawings” on one side and "explicit

descriptions of the contents” of the film on the other. Id.

at 652. After reading these descriptions, and "attempt[ing]

without success to view portions of the film by holding it up

to the light,” the recipient notified the FBI about the

mistaken delivery. Id. The FBI then seized the boxes and

16 UNITED STATES V. WILSON

screened one of the films without first obtaining a warrant.

Id.

Walter did not result in a majority opinion, but a majority

of the justices concluded that there had been a violation of

the Fourth Amendment, and a different majority of justices

agreed on the standard to be applied.

Justice Stevens, joined by Justice Stewart, announced the

judgment of the Court. Their opinion concluded that the

government search exceeded the scope of the antecedent

actions by the private individuals in two respects. First, the

government agents had screened the film for the purpose of

learning information necessary to determine that a crime had

been committed:

It is perfectly obvious that the agents' reason

for viewing the films was to determine

whether their owner was guilty of a federal

offense. To be sure, the labels on the film

boxes gave them probable cause to believe

that the films were obscene and that their

shipment in interstate commerce had

offended the federal criminal code. . . . [But]

a search of the contents of the films . . . was

necessary in order to obtain the evidence

which was to be used at trial.

Id. at 654. Second, the government agents had gone beyond

the physical bounds of the private search, because "the

private party had not actually viewed the films.” Id. at 657.

"The private search [thus] merely frustrated [the]

expectation [of privacy] in part,” not in full. Id. at 659. "It

UNITED STATES V. WILSON 17

did not simply strip the remaining unfrustrated portion of

that expectation of all Fourth Amendment protection.” Id. 8

The four justices in dissent would have concluded that

there was no Fourth Amendment violation. The dissenters

disputed not the basic approach of Justice Stevens' opinion

but its application to the facts of the case. Specifically, the

dissent stressed that "[t]he containers. . . clearly revealed the

nature of their contents,” such that the private employees "so

fully ascertained the nature of the films . . . [that] the FBI's

subsequent viewing of the movies . . . was not an additional

search subject to the warrant requirement.” Id. at 663–64

(Blackmun, J., dissenting, joined by Burger, C.J., and Powell

and Rehnquist, JJ.).

Four years after Walter, the Supreme Court again applied

the private search doctrine. Importantly, Jacobsen

recognized "the agreement [in Walter] on the standard to be

applied in evaluating the relationship between the two

searches.” 466 U.S. at 117 n.12.

Jacobsen concerned a government search of a Federal

Express ("FedEx”) package that had been partially opened

by FedEx employees. See 466 U.S. at 111. While examining

a damaged package, the FedEx employees "opened the

8 Justice Marshall concurred only in the judgment. Justice White,

joined by Justice Brennan, concurred, noting that "the packages already

had been opened, and the Government saw no more than what was

exposed to plain view.” Walter, 447 U.S. at 661 (White, J., concurring

in part and concurring in judgment). Although Justice Stevens

emphasized that the private parties had not screened the film, see id. at

657 & n.9, the concurring justices would have found a Fourth

Amendment violation even if the private parties had done so, as "a

private screening of the films would not have destroyed petitioners'

privacy interest in them.” Id. at 662.

18 UNITED STATES V. WILSON

package,” "cut open the tube” within the package, and

"found a series of four zip-lock plastic bags, the outermost

enclosing the other three and the innermost containing about

six and a half ounces of white powder.” Id. The employees

"observed . . . white powder in the innermost plastic bag,”

but did not open the (presumably transparent) bag. Id.

Instead, they called the Drug Enforcement Administration

(DEA), put the plastic bags back in the tube, and placed the

tube back in the box. Id.

When DEA agents arrived, they did two things: First, to

visually inspect the contents of the plastic bags, DEA agents

removed the tube from the box and the plastic bags from the

tube. See id. Second, federal agents "opened each of the four

bags and removed a trace of the white substance with a knife

blade.” Id. at 111–12. They performed a field test to

determine whether the powder in the plastic bags was

cocaine. See id.

Jacobsen considered whether the private search

exception as adopted by a majority of justices in Walter

applied to the facts at hand. In doing so, Jacobsen, like

Justice Stevens' opinion in Walter, looked at both the degree

to which the government's actions led to observing new

information not uncovered by the private search and the

extent to which the government's investigation intruded on

the package owner's privacy interests to a greater degree

than had the private party's actions. As to the first parameter,

the information gleaned by the government, Jacobsen

permitted the government agent to "reexamine”—that is,

examine in the same manner—the package previously

examined by FedEx, the private party. The government

"could utilize the [private] employees' testimony concerning

the contents of the package,” noted Jacobsen; "[p]rotecting

the risk of misdescription . . . is not protected by the Fourth

UNITED STATES V. WILSON 19

Amendment.” 466 U.S. at 119. As to the second parameter,

the additional impairment of privacy interests, Jacobsen

emphasized that the private search exception turns on parity

with the impact of the private search: "[O]nce frustration of

the original expectation of privacy occurs, the Fourth

Amendment does not prohibit governmental use of the nownonprivate information.” Id. at 117.

Applying these precepts, Jacobsen concluded that the

"removal of the plastic bags from the tube and the

[government] agent's visual inspection of their contents” did

not exceed the scope of the private search as to the

information obtained. Id. at 120. "[T]he agent[s] . . .

learn[ed] nothing [from those actions] that had not

previously been learned during the private search” and

conveyed to the federal agents by the FedEx employees. Id.

And as to the privacy interests, the governmental search to

that point "infringed no legitimate expectation of privacy

and hence was not a 'search' within the meaning of the

Fourth Amendment,” id., as "[t]he package itself, which had

previously been opened, remained unsealed, and the Federal

Express employees had invited the agents to examine its

contents,” such that "the package could no longer support

any expectation of privacy,” id. at 121.

Jacobsen then separately considered the chemical field

test, conducted by the DEA agents, including the federal

agents' removal of the white powder from the plastic bag.

Critically for our purposes, Jacobsen began this inquiry from

the premise that because the field test "had not been

conducted by the Federal Express agents,” it "therefore

exceeded the scope of the private search.” Id. at 122

(emphasis added). The majority then determined that the

government's chemical field test of the substance in the

properly seized plastic bags was nonetheless not a search

20 UNITED STATES V. WILSON

within the meaning of the Fourth Amendment, because

"governmental conduct that can reveal whether a substance

is cocaine, and no other arguably 'private' fact, compromises

no legitimate privacy interest.” Id. at 122–23. This

conclusion, Jacobsen explained, was "dictated” by the

Court's earlier decision in United States v. Place, 462 U.S.

696 (1983), "in which the Court held that subjecting luggage

to a 'sniff test' by a trained narcotics detection dog was not

a 'search' within the meaning of the Fourth Amendment.”

Jacobsen, 466 U.S. at 123.

B. Application of the Private Search Exception to

This Case

The government bears the burden to prove Agent

Thompson's warrantless search was justified by the private

search exception to the Fourth Amendment's warrant

requirement. Before considering the private search

exception, Coolidge emphasized "the most basic

constitutional rule” in the Fourth Amendment arena:

warrantless searches are per se unreasonable, subject to few

exceptions that are "jealously and carefully drawn.”

403 U.S. at 454–55. Accordingly, "[t]he burden is on those

seeking the exemption.” Id. at 455 (quoting United States v.

Jeffers, 342 U.S. 48, 51 (1951)). The government has not

met its burden here.

Both as to the information the government obtained and

the additional privacy interests implicated, the government's

actions here exceed the limits of the private search exception

as delineated in Walter and Jacobsen and their progeny.9

9 Wilson opines that the private search exception to the Fourth

Amendment should be overruled, and seeks to preserve that question for

any Supreme Court review of this case. As a court of appeals, we of

UNITED STATES V. WILSON 21

First, the government search exceeded the scope of the

antecedent private search because it allowed the government

to learn new, critical information that it used first to obtain a

warrant and then to prosecute Wilson. Second, the

government search also expanded the scope of the

antecedent private search because the government agent

viewed Wilson's email attachments even though no Google

employee—or other person—had done so, thereby

course cannot overrule Supreme Court cases. United States v. Weiland,

420 F.3d 1062, 1079 n.16 (9th Cir. 2005) ("[W]e are bound to follow a

controlling Supreme Court precedent until it is explicitly overruled by

that Court.”); accord Nunez-Reyes v. Holder, 646 F.3d 684, 692 (9th Cir.

2011). We do note that the private search doctrine rests directly on the

same precepts concerning the equivalence of private intrusions by

private parties and the government that underlie the so-called third-party

doctrine. See e.g., Smith v. Maryland, 442 U.S. 735, 744 (1979) (holding

that by "voluntarily” conveying to his telephone company the phone

numbers he dialed, the defendant forsook his reasonable expectation of

privacy in that information); United States v. Miller, 425 U.S. 435, 442

(1976) (holding the defendant lacked a reasonable expectation of privacy

in "information [he had] voluntarily conveyed to [his] bank[]” like

financial statements and deposit slips). In Jacobsen, the Supreme Court

reasoned that the private search exception follows from the premise,

underlying the third-party doctrine, that "when an individual reveals

private information to another, he assumes the risk that his confidant will

reveal that information to the authorities.” 466 U.S. at 117. In recent

years, however, the Court has refused to "mechanically apply[] the thirdparty doctrine,” stressing that "the fact of 'diminished privacy interests

does not mean that the Fourth Amendment falls out of the picture

entirely.'” Carpenter, 138 S. Ct. at 2219 (quoting Riley, 573 U.S. at 392);

see United States v. Jones, 565 U.S. 400, 417 (2012) (Sotomayor, J.,

concurring) (explaining that the third-party doctrine "is ill suited to the

digital age, in which people reveal a great deal of information about

themselves to third parties in the course of carrying out mundane tasks”);

Susan Freiwald & Stephen Wm. Smith, The Carpenter Chronicle: A

Near-Perfect Surveillance, 132 Harv. L. Rev. 205, 224 (2018) (noting

that Carpenter "significantly narrowed the [third-party] doctrine's

scope”).

22 UNITED STATES V. WILSON

exceeding any earlier privacy intrusion. Moreover, on the

limited evidentiary record, the government has not

established that what a Google employee previously viewed

were exact duplicates of Wilson's images. And, even if they

were duplicates, such viewing of others' digital

communications would not have violated Wilson's

expectation of privacy in his images, as Fourth Amendment

rights are personal.

1. Additional Information

The district court analogized Agent Thompson's review

of Wilson's email attachments to the government search in

Jacobsen, concluding that Agent Thompson's search

allowed him to "learn nothing new,” because Google had

already classified the images as child pornography. Wilson,

2017 WL 2733879, at *10–11. The government similarly

argues on appeal that its official search did not

impermissibly expand the scope of the private search

because it "just confirmed what Google employees already

knew and could say.” Both the district court's conclusion

and the governments' argument misstate the record.

The record indicates that Google does not keep a

repository of child pornography images, so no Google

employee could have shown the government the images it

believed to match Wilson's. Nor does the record identify the

individual who viewed those images in the repository, so no

identified Google employee "knew and could say” what

those images showed. Instead, Google keeps a repository of

unique hash values corresponding to illicit images, and tags

each image with one of four generic labels. All Google

communicated to NCMEC in its CyberTip was that the four

images Wilson uploaded to his email account matched

images previously identified by some Google employee at

some time in the past as child pornography and classified as

UNITED STATES V. WILSON 23

depicting a sex act involving a prepubescent minor (the "A1”

classification).10 Based only on the barebones CyberTip,

Agent Thompson testified, he opened and reviewed each of

Wilson's images to determine "whether or not it is a case

that . . . can be investigated” for violations of federal law.

A detailed description of the images was then included

in the applications for search warrants. The gulf between

what Agent Thompson knew about Wilson's images from

the CyberTip and what he subsequently learned is apparent

from those descriptions. In contrast to Google's label of the

images just as "A1,” which the government did not mention

in the warrant application, the government learned the

following:

1. 140005125216.jpg – This image depicts a

young nude girl, approximately five (5) to

nine (9) years of age, who is lying on her

stomach with her face in the nude genital

region of an older female who is seated with

her legs spread. A second young girl,

approximately five (5) to nine (9) years of

age, is also visible in this image and she is

partially nude with her vagina exposed.

Google identified this image was uploaded

on June 4, 2015, at 16:11:04 UTC.

2. 140005183260.jpg – This image depicts a

young nude girl, approximately five (5) to

nine (9) years of age, who is lying on top of

10 Perhaps a Google employee could also have testified to details

about the company's proprietary technology. But no such information

appears in the record, and the CyberTip did not convey any more

information than what is now included in the record.

24 UNITED STATES V. WILSON

an older nude female, approximately

eighteen years of age. Within this image the

girl's genital regions are pressed against one

another and the older girl appears to be

touching the face of the younger child with

her tongue. Google identified this image was

uploaded on June 4, 2015, at 16:11:21 UTC.

3. 140005129034.jpg – This image depicts a

partially nude young girl, approximately five

(5) to nine (9) years of age, who is lying on

her back with her legs spread and her vagina

exposed. An older female is positioned in

front of this girl's exposed vagina in this

image and the younger girl has her left hand

on the vaginal/buttocks area of a second nude

girl of similar age. Google identified this

image was uploaded on June 4, 2015, at

16:11:06 UTC.

4. 1400052000787.jpg – This image depicts

a wider angle view of the previously

referenced images possessing file names

140005125216.jpg and 140005129034.jpg as

reported by Google.

Wilson, 2017 WL 2733879, at *4–5.

Given the large gap between the information in the

CyberTip and the information the government obtained and

used to support the warrant application and to prosecute

Wilson, the government search in Walter offers a much more

apt comparison to the circumstances here than does the

government search in Jacobsen. Google's categorization of

Wilson's email attachments as "A1” functioned as a label for

UNITED STATES V. WILSON 25

the images in the same way that the boxes describing the

films in Walter suggested that the images on the films were

obscene. The "A1” labels, in fact, provided less information

about the images' contents than did the boxes in Walter,

which had "explicit descriptions of the contents” of the film.

447 U.S. at 652. The "A1” labels, in contrast, specified only

the general age of the child and the general nature of the acts

shown.

Viewing Wilson's email attachments—like viewing the

movie in Walter—substantively expanded the information

available to law enforcement far beyond what the label alone

conveyed, and was used to provide probable cause to search

further and to prosecute. The government learned at least

two things above and beyond the information conveyed by

the CyberTip by viewing Wilson's images: First, Agent

Thompson learned exactly what the image showed. Second,

Agent Thompson learned the image was in fact child

pornography. Until he viewed the images, they were at most

"suspected” child pornography. Just as it "was clearly

necessary for the FBI to screen the films [in Walter], which

the private party had not done, in order to obtain the evidence

needed to accomplish its law enforcement objectives,”

Walter, 447 U.S. at 659 n.14 (plurality), so here, to prosecute

Wilson it was necessary for Agent Thompson to view the

images no Google employee had opened. Id. Until Agent

Thompson viewed Wilson's images, no one involved in

enforcing the child pornography ban had seen them. Only by

viewing the images did the government confirm, and convey

to the fact finder in Wilson's criminal case, that they

depicted child pornography under the applicable federal

standard.

Importantly, the district court found—and we agree—

that if Agent Thompson's affidavit in support of a warrant

26 UNITED STATES V. WILSON

had been "excise[d]” of "the tainted evidence,” "the affidavit

would not support issuance of the search warrant for

Defendant's email account.” Wilson, 2017 WL 2733879,

at *12.11 The district court's findings about the inadequacy

of the warrant application without the important information

Agent Thompson obtained by viewing Wilson's images

demonstrate that the government learned new, critical

information by viewing Wilson's images, information "not

previously . . . learned during the private search,” Jacobsen,

466 U.S. at 120. Because the government saw more from its

search than the private party had seen, it exceeded the scope

of the private search.

2. Additional Intrusion on Wilson's Privacy

Interest

The government also maintains that directly viewing

Wilson's images for the first time was not a further invasion

of Wilson's privacy, beyond any privacy invasion by

Google. The government's expectation of privacy analysis

fails for much the same reason as did its argument that it

learned nothing new by viewing the images.

The government's central submission in this regard is

that Wilson's expectation of privacy in his images was fully

frustrated when Google's computer technology scanned

them, such that any further government search of the images

11 We also agree with the district court that the government might

have been able to demonstrate probable cause sufficient to obtain a

warrant without the descriptions of Wilson's images, by presenting, for

example, more "information about Google's screening process for child

pornography,” Wilson, 2017 WL 2733879, at *12.

UNITED STATES V. WILSON 27

should be exempt from the Fourth Amendment's warrant

requirement.12 We cannot agree.

Although Google's proprietary technology labelled

Wilson's email attachments as "A1,” "the content of the

[images] . . . was [no more] apparent” to Google than the

image content was to the private party in Walter, as no

Google employee had opened and viewed the attachments,

and Google does not appear to retain any record of the

original images used to generate hash matches. See Tosti,

733 F.3d at 823. Agent Thompson did not obtain a specific

description of the content of Wilson's attachments from

Google, so he was not simply confirming what he had been

told. Until he viewed the images, he had no image at hand at

all; the entire composition was hidden. Only the image itself

could reveal, for example, the number of minors depicted,

their identity, the number of adults depicted alongside the

minors, the setting, and the actual sexual acts depicted.

Reading a label affixed to an image is a different experience

entirely from looking at the image itself. To read even a

detailed description, which this A1 classification was not, is

still not to see. Wilson's privacy interest was in the actual

image—which could have included features in addition to

child pornography—not just in its classification as child

pornography.

The government's argument to the contrary

mischaracterizes the record, by representing that Google's

scan "equates to a full-color, high-definition view” of

Wilson's images. It does not. The critical fact is that no

Google employee viewed Wilson's files before Agent

12 The government stated at oral argument that it is not relying on

the contraband nature of child pornography as a justification for the

search.

28 UNITED STATES V. WILSON

Thompson did. When the government views anything other

than the specific materials that a private party saw during the

course of a private search, the government search exceeds

the scope of the private search. That is the clear holding of

Jacobsen. In that case, "[t]he field test . . . had not been

conducted by the Federal Express agents and therefore

exceeded the scope of the private search.” 466 U.S. at 122

(emphasis added); see supra Part II.B.1.

3. Personal Nature of the Fourth Amendment

The government attempts to save its warrantless search

by shifting the analysis from the private search of Wilson's

files, flagged by Google and classified as A1 by its

proprietary technology, to the private search of other

individuals' files, which some Google employee previously

viewed and classified as child pornography in Google's

database of hash values. The government argues that Agent

Thompson's search did not exceed the bounds of the private

search because a Google employee had previously viewed

different child pornography files, and Google's computers

flagged Wilson's email attachments as containing the same

images as those files, using an unspecified hash value

comparison system. This line of argument cannot save the

validity of the government's search. Even if Wilson's email

attachments were precise duplicates of different files a

Google employee had earlier reviewed and categorized as

child pornography, both Walter and Jacobsen—and general

Fourth Amendment principles—instruct that we must

specifically focus on the extent of Google's private search of

Wilson's effects, not of other individuals' belongings, to

assess whether "the additional invasions of [Wilson's]

privacy by the government agent . . . exceeded the scope of

the private search.” Jacobsen, 466 U.S. at 115.

UNITED STATES V. WILSON 29

To see why, consider whether Walter would have come

out differently had the misdirected package come into the

hands of someone who had previously viewed another copy

of the same film and, recognizing the box, told the police

that the film in it was, in her view, legally obscene. Under

Walter, the government in the hypothesized circumstance

would still need a warrant to view the film in the box.

Viewing the copy of the film actually in the box, which the

mistaken recipient of the box had not done, would still entail

an additional governmental intrusion on both the physical

integrity of the film and the owner's privacy interest in its

content.

Fourth Amendment rights are personal rights. Rakas v.

Illinois, 439 U.S. 128 (1978), is illustrative: Rakas held that

a passenger could not challenge a police search as violative

of the Fourth Amendment because he owned neither the

vehicle that was searched nor the rifle found. Although the

owners of each item had an expectation of privacy, the

defendant did not. See id. at 134.

So Wilson did not have an expectation of privacy in

other individuals' files, even if their files were identical to

his files. The corollary of this principle must also be true:

Wilson did have an expectation of privacy in his files, even

if others had identical files. If, for example, police officers

search someone else's house and find documents evidencing

wrongdoing along with notes indicating that I have identical

documents in my house, they cannot, without a warrant or

some distinct exception to the warrant requirement, seize my

copies. I would retain a personal expectation of privacy in

them, and in my connection to them, even if law enforcement

had a strong basis for anticipating what my copies would

contain. A violation of a third party's privacy has no bearing

30 UNITED STATES V. WILSON

on my reasonable expectation of privacy in my own

documents. The government does not argue otherwise.

In short, whether Google had previously reviewed, at

some earlier time, other individuals' files is not pertinent to

whether a private search eroded Wilson's expectation of

privacy. Under the private search doctrine, the Fourth

Amendment remains implicated "if the authorities use

information with respect to which the expectation of privacy

has not already been frustrated.” Jacobsen, 466 U.S. at 117

(emphasis added).

C. Relevant Appellate Caselaw

(i) Our application of Jacobsen and Walter is consistent

with Ninth Circuit case law. The district court misapplied

United States v. Tosti, 733 F.3d 816 (9th Cir. 2013), in

reaching the contrary conclusion.

In Tosti, a private party entrusted with the defendant's

computer found thumbnails of images believed to be child

pornography and alerted law enforcement officers. 733 F.3d

at 818–19. The private party showed the thumbnails to law

enforcement, and the agents "could tell from viewing the

thumbnails that the images contained child pornography.”

Id. at 822.

Tosti held that law enforcement's enlarging of the

thumbnails did not expand on the antecedent private search.

For one, based on the standard articulated in Jacobsen, "the

police learned nothing new through their actions.” Tosti,

733 F.3d at 822. Further, "scrolling through the images [the

private party] had already viewed was not a search because

any private interest in those images had been extinguished.”

Id.

UNITED STATES V. WILSON 31

Neither is true in this case. Here, what was conveyed to

Agent Thompson was that a not-yet-viewed image uploaded

by Wilson matched a different image that an unidentified

Google employee had previously viewed and classified as

child pornography. So until Agent Thompson actually

viewed the images, he knew only that Google's propriety

technology had identified a match between Wilson's images

and other images that Google had classified as child

pornography. He "learned . . . [a]new through [his] actions,”

for the first time, what the images actually showed. See

supra pp. 23–24. And, as no one at Google had previously

viewed Wilson's attachments, "any privacy interest in those

images had [not] been extinguished.” Tosti, 733 F.3d at 822.

Google's algorithm "frustrated [Wilson's] [privacy]

expectation in part,” but it "did not . . . strip the remaining

unfrustrated portion of that expectation of all Fourth

Amendment protection.” Walter 447 U.S. at 659 (plurality);

see also Jacobsen, 466 U.S. at 116 n.11.

For these reasons, Tosti is fully consistent with our

conclusion that Agent Thompson's search exceeded the

scope of the private search and so required a warrant.

(ii) In so holding, we contribute to a growing tension in

the circuits about the application of the private search

doctrine to the detection of child pornography.

In United States v. Ackerman, 831 F.3d 1292, 1294 (10th

Cir. 2016), AOL automatically identified one of the

defendant's four email attachments as apparent child

pornography, based on a hash value match. AOL then sent

the text of the defendant's email and all four attachments to

NCMEC, where an analyst "opened the email, viewed each

of the attached images, and confirmed that all four [images]

(not just the one AOL's automated filed identified) appeared

to be child pornography.” Id. Ackerman emphasized that

32 UNITED STATES V. WILSON

"AOL never opened the email itself. Only NCMEC did

that.” Id. at 1305–06. Then-Judge Gorsuch, after holding that

NCMEC is either a governmental entity or a government

agent, see id. at 1308, concluded that "in at least this way

[the government] exceeded rather than repeated AOL's

private search,” id. at 1305–06.

Ackerman did suggest that, had the government viewed

only the attachment AOL identified as a hash value match

and not other attachments and the text of the defendant's

email, that distinction might "bring the government closer to

a successful invocation of the private search doctrine.” Id.

at 1308 (emphasis added). But Ackerman also noted that in

that circumstance—which appears to be what happened

here—the government's action may still be a new search, as

the government, "might . . . have risked exposing new and

protected information, maybe because the hash value match

could have proven mistaken . . . or because the AOL

employee who identified the original image as child

pornography was mistaken in his assessment.” Id. at 1306.

Although Ackerman did not decide the precise issue before

us, and expressly disavowed "prejudg[ing]” it, id. at 1308–

09, its underlying analysis is entirely consistent with ours,

and its suggestions about why there could be a search in our

circumstances echo some of the reasons we have given for

so concluding.

Other private search cases concerning the discovery of

child pornography, outside the context of automated hash

value matching, have also ruled consistently with our

understanding of the limited scope of the private search

exception. For example, in United States v. Lichtenberger,

786 F.3d 478 (6th Cir. 2015), the defendant's girlfriend had

discovered child pornography on his computer. She later

showed his computer to the police and opened some

UNITED STATES V. WILSON 33

computer files that were determined to contain child

pornography. But the defendant's girlfriend was "not at all

sure whether she opened the same files with [the police] as

she had opened earlier that day.” Id. at 490. As a result, the

Sixth Circuit concluded that the government search

exceeded the scope of the private search. This reasoning

supports our result here. The record does not identify the

Google analyst who could have stated that the images Agent

Thompson viewed were identical to images the analyst

previously viewed, nor does it explain Google's algorithm in

any detail. Given these gaps, there is no way to be "at all

sure” that the images Agent Thompson viewed were the

same images a Google analyst had earlier viewed, so the

government search exceeded the scope of Google's search.

Further, in United States v. Sparks, 806 F.3d 1323 (11th

Cir. 2015), overruled on other grounds by United States v.

Ross, 963 F.3d 1056 (11th Cir. 2020), a store employee and

her fiancé discovered child pornography on a lost cell phone

and showed the phone to the police. The police officer

ultimately viewed two videos on the cell phone, one of

which the private parties "had not watched.” Id. at 1332.

Because the government search exposed new information,

not seen by the private party, the Eleventh Circuit concluded

that the government search exceeded the scope of the private

search.13

13 Both the Fifth Circuit and the Seventh Circuit have held that an

individual's privacy interest in a digital container, such as an email

account, cell phone, or laptop, is entirely frustrated whenever any part of

the container is searched. See United States v. Runyan, 275 F.3d 449, 465

(5th Cir. 2001); Rann v. Atchison, 689 F.3d 832 (7th Cir. 2012). But this

approach is squarely contrary to the Ninth Circuit's approach to digital

devices, has been undermined by more recent Supreme Court cases about

34 UNITED STATES V. WILSON

Conversely, the Fifth and Sixth Circuits recently decided

the issue before us and came to a conclusion contrary to the

one we reach, although the reasoning of the two opinions

diverged. The circumstances in both cases were similar to

those here. See United States v. Reddick, 900 F.3d 636 (5th

Cir. 2018); United States v. Miller, 982 F.3d 412, 427 (6th

Cir. 2020). In both cases, after an electronic service provider

flagged certain email attachments as apparent child

pornography, the attachments were forwarded to a local law

enforcement agency, whose officers viewed the images for

the first time without a warrant.

The Fifth Circuit held the private search exception

justified the government's warrantless search because the

government agent's "visual review of the suspect images . . .

the scope of digital information, and is inconsistent with Jacobsen. For

starters, Tosti did not regard the viewing of some files as sufficient for

purposes of the private search doctrine to show that the government only

invaded a defendant's privacy interests to the same extent as the private

party. See 733 F.3d at 822. More generally, and dispositively, the Ninth

Circuit has not treated digital devices as unitary, such that a permissible

search of one file or attachment justifies a search of a larger swatch of

digital material. See United States v. Cotterman, 709 F.3d 952 (9th Cir.

2013) (en banc); United States v. Cano, 934 F.3d 1002, 1007 (9th Cir.

2019). Further, Runyan and Rann are in tension with recent Supreme

Court cases, which express concern that given the "immense storage

capacity” of modern technology, the Fourth Amendment will be

undermined unless government searches of digital material are

meaningfully confined in accord with established Fourth Amendment

doctrine. Riley v. California, 573 U.S. 373, 393 (2014); see also

Carpenter v. United States, 138 S. Ct. 2206, 2214 (2018). Finally, if, in

Jacobsen, law enforcement officers had opened and searched not only

the specific containers investigated by the FedEx employees but others

included in the same box, the private search doctrine would not have

applied to the still-sealed containers. There is no basis for ruling

otherwise with regard to unopened digital files. Runyan and Rann were

in our view wrongly decided.

UNITED STATES V. WILSON 35

was akin to the government agents' decision to conduct

chemical tests on the white powder in Jacobsen,” insofar as

"opening the file merely confirmed that the flagged file was

indeed child pornography, as suspected.” Reddick, 900 F.3d

at 639.

We cannot accept this analysis for several reasons. First,

and most important, Reddick conflates Jacobsen's first

holding regarding the private search exception to the Fourth

Amendment with its second holding regarding whether the

field test constituted a search under the Fourth Amendment.

The private search exception excuses a warrantless

government search that would otherwise violate the Fourth

Amendment; the field test determination in Jacobsen, based

on Fourth Amendment law outside the private search

context, was that a warrantless government field drug test

simply does not trigger the Fourth Amendment's

protections. 466 U.S. at 123–24. In other words, the

warrantless chemical test in Jacobsen was not excused via

the private search exception but for an entirely different

reason—that confirming through a field test that an already

exposed and seized contraband substance was a drug is not

a search for Fourth Amendment purposes. Id. at 122.

Moreover, in Jacobsen, the white powder was fully

visible to the government officers when they repeated the

steps taken by the FedEx employees to inspect the package.

Not so here, as no human had viewed Wilson's images

before. The part of Jacobsen that does elucidate the private

search doctrine cannot govern here.

Notably, we have held that the chemical field test

exception to the Fourth Amendment's warrant requirement

does not apply to a more complete chemical analysis of a

drug. In United States v. Mulder, 808 F.2d 1346 (9th Cir.

1987), a hotel security officer removed items left behind in

36 UNITED STATES V. WILSON

a hotel room after a guest's scheduled departure, including

plastic bags full of tablets, and provided them to federal

agents. Id. at 1347. The tablets "were tested at the Western

Regional Laboratory through the use of mass spectrometry,

infrared spectroscopy and gas chromatography.” Id. at 1348.

Mulder distinguished between the chemical field test in

Jacobsen and a laboratory test: "[T]he chemical testing in

this case was not a field test which could merely disclose

whether or not the substance was a particular substance, but

was a series of tests designed to reveal the molecular

structure of a substance and indicate precisely what it is.

Because of the greater sophistication of these tests, they

could have revealed an arguably private fact,” and thus

compromised the defendant's legitimate privacy interest. Id.

at 1348–49.

To the extent opening an email attachment to view its

contents is analogous to drug testing at all, it is akin to a

laboratory test with the potential to reveal new private

information, as in Mulder, not a binary field test that yields

either a positive or negative result. Just as a laboratory test

of a suspected drug reveals its precise molecular structure

and so potentially exposes additional private information

like other illicit contaminants or the source of the substance,

so viewing an image of suspected child pornography reveals

innumerable granular private details—for example, the faces

of the people depicted, the setting, and, perhaps, other

speech or conduct also in the frame. Viewing the images

here allowed the government to do more than just confirm

the images' classification as child pornography, implicating

privacy interests beyond a binary classification. Contrary to

Reddick, the government's "visual review of the suspect

images” was not analogous to "the government agents'

decision to conduct chemical tests on the white powder in

Jacobsen.” 900 F.3d at 639 (emphasis added).

UNITED STATES V. WILSON 37

The Sixth Circuit recognized the error in Reddick

concerning the reach of the private search holding in

Jacobsen and "opt[ed] not to rely” on it. Miller, 982 F.3d

at 429. As Miller points out, the government agent's

"inspection (unlike the [field] test) qualifies as the invasion

of a 'legitimate privacy interest' unless Google's actions had

already frustrated the privacy interest in the files.” Id.

Miller instead resolved the Fourth Amendment question

it faced by focusing exclusively on the assumed reliability of

Google's proprietary technology. "At bottom,” Miller

explained, "this case turns on the question whether Google's

hash-value matching is sufficiently reliable.” Id. at 429–30.

Because the defendant in Miller "never challenged the

reliability of hashing,” id. at 430 (internal brackets and

quotation omitted) (Miller thought the burden was on the

defendant, see id. at 430), Miller deferred to the district

court's finding "that the technology was 'highly reliable.'”

Id.

Wilson, by contrast, did challenge the "accuracy and

reliability” of Google's hashing technology in the district

court. And, contrary to Miller's assertion, the government

bears the burden to prove its warrantless search was

permissible, see supra p. 20—a burden it failed to carry.

Our analysis, however, relies only contingently on the

adequacy of the record with regard to the hash match

technology. In our view, the critical factors in the private

search analysis, both unacknowledged in Miller, include the

personal nature of Fourth Amendment rights and the breadth

of essential information Agent Thompson obtained by

opening the attachment, information—and a privacy

invasion—well beyond what Google communicated to

NCMEC. See supra Parts II.B.1, II.B.2. The reliability of

Google's proprietary technology, in our estimation, is

38 UNITED STATES V. WILSON

pertinent to whether probable cause could be shown to

obtain a warrant, not to whether the private search doctrine

precludes the need for the warrant.

And, as the district court noted, and we have noted as

well, the warrant application here contained inadequate

information about Google's proprietary technology to

establish probable cause without reliance on the descriptions

of the actual images. See supra p. 25.

“When confronting new concerns wrought by digital

technology, this Court has been careful not to uncritically

extend existing precedents.” Carpenter, 138 S. Ct. at 2222.

The government reports there were 18.4 million CyberTips

in 2018, making it all the more important that we take care

that the automated scanning of email, and the automated

reporting of suspected illegal content, not undermine

individuals’ Fourth Amendment protections.

Having examined this case with the requisite care, we

hold, for the reasons explained, that Agent Thompson

violated Wilson’s Fourth Amendment right to be free from

unreasonable searches when he examined Wilson’s email

attachments without a warrant. Wilson’s conviction is

vacated, the district court’s denial of Wilson’s motion to

UNITED STATES V. WILSON 39

suppress is reversed, and this case is remanded for further

proceedings.14