FOR PUBLICATION

UNITED STATES COURT OF APPEALS

FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA, 

No. 04-10226 Plaintiff-Appellee,

D.C. No.

v.  CR-03-00062-1-HG

DANIEL KUUALOHA AUKAI,

OPINION Defendant-Appellant. 

Appeal from the United States District Court

for the District of Hawaii

Helen Gillmor, District Judge, Presiding

Argued and Submitted

May 11, 2005—Honolulu, Hawaii

Filed March 17, 2006

Before: Dorothy W. Nelson, Consuelo M. Callahan, and

Carlos T. Bea, Circuit Judges.

Opinion by Judge Bea

2837
COUNSEL

Edward H. Kubo, Jr., United States Attorney for the District

of Hawaii, and Thomas J. Brady, Assistant United States

Attorney for the District of Hawaii, for plaintiff-appellee the

United States of America. 

Pamela O’Leary Tower, Honolulu, Hawaii, for defendantappellant Daniel Kuualoha Aukai.

2840 UNITED STATES v. AUKAI
OPINION

BEA, Circuit Judge: 

We must decide whether a prospective commercial airline

passenger, who presented no identification at check-in, and

who voluntarily walked through a metal detector without setting off an alarm, can then prevent a government-ordered secondary screening search by stating he has decided not to fly

and wants to leave the terminal. We hold that such passenger

cannot prevent the secondary search because such search

comports with the Fourth Amendment’s requirement that a

search be reasonable where, as here, the initial screening was

“inconclusive” as defined in United States v. Torbet, 298 F.3d

1087, 1089-90 (9th Cir. 2002). We need not and therefore do

not decide whether the same would be true were the secondary screening more intrusive or were it triggered by the subjective evaluation of the prospective passenger by airline or

security personnel rather than more objective criteria such as

a screening machine alarm being triggered, random selection,

or, as here, the prospective passenger’s failure to present identification upon checking in.

I.

A.

On February 1, 2003, Defendant-Appellant Daniel Kuualoha Aukai arrived at the Honolulu International Airport

intending to take a Hawaiian Airlines flight from Honolulu,

Hawaii to Kona, Hawaii. He proceeded to check in at the

ticket counter, but did not produce a government-issued picture identification. Accordingly, the ticket agent wrote the

phrase “No ID” on Aukai’s boarding pass. 

Aukai then proceeded to the security checkpoint, where

signs were posted advising prospective passengers that they

and their carry-on baggage were subject to search. He entered

UNITED STATES v. AUKAI 2841
the security checkpoint at approximately 9:00 a.m., placed his

shoes and a few other items into a plastic bin, and then voluntarily walked through the metal detector or magnetometer.

The parties agree that the magnetometer did not signal the

presence of metal as Aukai walked through it. Nor did his

belongings trigger an alarm or otherwise raise suspicion as

they passed through the x-ray machine. After walking through

the magnetometer, Aukai presented his boarding pass to

Transportation Security Administration (“TSA”) Officer Corrine Motonaga. 

Pursuant to TSA procedures, a passenger who presents a

boarding pass on which “No ID” has been written is subject

to secondary screening even if he or she has passed through

the initial screening without triggering an alarm or otherwise

raising suspicion. As it was performed here, secondary

screening consists of a TSA officer passing a handheld magnetometer, known as a “wand,” near and around the passenger’s body. If the wand detects metal, it sounds an alarm. The

TSA officer then discerns the cause of the alarm, using techniques such as feeling the outside of the passenger’s clothes

in the area that caused the alarm and, if that area is near a

pocket, directing the passenger to empty his pocket. 

Because Aukai’s boarding pass had the “No ID” notation,

Motonaga directed Aukai to a nearby, roped-off area for secondary screening. Aukai initially complied, but complained

that he was in a hurry to catch his flight, which, according to

the boarding pass, was scheduled to leave at 9:05 a.m.

Although Aukai went to the roped-off area as directed, he did

not stay there. When Motonaga noticed that Aukai had left the

area and was gathering his belongings from the plastic bin,

she instructed Aukai that he was not allowed to retrieve his

property and that he had to stay in the roped-off area. 

Aukai then appealed to TSA Officer Andrew Misajon, who

was to perform the secondary screening, explaining again that

he was in a hurry to catch his flight. Misajon nonetheless had

2842 UNITED STATES v. AUKAI
Aukai sit in a chair, and thereafter proceeded to use the wand

to detect metal objects. At some point, Misajon had Aukai

stand, and when Misajon passed the wand across the front of

Aukai’s body, the wand alarm was triggered at Aukai’s front

right pants pocket. Misajon asked Aukai if he had anything in

his pocket, and Aukai responded that he did not. Misajon

passed the wand over the pocket a second time; again the

wand alarm was triggered. Misajon again inquired whether

Aukai had anything in his pocket; again Aukai said he did not.

Misajon then felt the outside of Aukai’s pocket and concluded

that something was inside the pocket. Misajon could also see

the outline of an unknown object in Aukai’s pocket. At some

point during this screening process, Aukai informed Misajon

that he wanted to leave the airport. 

At this point, TSA Supervisor Joseph Vizcarra approached

Misajon and asked whether he needed assistance. Misajon

related the events; Vizcarra asked Misajon to pass the wand

over Aukai’s pocket again. When the wand alarm again was

triggered, Vizcarra directed Aukai to empty his pocket. Aukai

again protested that he had nothing in his pocket. Using the

back of his hand, Vizcarra touched the outside of Aukai’s

pocket and felt something in the pocket. He again directed

Aukai to empty his pocket. This time Aukai reached into his

pocket and removed either his keys or change, but a bulge

was still visible in his pocket. Vizcarra directed Aukai to

remove all contents from his pocket. After claiming at first

that there was nothing more, Aukai finally removed an object

wrapped in some form of tissue paper and placed it on a tray

in front of him. 

Suspecting that the item might be a weapon, Vizcarra summoned a nearby law enforcement officer. Vizcarra then

unwrapped it and discovered a glass pipe used to smoke

methamphetamine. The law enforcement officer took control

and escorted Aukai to a small office near the security checkpoint. Aukai was placed under arrest and was searched incident to his arrest. During the search, the police discovered in

UNITED STATES v. AUKAI 2843
Aukai’s front pants pockets several transparent bags containing a white crystal substance. Aukai eventually was taken into

federal custody, where he was advised of and waived his

Miranda rights, and then gave a statement in which he inculpated himself in the possession of methamphetamine. 

B.

Five days later, Aukai was indicted for knowingly and

intentionally possessing, with the intent to distribute, 50

grams or more of methamphetamine, its salts, isomers, and

salts of its isomers, a Schedule II controlled substance, in violation of 21 U.S.C. §§ 841(a), 841(b)(1)(A)(viii). Aukai filed

a motion to suppress the evidence found incident to his arrest

at the airport and the statement he later made, which motion

the district court denied. Aukai then pleaded guilty pursuant

to a written plea agreement that preserved his right to appeal

the denial of his suppression motion. The district court sentenced Aukai to a term of imprisonment of 70 months and a

term of supervised release of 5 years, and Aukai timely

appealed. We have jurisdiction pursuant to 28 U.S.C. § 1291,

and affirm Aukai’s conviction. 

II.

We review de novo the district court’s legal basis for denying a motion to suppress, but review the district court’s findings of fact for clear error. United States v. Marquez, 410

F.3d 612, 615 (9th Cir. 2005), as amended by 2005 WL

1661572 (9th Cir. July 18, 2005). 

III.

[1] Federal law mandates that commercial airlines must

refuse to transport any prospective passengers who do not

submit to a search of their persons and possessions for dangerous weapons, explosives and other destructive devices

prior to boarding an aircraft. 49 U.S.C. § 44902. In United

2844 UNITED STATES v. AUKAI
States v. Davis, 482 F.2d 893 (9th Cir. 1973), we held that

such “nationwide anti-hijacking program[s,] conceived,

directed, and implemented by federal officials in cooperation

with air carriers,” are not “beyond the reach of the Fourth

Amendment.” Id. at 897. Nevertheless, we deemed these airport security screenings “administrative” searches to the

extent that they are “conducted as part of a general regulatory

scheme in furtherance of an administrative purpose, namely,

to prevent the carrying of weapons or explosives aboard aircraft, and thereby to prevent hijackings,” “rather than as part

of a criminal investigation to secure evidence of crime.” Id.

at 908. We held that, as “administrative” searches, airport

security screenings are “permissible under the Fourth Amendment though not supported by a showing of probable cause

directed to a particular place or person,” id., if, despite the

absence of a warrant, they nonetheless “meet the Fourth

Amendment’s standard of reasonableness.” Id. at 910. Finally,

we concluded that an airport security screening process satisfies this reasonableness standard provided “[1] that [it] is no

more extensive nor intensive than necessary, in the light of

current technology, to detect the presence of weapons or

explosives, [2] that it is confined in good faith to that purpose,

and [3] that potential passengers may avoid the search by

electing not to fly.” Id. at 913. 

At issue here is only the third element of the Davis test:

“[T]hat potential passengers may avoid the search by electing

not to fly.” Id. at 913; accord id. at 910-11 (“It follows that

airport screening searches are valid only if they recognize the

right of a person to avoid search by electing not to board the

aircraft.”); id. at 912 (“In sum, airport screening searches of

the persons and immediate possessions of potential passengers for weapons and explosives are reasonable under the

Fourth Amendment provided each prospective passenger

retains the right to leave rather than submit to the search.”).1,

1Aukai does not otherwise contest the lawfulness of the screening nor

of his subsequent arrest and the search incident to that arrest. In particular,

UNITED STATES v. AUKAI 2845
2

 In this regard, Aukai does not contest that he impliedly conAukai does not contend that his secondary screening violated either of the

Davis test’s two other necessary elements: that the screening was “no

more extensive nor intensive than necessary, in the light of current technology, to detect the presence of weapons or explosives,” and that it was

“confined in good faith to that purpose.” 

Regarding the former element involving the intrusiveness of the screening, Aukai does not contest the fact that he was not wanded after he had

removed his keys or change from his pocket and before being ordered to

remove from his pocket whatever it was that caused the visible and palpable bulge. See United States v. Pulido-Baquerizo, 800 F.2d 899, 901-02

(9th Cir. 1986) (holding that “a visual inspection and limited hand search

of luggage” that “is conducted in a manner which produces negligible

social stigma” “involves only a slight privacy intrusion”). 

Regarding the latter element involving the screening’s good faith limitation to its administrative purpose, Aukai does not contest that the screening was triggered by the objective criterion that he failed to present

identification upon his checking in at the airport. Therefore, this opinion

does not decide whether a secondary screening triggered solely by arbitrary and subjective criteria would be “confined in good faith to [detect the

presence of weapons or explosives],” and hence, a reasonable search under

the Fourth Amendment. See United States v. Henry, 615 F.2d 1223, 1228

(9th Cir. 1980) (reasoning that the non-discriminatory and objective nature

of the airport screening in question supported a finding that the screening

was “reasonable” apart and distinct from another necessary element of the

Davis test that the passenger impliedly consented to the screening); Davis,

482 F.2d at 910, 911 & n.51 (reasoning that an airport search was similar

to other administrative searches that did not require a warrant because it

was “ ‘not subject to the discretion of the official in the field,’ ” but also

requiring that passengers impliedly consent to such searches (quoting

Camara v. Municipal Court, 387 U.S. 523, 532 (1967)). 

2Although the third element of the Davis test speaks of “electing” not

to fly rather than “consenting” to the search, we recognized in Davis that

the two are opposite sides of the same coin: 

We have held that, as a matter of constitutional law, a prospective

passenger has a choice: he may submit to a search of his person

and immediate possessions as a condition to boarding; or he may

turn around and leave. If he chooses to proceed, that choice,

whether viewed as a relinquishment of an option to leave or an

election to submit to the search, is essentially a “consent,” granting the government a license to do what it would otherwise be

barred from doing by the Fourth Amendment.

2846 UNITED STATES v. AUKAI
sented to the initial metal detector screening and that such

screening complied with the third element of the Davis test.3

Instead, he argues that the secondary screening violated the

third element of the Davis test because, following his implied

consent to the initial screening, he elected not to fly rather

than undergo the secondary screening and, thereby, revoked

his implied consent. As noted above, the district court found

that Aukai informed Misajon that he wanted to leave the airport only “[a]t some point” during the secondary screening,

but before the methamphetamine pipe was discovered.

Indeed, the testimony from the hearing on Aukai’s motion to

suppress does not evince when Aukai declared his intent to

leave the airport. Nevertheless, we assume, as Aukai represents and as the government concedes, that Aukai declared his

election not to fly and his desire to leave the airport before the

wanding procedure.4 Our task, to which we now turn, is to

determine whether that election was valid. 

Davis, 482 F.2d at 913 (emphasis added); accord Henry, 615 F.2d at 1228

(9th Cir. 1980) (“We have interpreted Davis to require that the search be

reasonable and that there be ‘implied consent’ by the person to be

searched.”) (citing McMorris v. Alioto, 567 F.2d 897, 900 (9th Cir.

1978)); United States v. Homburg, 546 F.2d 1350, 1352 (9th Cir. 1976)

(“In [Davis], we held that the justification for warrantless screening

searches is the implied consent of the passenger.”). 

3Nor could he. See Marquez, 410 F.3d at 617-18 (“In this case, Marquez

checked in, went to the security checkpoint, waited in line, placed his bag

on the x-ray scanner, proceeded through the walkthrough magnetometer,

and allowed [the TSA officer] to begin screening his person with the handheld magnetometer; he had ample opportunity to choose to forego air

travel in order to avoid the screening.”); Davis, 482 F.2d at 914 (“It may

well be that under the present airport screening program, operating pursuant to current regulations, the alternatives presented to a potential passenger approaching the screening area are so self-evident that his election to

attempt to board necessarily manifests acquiescence in the initiation of the

screening process.”). 

4We note that after the wanding procedure began, Aukai claimed not to

have anything in his pockets on at least three occasions despite the wand

alarm having been triggered and, indeed, despite an obvious bulge in his

pocket. However, because this occurred after Aukai’s stated intention to

leave the airport, we do not address whether this behavior may have been

sufficiently suspicious to itself warrant at least a Terry stop-and-frisk. See

Terry v. Ohio, 392 U.S. 1, 27-30 (1968). 

UNITED STATES v. AUKAI 2847
A.

[2] Although we held in Davis that “airport screening

searches are valid only if they recognize the right of a person

to avoid [the] search by electing not to board the aircraft,” 482

F.2d at 910-11, we did not address when such a choice must

be made—that is, whether there is some stage during or after

which a prospective passenger may not withdraw his implied

consent to a search of his person or carry-on baggage by

electing not to fly. Pulido-Baquerizo, 800 F.2d at 902 (“Davis

did not determine at what point in the boarding process a passenger may decide not to fly and thereby withdraw his

implied consent.”); Homburg, 546 F.2d at 1352 (“Davis does

not state specifically that the consent to additional searches

after a preliminary screening may be revoked if a passenger

agrees not to board the plane.”). Following Davis, however,

we have addressed this question a number of times.

1.

On the one hand, we have implied in a number of cases that

a prospective passenger may elect not to fly so as to avoid a

search at any time.5

Thus, in United States v. Miner, 484 F.2d 1075, 1076 (9th

Cir. 1973), when the defendant attempted to check in for his

flight, one of the ticket agents determined that the defendant

fit the Federal Aviation Administration’s profile for airline

highjackers. Accordingly, airline employees escorted the

defendant to “a different area of the airport” that was “segregated from the normal boarding area,” and asked him to walk

through a magnetometer. Id. at 1076-77. The defendant

agreed. Id. at 1076. Although the magnetometer alarm was

5Of course, even under these cases, a prospective passenger who

revokes his consent may be lawfully subjected to a Terry stop-and-frisk

or, if supported by probable cause, a full search. E.g., Homburg, 546 F.2d

at 1352-54. 

2848 UNITED STATES v. AUKAI
not triggered, the airline employees nonetheless asked the

defendant to open a small suitcase that he was carrying. Id.

The defendant initially refused, but, after further requests,

eventually relented, at which point the airline employees

found amphetamine pills. Id. The district court denied the

defendant’s motion to suppress the evidence, and the defendant was convicted of possessing amphetamine pills with

intent to distribute in violation of 21 U.S.C. § 841(a)(1). Id.

We remanded so that the district court could conduct an

evidentiary hearing to determine whether the defendant’s ultimate acquiescence to the airline employees’ repeated requests

to search his suitcase was in fact voluntary rather than the

product of duress. Id. at 1077. In so doing, we explained that

although the defendant’s “approaching the counter with the

obvious intention of boarding a plane amounted to an implied

‘consent’ within the meaning of Davis,” his initial refusal to

consent to the search of his suitcase “was an apparent withdrawal of the implied ‘consent.’ ” Id. at 1076. Citing Davis,

we held: “At that point, the airline employees would have

been justified in refusing to permit him to fly, but they could

not compel him to submit to further search. Asking [him] to

open his suitcase could be justified only if he continued to

manifest an intention to board the plane, or if he otherwise

consented to the search.” Id. (internal citation omitted). 

Likewise, in United States v. Moore, 483 F.2d 1361, 1362

(9th Cir. 1973), the defendant attempted to check in for a

flight, but, in the opinion of a customs agent, could not satisfactorily identify himself as the person to whom the ticket had

been issued. Accordingly, he was told he would not be permitted to board the airplane, at which point the defendant

demanded the return of his two suitcases, which had already

been loaded onto the airplane. Id. at 1362-63. Upon retrieving

them, the defendant attempted to leave the terminal, but customs agents “drew him aside to an unoccupied boarding

area,” and searched a compartment within one of the suitcases

despite his refusal to permit them to do so. Id. at 1363. They

UNITED STATES v. AUKAI 2849
discovered marijuana. Id. The district court denied the defendant’s motion to suppress the evidence, and he was convicted

of possessing marijuana with the intent to distribute in violation of 21 U.S.C. § 841(a)(1). Id. at 1362. We reversed his

conviction, id. at 1364, holding in relevant part that the defendant’s “bag was not searched as part of an administrative

screening search of airline passengers’ carry-on luggage such

as was approved in [Davis],” in part because he “clearly indicated his desire to relinquish the opportunity to board the

flight before the search was made.” Id. at 1363. 

In United States v. Homburg, 546 F.2d 1350, 1351 (9th Cir.

1976), just before the defendant’s “carry-on suitcase was subjected to x-ray inspection and he went through the magnetometer” at a security checkpoint, airport officials were notified

of a bomb threat. As the defendant passed through the checkpoint, security officials noticed a rectangular bulge in the

front portion of the defendant’s pants. Id. After passing

through the checkpoint, the defendant went to a restroom and

was followed by a security officer. Id. The defendant “went

inside a toilet stall and the officer heard a ‘cracking or rustling

sound, like a plastic bag or something of that nature’ coming

from inside the toilet stall.” Id. (internal citation omitted).

Then, after about fifteen minutes, the defendant exited the

stall. Id. “[T]he bulge in his trousers was gone and he was carrying his suitcase normally. [The defendant] then took his

place in the boarding line, nervously watching security officers.” Id. A security officer approached the defendant and told

him that he would have to be “reinspected.” Id. The defendant

initially complied, but, upon returning to the security checkpoint, stated that he wished to leave the boarding area. Id. He

was then forcibly detained, and the security officers opened

the suitcase, finding heroin and cocaine within. Id. The defendant was charged with possession of heroin with the intent to

distribute in violation of 21 U.S.C. § 841(a)(1) and possession

of cocaine in violation of 21 U.S.C. § 844, and moved to suppress the evidence. Id. at 1351-52. The district court denied

the motion, and the defendant was convicted. Id.

2850 UNITED STATES v. AUKAI
On appeal, we affirmed on the grounds that the search was

justified as a Terry stop-and-frisk. Id. at 1352-54. However,

before doing so, we expressly considered and rejected the

notion that the defendant had consented to the search or otherwise relinquished Fourth Amendment protections merely by

passing through the security checkpoint and entering the

secured boarding area: 

The government argues that the search of [the

defendant] took place in what it terms a “critical

zone” which it compares to a border crossing and

where, it argues, “special Fourth Amendment considerations apply.” The government submits that

“once a passenger enters a secured boarding area, he

relinquishes any right to leave without being

searched if a security officer’s suspicions are

aroused.” The cases the government cites come primarily from the Fifth Circuit which does appear to

have adopted a view of airports as similar to border

crossings and qualitatively different from the home

or the street for Fourth Amendment purposes. 

While there is authority from this circuit to support the government’s view of airports generally [citing United States v. Doran, 482 F.2d 929, 931 n.1

(9th Cir. 1973)], we cannot accept the government’s

argument that a passenger in a secured boarding

area may not, as a general proposition, leave the

area rather than submit to additional searches. Such

a view runs contrary to the rationale of United States

v. Davis, 482 F.2d 893 (9th Cir. 1973). In that case,

we held that the justification for warrantless screening searches is the implied consent of the passenger.

“[A]s a matter of constitutional law,” we stated in

Davis, “a prospective passenger has a choice: he

may submit to a search of his person and immediate

possessions as a condition to boarding; or he may

turn around and leave.” 482 F.2d at 913. Davis does

UNITED STATES v. AUKAI 2851
not state specifically that the consent to additional

searches after a preliminary screening may be

revoked if a passenger agrees not to board the plane.

Id. at 1352 (emphasis added and citations omitted). In Homburg, we noted: 

Davis strongly indicates . . . that a party may revoke

his consent to be searched any time prior to boarding

the plane, even when he has passed beyond the initial screening point, if he agrees to leave the boarding area. Other decisions of this court have also

recognized that a passenger always maintains the

option of leaving. See, e.g., United States v. Miner,

484 F.2d 1075 (9th Cir. 1973); United States v.

Moore, 483 F.2d 1361 (9th Cir. 1973). We must

therefore reject the government’s view of its power

to search within the boarding area as too sweeping.

Since the undisputed evidence indicates that appellant wished to leave the boarding area, the trial judge

erred in finding the search reasonable under the general doctrine of implied consent. 

Id. at 1352. Nevertheless, we are not bound by this passage

because it is dicta. Indeed, the issue of implied consent to a

secondary search was irrelevant in Homburg because there,

authorities had reasonable suspicion to conduct a Terry stopand-frisk. Moreover, our more recent decisions have undercut

the reasoning of the quoted passage. See infra Section III.A.2.

Finally, in United States v. Henry, 615 F.2d 1223, 1225

(9th Cir. 1980), the defendant’s conduct while checking in at

the ticket counter aroused the ticket agent’s suspicion. So,

rather than allowing the defendant to check his briefcase at

the ticket counter, the agent told the defendant that he would

have to check his briefcase at the gate and, thus, pass his

briefcase through screening at the security checkpoint. Id.

There, the security officers ran the defendant’s briefcase

2852 UNITED STATES v. AUKAI
through the x-ray machine twice and saw some “dark

objects.” Id. When the security officers asked the defendant

to open his briefcase, he refused and was told that he would

have to take the briefcase back to the ticket counter and check

it as baggage. Id.

The defendant returned to the ticket counter, but the agent

took the briefcase and told the defendant to meet him back at

the security checkpoint. Id. at 1225-26. By the time the ticket

agent and his supervisor arrived at the security checkpoint, the

defendant had already gone to the boarding area. Id. at 1226.

The ticket agent and his supervisor left the briefcase at the

security checkpoint and proceeded to the boarding area,

where the supervisor told the defendant that unless he opened

the briefcase he could not take it with him. Id. “At this point

[the defendant] said, ‘I’ve got to have that bag in Dallas.

Okay.’ [The defendant] then turned away and boarded the

plane.” Id. Airline personnel then passed the briefcase through

the x-ray machine again, at which point a security agent said

she thought there might be a gun inside, and eventually forcibly opened the briefcase and discovered, among other things,

a loaded revolver. Id. The defendant was charged with knowingly delivering a briefcase in which there was a firearm to a

common carrier for shipment in interstate commerce without

giving written notice in violation of 18 U.S.C. §§ 922(e),

924(a), id. at 1225, and moved to suppress the evidence, id.

at 1227. The district court denied the motion, and the defendant was convicted. Id.

We affirmed the conviction, first concluding that the defendant had impliedly consented to the x-ray scans that took

place before he boarded the airplane because “he was free to

take the briefcase and leave the airport altogether or to board

without taking or checking the briefcase, rather than submit

it to the x-ray scan.” Id. at 1229. As for the later search, which

we characterized as “not [having been] conducted as part of

the program of screening passengers attempting to board,” id.,

we concluded that the defendant had consented when, after

UNITED STATES v. AUKAI 2853
being told that his briefcase would not be allowed on the

plane until it was searched, he said that he had to have the

briefcase at his destination and then boarded the plane, id. at

1230-31. In so doing, we implicitly held that the defendant’s

implied consent to the initial search did not compel him to

submit to all future searches. To the contrary, citing Davis, we

explained that the defendant’s consent to the search that took

place after he boarded was valid only to the extent it could

have been withdrawn. Id. Hence, although the defendant

never elected not to fly so as to avoid the later search, his ability to do so even after he passed through the security checkpoint was never in doubt, and was the basis of a finding that

his consent to the later search was freely given.6

2.

Despite these cases and the rather sweeping language in

Homburg that “Davis strongly indicates . . . that a party may

revoke his consent to be searched any time prior to boarding

the plane . . . if he agrees to leave the boarding area” and “that

a passenger always maintains the option of leaving,” Homburg, 546 F.2d at 1252, we nonetheless have held that under

certain circumstances a prospective passenger may not revoke

his consent even by electing not to fly. 

In United States v. Pulido-Baquerizo, 800 F.2d 899, 900

(9th Cir. 1986), the defendant approached the security checkpoint and placed two briefcases onto the x-ray machine’s conveyor belt. The security officer operating the x-ray machine

noticed an object within one of the briefcases that he thought

might be a bomb, but neither he nor the other security officers

6We note that Miner, Moore, Homburg and Henry were all decided

before September 11, 2001. However, we need not and therefore do not

decide whether the events of September 11, 2001, render those cases

anachronistic and, thus, whether the government’s interest in protecting

against terrorism by means of commercial airliners has so increased since

we decided these cases that we would now hold the searches there reasonable. 

2854 UNITED STATES v. AUKAI
could conclusively identify it as such. Id. They ran the briefcase through the x-ray machine a second time, but still could

not identify the object. Id. at 900-01. The officers then conducted a secondary hand search of the briefcase, which disclosed a large quantity of cocaine. Id. Prior to trial, the

defendant moved to suppress the evidence obtained by the

search and statements he made thereafter, and the district

court granted the motion. Id. at 901. 

We reversed. Id. at 900. In what was the first case to

address the question of when a passenger may revoke his consent by electing not to fly since Homburg and Henry, we

explained that “[w]hile Davis implies a passenger may withhold . . . consent [to secondary screening following an ‘inconclusive’ x-ray scan] by electing not to fly, Davis did not

determine at what point in the boarding process a passenger

may decide not to fly and thereby withdraw his implied consent” and, thus, “Davis does not specifically hold that consent

to an additional search could be withdrawn after an inconclusive x-ray scan if the passenger agreed not to board the

plane.” Id. at 902. We noted further that although “we refused

to adopt [in Homburg] a general doctrine of implied consent

in the context of airport luggage searches,” we nevertheless

“noted [in Henry] that the precise issue of whether implied

consent to a subsequent search existed by the mere fact of

placing luggage on the x-ray machine remained undecided.”

Id.

[3] Having set forth our understanding of our prior precedent, we then specifically rejected the defendant’s reliance on

Davis in arguing that he had made statements prior to the secondary search that “show[ed] he preferred to leave [the airport] rather than submit to the [secondary] search,” id. at 902,

and held:

[T]hose passengers placing luggage on an x-ray

machine’s conveyor belt for airplane travel at a

secured boarding area impliedly consent to a [secUNITED STATES v. AUKAI 2855
ondary] visual inspection and limited hand search of

their luggage if the x-ray scan is inconclusive in

determining whether the luggage contains weapons

or other dangerous objects. 

Id. at 901. Accordingly, “[t]he requirement in Davis of allowing passengers to avoid the search by electing not to fly does

not extend to a passenger who has already submitted his luggage for an x-ray scan” where the initial screening is “inconclusive,” and, “[t]hus, if a potential passenger [wishes] to

avoid a [secondary] search [in the event of an ‘inconclusive’

initial screening], he must elect not to fly before placing his

baggage on the x-ray machine’s conveyor belt.” Id. at 902. 

We note that Pulido-Baquerizo is not in direct conflict with

earlier cases such as Miner and Homburg, which stand for the

principle that prospective passengers can have the power to

limit their consent to airport searches even after voluntarily

submitting to initial screening procedures. The existence and

scope of implied consent must be examined in light of all the

circumstances, and such circumstances—and correlated societal expectations—may change over time. See Davis, 482

F.2d at 913 (noting that the burden on the defendant must be

measured against “the clear necessities of current circumstances”); Miner, 484 F.2d at 1076 (examining whether

implied consent existed in light of societal and individual contingencies, including that “concern over the problem of airplane hijacking was at its peak”). Earlier cases did not arise

in the context of now-familiar modern screening procedures,

in which the parallel use of magnetometer and x-ray scans is

practically ubiquitous, nor in the context of modern understandings about the class of objects that might present substantial danger on an airplane. See infra Section III.B.2. Our

holding in Pulido-Baquerizo with respect to the scope and

irrevocability of implied consent is consistent with the earlier

opinions in light of the changed circumstances, expectations,

and technology involved in modern air travel and airport

screening. See Pulido-Baquerizo, 800 F.2d at 901-02 (exam2856 UNITED STATES v. AUKAI
ining what “free society is willing to tolerate” in light of contemporary circumstances). 

Recently, in Torbet v. United Airlines, Inc., 298 F.3d 1087

(9th Cir. 2002), we revisited our holding in Pulido-Baquerizo.

Torbet walked through the magnetometer at a security checkpoint, and his carry-on bag passed through the x-ray machine,

all apparently without triggering an alarm or otherwise arousing suspicion. Id. at 1088. Nevertheless, acting pursuant to a

policy of randomly searching bags, even without the slightest

suspicion that a particular bag contained weapons or explosives, airport security personnel selected Torbet’s bag for

such a random search. Id. He refused to consent to the secondary search of his bag, stating instead that he wished simply to leave the airport. Id. Torbet was nevertheless detained,

and his bag was searched.7Id. The search revealed nothing of

note. Id. Pursuant to 42 U.S.C. § 1983, Torbet then sued the

airline, airport, and police officer that conducted the search,

alleging in relevant part that the random search to which he

had not consented violated his Fourth Amendment right

against unreasonable searches insofar as the initial screening

did not arouse suspicion that his bag contained weapons or

explosives. Id. at 1088-89. The defendants moved for judgment on the pleadings, which the district court granted. Id.

[4] We affirmed and held that a potential passenger irrevocably consents to a secondary screening when he voluntarily

submits to an initial screening that is “inconclusive” as to the

presence of weapons or explosives. Id. at 1089. We then interpreted the term “inconclusive” broadly:

[A]n x-ray scan may be deemed inconclusive, justifying further search, even when it doesn’t affirmatively reveal anything suspicious. “[F]irearms and

explosives can be small and easily concealed.” Con7Torbet’s person was not subjected to a secondary search. See Torbet,

298 F.3d at 1088. 

UNITED STATES v. AUKAI 2857
sequently, any x-ray scan that doesn’t rule out every

possibility of dangerous contents is, of necessity,

inconclusive. 

Id. at 1089-90 (emphases added) (internal citation omitted).8

Therefore, even when a secondary screening is triggered

solely as part of a systemized random search policy—the initial screening “doesn’t affirmatively reveal anything

suspicious”—the initial screening prohibits the potential passenger from revoking his implied consent for the secondary

screening if there still is a chance the passenger may be carrying as-yet-undetected weapons or explosives.9

 In other words,

the “inconclusive” nature of a proper initial screening, by

itself, establishes that the potential passenger has impliedly

consented to a secondary screening.10

8

In Torbet, we disagreed with the district court’s interpretation of

Pulido-Baquerizo “that consent to an x-ray scan [itself] implies consent to

further search, regardless of whether the x-ray scan is ‘inconclusive’ or

‘flatly devoid of suspicious features.’ ” Torbet, 298 F.3d at 1089. Rather,

given that current airport screening cannot rule out every possibility of

weapons or explosives, we clarified Pulido-Baquerizo to hold instead that

“an x-ray scan may be deemed inconclusive, justifying further search,

even when it doesn’t affirmatively reveal anything suspicious.” Id.

Because the currently accepted class of dangerous items is far broader

than what current screening technology could conclusively rule out, the

district court’s interpretation of Pulido-Baquerizo in Torbet and our interpretation of Pulido-Baquerizo currently have the same practical effect—

once a potential passenger voluntarily submits to an initial screening at an

airport, he or she cannot revoke consent to a secondary search. 

9We considered again the reasonableness of a random search during the

screening process at an airport security checkpoint in Marquez. 410 F.3d

at 616-18. However, we expressly did not consider whether the defendant

there elected not to fly so as to avoid the search, explaining that “[t]here

is no evidence before us that [he] ever changed his mind about flying to

Anchorage and that issue was neither briefed nor argued by the parties.”

Id. at 618. 

10Of course, a potential passenger does not impliedly consent to any and

all types of secondary search by submitting to an inconclusive initial

search. The scope of a potential passenger’s implied consent is circum2858 UNITED STATES v. AUKAI
B.

[5] Having now surveyed our relevant precedent, we conclude that the secondary screening at issue here is most akin

to that which we held reasonable in Torbet. Both here and in

Torbet, the contested search occurred at the security checkpoint, but after the prospective passenger had voluntarily

passed through initial screening, which, although it did not

“affirmatively reveal anything suspicious,” was nonetheless

“inconclusive” insofar as it did not “rule out every possibility

of dangerous contents.” Torbet, 298 F.3d at 1089-90. Accordingly, we follow the reasoning underlying Torbet in holding

that Aukai impliedly consented to a secondary search of his

person by walking through the magnetometer, and that he

could not subsequently revoke his consent to the secondary

screening. We recognize, of course, that the screening here

was different from that in Torbet in three respects: (1)

whereas the initial screening here was conducted by a magnetometer, the initial screening in Torbet was conducted by an

x-ray machine; (2) whereas the contested search here was of

Aukai himself, the contested search in Torbet was of the prospective passenger’s carry-on baggage rather than his person;

and (3) whereas the contested search here was triggered by

Aukai’s failure to present identification when checking in, the

contested search in Torbet was the product of random selection. Nonetheless, for the reasons explained below, we find

none of these differences of distinguishing significance. 

scribed by the Davis test’s two other necessary elements, neither of which

are at issue in this case: “that [the secondary search] is no more extensive

nor intensive than necessary, in light of current technology, to detect the

presence of weapons or explosives, [and] that it is confined in good faith

to that purpose.” 482 F.2d at 913. Unlike the criminal search context

where a court infers the scope of implied consent from the particular

details surrounding an individual’s exchange with an officer, see Florida

v. Jimeno, 500 U.S. 248, 251 (1991), the Davis test systematizes the

inquiry according to society’s privacy expectations in light of airport

searches’ broad regulatory policy of preventing terrorism, see PulidoBaquerizo, 800 F.2d at 901-02. 

UNITED STATES v. AUKAI 2859
1.

[6] As explained above, in Torbet, we defined “inconclusive” to encompass an x-ray scan that does not “affirmatively

reveal anything suspicious” insofar as it also does not “rule

out every possibility of dangerous contents.” Id. at 1089-90.

Thus, in Torbet, we upheld a secondary search resulting from

random selection, which, by definition, results in “searching

bags even without suspicion that a particular bag contained

weapons or explosives.” Id. at 1088. Nothing about this definition of “inconclusive” is necessarily limited to x-ray scans

as opposed to magnetometers. Rather, recognizing the limits

of current technology, see Davis, 482 F.2d at 913, we simply

acknowledged the fact that just because an x-ray machine

does not reveal weapons or explosives in a passenger’s carryon baggage does not mean that they are not there. Torbet, 298

F.3d at 1089-90; accord Pulido-Baquerizo, 800 F.2d at 901.

We find no reason to consider Aukai’s magnetometer search

any more conclusive than the x-ray scan at issue in Torbet. In

the first place, a magnetometer may allow small amounts of

metal through without alarming, either because the metal was

not detected or because the amount detected was below the

threshold at which the magnetometer alarms. Cf. Marquez,

410 F.3d at 617 (noting that a walkthrough magnetometer was

“less sensitive” than a handheld one); Doran, 482 F.2d at 930

(noting that a magnetometer was calibrated not to alarm for

small quantities of metal). Indeed, in the present case, the

metal objects that were (as it happens) in Aukai’s pockets did

not set off the walkthrough magnetometer’s alarm. More

important, it is hard to imagine how a magnetometer could

possibly detect prohibited items that do not contain metal. See

Permitted and Prohibited Items List, available at http://

www.tsa.gov/public/interapp/editorial/editorial_1012.xml

(listing among the prohibited items, for example, flammable

liquids, matches, and realistic replicas of certain prohibited

items). We therefore hold that, for the purposes of the implied

consent inquiry, the screening by the walkthrough magnetometer did not “rule out every possibility of dangerous contents”

2860 UNITED STATES v. AUKAI
and was therefore “inconclusive” under Torbet, 298 F.3d at

1089-90. 

2.

We similarly find that, under the rationale of our prior

opinions, Aukai’s arguments are not saved simply because it

was his person, rather than his baggage, that was subjected to

a secondary search. We recognize, of course, that a search of

a prospective passenger’s person may implicate greater privacy concerns than does a search of his carry-on baggage and,

thus, that there may be instances where particularly intrusive

searches of a prospective passenger’s person cannot be permitted even following “inconclusive” initial screening absent

consent, some particularized suspicion sufficient to justify a

Terry stop-and-frisk, or probable cause. However, like the

search in Pulido-Baquerizo, we believe that the magnetometer

scan and the subsequent search conducted here “involve[d]

only a slight privacy intrusion” that “we believe free society

is willing to tolerate,” because the “governmental interest in

detecting the weapons employed in airline terrorism is great”

and because the search was limited in scope to “the detection

of weapons, explosives, or any other dangerous devices and

[was] conducted in a manner which produces negligible social

stigma.” 800 F.2d at 901-02; see also Torbet, 298 F.3d at

1089-90. 

[7] There is no doubt that Aukai was on notice that his person could be searched. See Pulido-Baquerizo, 800 F.2d at 902

(requiring notice). Furthermore, the government interest is

just as great here as in the cases involving baggage searches.

Indeed, the events of September 11, 2001, have highlighted

that items a passenger could carry in his pocket may be just

as dangerous as what his carry-on baggage could contain. See,

e.g., National Commission on Terrorist Attacks Upon the

United States, The 9/11 Commission Report: Executive Summary (2004), available at 2004 WL 1846272, at *2 (noting

that terrorists “turned [four planes] into deadly guided misUNITED STATES v. AUKAI 2861
siles” using only “small knives, box cutters, and cans of Mace

or pepper spray”); see also Permitted and Prohibited Items

List, available at http://www.tsa.gov/public/interapp/editorial/

editorial_1012.xml (listing numerous prohibited items that are

pocket-sized). Moreover, the search itself involved “only a

slight privacy intrusion.” Pulido-Baquerizo, 800 F.2d at 901-

02. The security agents here used a wand to detect any metal

objects on Aukai’s person, patted the outside of Aukai’s pants

pockets, and directed Aukai to empty his pockets—all methods that were minimally intrusive to Aukai’s privacy in light

of his repeated non-cooperation. See Marquez, 410 F.3d at

616 (holding that a handheld magnetometer scan of a prospective passenger’s person was constitutionally permissible).

Finally, allowing a passenger in Aukai’s position to revoke

his consent prior to the secondary screening would, to the

same extent contemplated in Pulido-Baquerizo, “encourage

airline terrorism by providing a secure exit where detection

was threatened,” 800 F.2d at 902, and thus undermine the

essential deterrent purpose of such airport screenings. See

Davis, 482 F.2d at 908; Marquez, 410 F.3d at 617; see also

Torbet, 298 F.3d at 1090 (“[T]he Fourth Amendment does not

require that passengers be given a safe exit once detection is

threatened.”); Pulido-Baquerizo, 800 F.2d at 902 (noting that

an “airport screening agent has a duty to ferret out firearms

and explosive devices carried by passengers,” a duty that

“could not be fulfilled if the agent was prohibited from conducting a visual inspection and limited hand search after an

inconclusive x-ray scan”). In light of these concerns, the fact

that Aukai’s person was searched, rather than his baggage,

provides no basis for distinguishing the rule enunciated in

Pulido-Baquerizo and Torbet—namely, that implied consent

to an inconclusive initial search cannot be revoked prior to a

secondary search at a contemporary airport screening station.

3.

There is, of course, no question that our holding in Torbet

was in the context of a secondary screening that was the prod2862 UNITED STATES v. AUKAI
uct of random selection. Nevertheless, we do not find random

selection to be materially distinct from the trigger for secondary screening here—that is, Aukai’s failure to present identification upon checking in. Both depend on wholly objective

mechanisms for requiring secondary screening as opposed to

merely subjective evaluations by airline or security personnel.

By virtue of the objective criteria upon which they rely, both

suggest of themselves “the absence of any indicia of improper

motive.” Marquez, 410 F.3d at 618. Indeed, as with the random selection upheld in Torbet, we have expressly upheld the

constitutionality of subjecting airline passengers who lack

identification to a more thorough search. See Gilmore v. Gonzales, 435 F.3d 1125 (9th Cir. 2006). Hence, we need not and

therefore do not decide today whether a secondary screening

triggered by nothing more than the subjective evaluation of

the prospective passenger by airline or security personnel violates the Davis test’s requirement that an airport search be

“confined in good faith to [detect the presence of weapons or

explosives],” see 482 F.2d at 913, rather than more objective

criteria such as a screening machine alarm being triggered

(Doran), a screening machine otherwise signaling the possible

presence of weapons, explosives or other destructive devices

(Pulido-Baquerizo), random selection (Torbet), or, as here,

the prospective passenger’s failure to present identification

upon checking in. 

AFFIRMED. 

UNITED STATES v. AUKAI 2863