                 FOR PUBLICATION
 UNITED STATES COURT OF APPEALS
      FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA,                 No. 09-10504
               Plaintiff-Appellant,           D.C. No.
               v.                         1:08-cr-00513-
SIMON JASPER MCCARTY,                          JMS-1
              Defendant-Appellee.
                                            OPINION

        Appeal from the United States District Court
                 for the District of Hawaii
       J. Michael Seabright, District Judge, Presiding

                  Argued and Submitted
           October 14, 2010—Honolulu, Hawaii

                   Filed August 3, 2011

Before: Michael Daly Hawkins, M. Margaret McKeown and
          Johnnie B. Rawlinson, Circuit Judges.

                Opinion by Judge Hawkins




                           10007
                     UNITED STATES v. MCCARTY                     10011




                             COUNSEL

Vijay Shanker (argued) and David E. Hollar (briefed), United
States Department of Justice, Washington, D.C., for the
plaintiff-appellant.

William A. Harrison (argued and briefed), Davies Pacific
Center, Honolulu, Hawaii, for the defendant-appellee.


                              OPINION

HAWKINS, Senior Circuit Judge:

   The competing interests of personal privacy and the safety
of the traveling public are at the heart of this interlocutory
government appeal from the district court’s suppression of all
evidence obtained as a result of an airport search of defendant
Simon McCarty’s (“McCarty”) checked luggage at Hilo Inter-
national Airport. The government argues the evidence from
McCarty’s bag—which included, among other things, almost
five dozen photographs of nude and partially nude minors,1




  1
    Of the fifty-eight photographs discovered, fifty-seven were of minor
children in various states of undress. Eleven of the photographs depicted
fully nude children with exposed or partially covered genitals. United
States v. McCarty, 672 F. Supp. 2d 1085, 1092-1093 (D. Haw. 2009).
10012              UNITED STATES v. MCCARTY
children’s underwear and pajama advertisements, and hand-
written notes describing the molestation of children—was dis-
covered during the course of a properly limited administrative
search, the search was therefore lawful, and McCarty’s subse-
quent warrantless arrest was supported by probable cause.
McCarty contends, and the district court agreed, that Trans-
portation Security Administration (“TSA”) agents turned a
routine administrative search for explosives into an unautho-
rized investigatory search for contraband. We have jurisdic-
tion pursuant to 18 U.S.C. § 3731 and, for the following
reasons, vacate the suppression order and remand to the dis-
trict court for further proceedings.

                     STANDARD OF REVIEW

   “A district court’s conclusions of law regarding a motion to
suppress are reviewed de novo.” United States v. Hammett,
236 F.3d 1054, 1057 (9th Cir. 2001). Its factual findings are
reviewed for clear error. United States v. Aukai, 497 F.3d 955,
958 (9th Cir. 2007) (en banc). A finding of clear error
requires “a definite and firm conviction that a mistake has
been made. Thus, if the district court’s findings are plausible
in light of the record viewed in its entirety, the appellate court
cannot reverse even if it is convinced it would have found dif-
ferently.” Husain v. Olympic Airways, 316 F.3d 829, 835 (9th
Cir. 2002) (internal citations and quotation marks omitted).

                FACTS & PROCEEDINGS BELOW

A.     Facts

  1.    Preliminary Facts

   McCarty, a United Kingdom national, traveled to Hilo
International Airport to board an intrastate flight bound for
Honolulu on August 5, 2008. He checked two pieces of lug-
gage for the flight: (1) a “Travel Pro” brand bag; and (2) a
“Travel Zone” brand bag. The two bags were sent, as is cus-
                     UNITED STATES v. MCCARTY                     10013
tomary for all checked passenger baggage, to the TSA screen-
ing area, where TSA screeners Dorinda Andrade (“Andrade”)
and Jenny Moniz (“Moniz”) (who happens to be Andrade’s
daughter), were screening luggage for explosives using a
CTX 5500 DS security x-ray machine (“CTX machine” or
“CTX”). The Travel Zone bag passed through the machine
without incident, but the CTX machine produced an alarm on
the Travel Pro bag, signaling to Andrade that there was a
dense item in the bag requiring further inspection. The inspec-
tion that followed is the subject of this appeal.

  2.   CTX Machines and TSA Screening Policies

   TSA screens all luggage that goes onto a plane to ensure it
does not contain any explosive devices or other items that
would threaten the safety of the plane. One method of screen-
ing is through an x-ray device such as the CTX machine used
here, which can identify potential safety risks or dense items
in luggage that require further inspection. CTX machines
automatically stop the procession of bags through the screen-
ing area when they “alarm”2 on a potential safety hazard in a
bag; TSA screeners do not have the discretion or ability to
stop the machines themselves. Patrick Collins (“Collins”), the
Deputy Assistant Federal Security Director for TSA in charge
of operations at three Maui County airports, testified regard-
ing TSA procedures for searching checked luggage after the
CTX machine alerts on a particular bag. According to Collins,
when this occurs, the TSA screener is required to find and
examine the item identified by the machine to ensure it is not
an explosive device. For example, if the item is a laptop com-
puter, the screener must physically remove the laptop from
the luggage and examine it for the presence of hidden explo-
sives. A laptop may be used as a “decoy” or “distracter,”
  2
    TSA personnel used the word “alarm” as a verb throughout their testi-
mony, indicating that the CTX machine flagged the bag for further inspec-
tion. We adopt their usage of the word for the purposes of this Opinion,
and use it interchangeably with “alert.”
10014                 UNITED STATES v. MCCARTY
meant to distract the screener from continuing to search the
bag for explosives.

   Additionally, thin, flat explosives called “sheet explosives”
may be disguised as a simple piece of paper or cardboard, and
may be hidden in just about anything, including a laptop,
book, magazine, deck of cards, or packet of photographs. Col-
lins explained that where the CTX alarms on a dense mass
and the screener opens the bag to find a packet of photo-
graphs, the screener is required to leaf or thumb through the
stack of photographs until she is sure there are no sheet explo-
sives. She would not be required to closely examine those
items (by, for example, reading the contents of a written docu-
ment) unless she determined that they were “distracters.”

   Under TSA protocol, the search does not conclude until the
screener has cleared the bag of all safety concerns identified
by the CTX machine. According to Collins, “[t]he officer has
to be satisfied that there’s nothing else in that bag that could
have caused that alarm. And they take whatever procedure
they have to to find that.” In some cases, this may require
going as far as removing the lining of the bag to ensure that
no possible explosives remain. Adherence to the protocol is
mandatory, not discretionary, although the determination of
whether any further safety concerns exist after a preliminary
search is committed to the discretion of the screener. The
screener is to end the search once she is satisfied that she has
followed the protocol and removed all safety concerns.

   TSA screeners do not have any training in identifying con-
traband, and they are not directed by any policy to perform
searches for contraband. The screener’s sole job is to clear
bags of safety concerns relating to air travel. However, if, in
the course of searching for explosives, a screener finds an
item she believes to be contraband, she is required by TSA
Operations Directive OD-400-54-2 to call a law enforcement
officer.3 It is not the screener’s job to continue investigation
  3
    The item need not actually be contraband; Collins testified that screen-
ers are required under the TSA policy to notify a law enforcement officer
                      UNITED STATES v. MCCARTY                       10015
of possible contraband found in the course of an administra-
tive safety inspection.

  3.    The Search

   The CTX alerted on McCarty’s Travel Pro bag at 10:13
a.m., flagging as a possible safety concern what appeared to
be a laptop with a dark mass around it.4 Andrade could not tell
what the dark mass was by looking at the CTX image, so she
released the bag from the machine and placed it on a search
table for manual inspection.

   Based on the weight of the bag, Andrade determined that
the laptop was in the top pocket. She unzipped the pocket
halfway and pulled out the laptop with one hand. As she did
so, another bag passed through the CTX machine, and
Andrade turned her head to watch the machine’s screen while
that bag passed through. When she turned back to the table,
she noticed that an envelope had also slid out of the bag with
the laptop, spilling some of the envelope’s contents. Andrade
testified that “a couple of pictures” were “laid open on the
table,” although she clarified that by “a couple” she meant
that more than ten photographs were visible. The precise
arrangement of the photographs on the table is unclear.

   Andrade took approximately one minute to clear the laptop
pursuant to TSA protocol before turning to the photographs
and other spilled items. She noted that, after searching the lap-
top, she needed to find the dark mass shown in the CTX
image, which she believed could be the photographs on the
table. Andrade could not “precisely say what photographs”

and turn the item over for further action if they simply “feel it possibly
could be contraband.” McCarty does not challenge the TSA policy on this
matter.
  4
    When a CTX alerts, it identifies possible safety threats by placing a red
box on the screen, framing the possible problem item.
10016             UNITED STATES v. MCCARTY
were immediately visible when they first spilled out, but she
did remember seeing photos of nude children, including one
of a boy on a bed with his eyes closed.5 She inspected the
photographs that had spilled out of the envelope onto the
table. She then proceeded to look through less than half of the
photographs from the envelope, specifically because she
needed to clear the contents of the envelope of any safety haz-
ards that might be hidden between the photos. She stopped
short of looking through every photograph in the envelope
once she was satisfied there were no safety issues, and
because she did not want to see any more of the photographs.
Then, although she was no longer concerned about explosives
and felt that the “pictures that [she] saw [were] enough to
make [her] determine that the children weren’t in a good situ-
ation,” Andrade proceeded to read a few lines of the letters in
the envelope to “determine what the pictures were all about”
and to “make sure” that the photographs were contraband
before she called her lead officer to report them. She also
viewed the advertisements and two newspaper article clip-
pings discussing minors engaging in sexual activity with
adults and other minors.

   At some point during this inspection, Andrade said out
loud, “what the heck is this?” Moniz, who was also present
in the room, came over to see what caused Andrade’s reac-
tion. She helped Andrade pick up the contents of the enve-
lope, and her initial impression upon seeing the visible photos
was that there was something “wrong.” Moniz testified that
while the two were collecting the photos that spilled out of the
envelope, “at that point we saw something that was improper,
we did look through the rest of them, and then we stopped.”
During this process, she saw newspaper articles, some chil-
dren’s underwear advertisements, and a letter. Moniz read a
few lines of the letter and showed Andrade the underwear ads.
Moniz specifically testified to seeing photographs of a nude
  5
  It was unclear whether Andrade saw this photograph initially or
whether she saw it later on in the course of her search.
                    UNITED STATES v. MCCARTY                     10017
boy in a pond setting and another of a boy laying on a bed
with his eyes “squinted shut to hold it shut like he was very
uncomfortable,” but she could not recall whether these photo-
graphs were among the first she saw before she and Andrade
looked through the contents of the envelope. Although Moniz
recalled seeing “a lot” of images that looked “improper” to
her, she could not identify exactly which of the fifty-eight
photographs she saw.6

   Tracy Kitamura (“Kitamura”), the lead on-site TSA
screener, was already in the room when Andrade and Moniz
were looking through the contents of the envelope. Andrade
called him over, although it is somewhat unclear whether she
did so before or after she and Moniz proceeded to look
through the non-photographic items in the envelope, and
whether Kitamura was already heading over to the table after
hearing Andrade’s exclamation. Kitamura briefly leafed
through the photographs that were on the table and immedi-
ately felt sick to his stomach because “[t]he photos were very
disturbing initially.” He did not read the letters. The first pho-
tos he saw were of nude children, and he also saw photos of
partially clad children. He then immediately called in the Hilo
TSA Supervisor, Stephanie Kamohai (“Kamohai”). Kamohai
shuffled through the contents of the envelope, including the
photographs and newspaper clippings, without reading or
closely examining them. She read three or four lines of the
letter. Within fifteen seconds of viewing the items, Kamohai
decided to call a law enforcement officer based solely on the
photographs she had seen.
  6
   At the direction of the TSA supervisor, Moniz also performed a full
search for explosives on McCarty’s other bag, which had already cleared
the TSA safety inspection and which had not produced any alarm upon
passing through the CTX machine. During the course of that search,
Moniz flipped through the pages of a journal in the second bag, and read
one page that caught her attention. The government does not contest sup-
pression of any evidence found in the second bag.
10018             UNITED STATES v. MCCARTY
   Just before 10:20 a.m., less than seven minutes after the
CTX alarmed on McCarty’s bag, Kamohai called Rodney
Aurello (“Aurello”), a private security contractor working
with the Hawaii Department of Transportation, who was
assigned to Hilo airport. Aurello thumbed through the photo-
graphs. He testified that, based on his background working in
the “juvenile age section,” he “thought it was kind of suspi-
cious that [McCarty] would have all of these photographs,
especially of the nude minors,” and immediately decided to
call his supervisor to suggest calling the police.

   Two Hawaii County Police Department officers, including
Detective Norbert Serrao (“Serrao”), responded less than
twenty minutes later. Serrao spent two to three minutes exam-
ining the photographs, but did not read all the articles or the
letters. Based on what he saw, Serrao decided to arrest
McCarty for promotion of child abuse in violation of Hawaii
Revised Statutes § 707-752.

   After McCarty’s arrest, Detective John Ancheta
(“Ancheta”) interviewed him at the Hilo Police Department.
Ancheta explained that, based on his discussions with other
officers, he believed he had enough evidence to arrest
McCarty for possession of child pornography. He then asked
McCarty for consent to search his luggage. Ancheta explained
McCarty’s options, including the right to refuse consent to the
search. McCarty initialed and signed a consent form for the
search. Ancheta also read McCarty his Miranda rights, which
McCarty waived by initialing a fully completed Advice of
Rights form stating that he understood the rights he was read,
that he did not want a lawyer, and that he would like to speak
with Detective Ancheta about what had happened. After
waiving these rights, McCarty was interviewed and admitted
to having unnatural feelings about children for some time, but
denied ever acting on those feelings.

   McCarty was arrested two days later on a federal com-
plaint. Federal agents obtained a search warrant for McCar-
                     UNITED STATES v. MCCARTY                       10019
ty’s laptop computer, on which they discovered hundreds of
images and at least 200 video clips of child pornography.
Sixty of these video clips depicted McCarty engaged in sexual
activity with at least three different prepubescent boys.

B.    Procedural History

   A grand jury returned a 10-count second superseding
indictment against McCarty on January 21, 2009. The indict-
ment alleged: two counts of transportation of child pornogra-
phy in violation of 18 U.S.C. § 2252A(a)(1); two counts of
possession of child pornography in violation of 18 U.S.C.
§ 2252A(a)(5)(B); and six counts relating to coercing minors
to engage in sexually explicit conduct outside the United
States for the purpose of producing a visual depiction of that
conduct, and transporting those visual depictions to the
United States, in violation of 18 U.S.C. § 2251(c)(1)(B).
McCarty filed a motion to suppress all evidence obtained as
a result of the airport search of his checked luggage.

   After briefing and a suppression hearing, the district court
granted McCarty’s motion and ordered all evidence seized as
a result of the airport search of his luggage suppressed.
McCarty, 672 F. Supp. 2d at 1090. The court ultimately found
that “Andrade’s search of the Travel Pro bag went beyond the
scope of an airport administrative search for weapons and/or
explosives and that her vague and contradictory testimony
regarding what items she found during her administrative
search are insufficient to support probable cause [to arrest
McCarty].” Id. at 1095.7 Concluding McCarty had therefore
been arrested without probable cause, the district court deter-
mined that any evidence obtained during the subsequent con-
sent and warrant-based searches was fruit of the poisonous
tree. Id. at 1103-04.
  7
    The parties agreed that McCarty’s arrest would have been valid only
if the administrative search produced probable cause to believe he had vio-
lated Haw. Rev. Stat. § 707-752. McCarty, 672 F. Supp. 2d at 1095.
10020                 UNITED STATES v. MCCARTY
   In reaching these conclusions, the district court described
the sequence of events, noting with particular frustration that
Andrade’s testimony was confusing and contradictory at sev-
eral points,8 including as to the exact chronology of events,
which photographs she had seen, and whether she or Moniz
touched any of the items that had spilled onto the table before
the lead officer was called. Id. at 1092-95. The court stated
that it could not discern exactly what Andrade and Moniz
inspected, or when they inspected it. Id. at 1093.

   Acknowledging that TSA screeners could legally search the
bag for evidence of explosives, and that Andrade had begun
her search with this permissible search intent in mind, the dis-
trict court began its legal analysis by noting that “Andrade’s
inadvertent discovery of some of the photographs did not of
itself extend the search beyond its valid purpose.” Id. at 1096
(citing United States v. Marquez, 410 F.3d 612, 617 (9th Cir.
2005) (“The mere fact that a screening procedure ultimately
reveals contraband other than weapons or explosives does not
render it unreasonable, post facto.”)). Nonetheless, it then
stated,
  8
    Andrade’s testimony as to her perceptions and impressions of the pho-
tographs and other items certainly was confusing and somewhat contradic-
tory, evidencing that Andrade did not subjectively think she had enough
evidence of contraband to call law enforcement until she had seen more
than just the first few photographs. She testified that she did not know
something was wrong when she saw just the first nude photographs, Dis-
trict Court Docket (“DCD”) #57 at 63, but after seeing the initial photo-
graphs that spilled out of the bag, “the pictures that [she] saw [were]
enough to make [her] determine that the children weren’t in a good situa-
tion,” id. at 62. She “felt some concern” immediately after seeing nude
photographs, id. at 70, and “felt that the children were in a harmful way”
after leafing through the photos in the envelope, but she read through
some of the letters because she “felt that [she] needed to see more than
what [she] saw before [she] called [her] lead,” id. at 62. She also said that
she was alarmed “as soon as [she and Moniz] saw the pictures,” and that
is why she called Kitamura, id. at 75, yet she finally decided that there was
something wrong only after taking “everything combined together,”
including the non-photographic items from the envelope. Id. at 76-77.
                  UNITED STATES v. MCCARTY                 10021
    [t]he court cannot conclude . . . that the search of the
    Travel Pro bag was limited to ensuring that it did not
    pose a safety risk. Rather, the testimony evidences
    that the TSA employees, at some point, clearly
    exceeded the scope of their administrative search
    and began to search for evidence of child pornogra-
    phy.

Id. Accordingly, the district court found that the government
had not carried its burden of proving that the search had been
“confined in good faith” to the purpose of detecting explo-
sives. See id. at 1096-99 (citing Aukai, 497 F.3d at 962).

   The district court explained that, “based on [Andrade’s]
demeanor and testimony provided, the court easily concludes
that she was not credible.” Id. at 1096. It clarified that it was
not suggesting that Andrade had perjured herself, but merely
that she could not clearly recall what had happened with suffi-
cient clarity. Id. at 1096 n.7. The court based its credibility
determination on inconsistencies in Andrade’s testimony,
placing emphasis on Andrade’s statements that her focus was
solely on the safety of the children when she read the content
of articles and letters from the envelope. Id. at 1096-97.

   Based on these statements, its assessment of Andrade’s
credibility, and testimony of other witnesses, the court “spe-
cifically [found] that Andrade searched the photographs in the
envelope not for sheet explosives but for evidence of child
pornography.” Id. at 1097 n.8; see also id. at 1098 n.9 (find-
ing that TSA screeners did not leaf through photographs for
evidence of sheet explosives, “but instead inspected them for
their content”).

  Having so found, the district court stated that even if
Andrade had continued her inspection for the dual purposes
of detecting explosives and determining whether the photos
were contraband—which it did not believe was the case—the
secondary purpose unrelated to administrative safety concerns
10022                 UNITED STATES v. MCCARTY
would have invalidated the otherwise permissible search
because the TSA screeners “had discretion in deciding how
closely to look at the photographs and indeed, rather than
‘leaf’ through them for sheet explosives, inspected them
solely to determine whether the children were in harm’s way.”
Id. at 1097-98 (citing United States v. Bulacan, 156 F.3d 963,
969 (9th Cir. 1998), for the proposition that an impermissible
search motive invalidates an otherwise lawful administrative
search). However, the court ultimately clarified that it did not
believe the extended search was one of dual purpose, but
rather one where the administrative search was wholly super-
seded by the investigative search for evidence of child por-
nography. Id. at 1098 n.9.

   The court then specifically rejected the government’s argu-
ment that the search conducted was proper regardless of
motive because Andrade was required by the TSA protocol to
leaf or thumb through the photographs to search for sheet
explosives, reiterating its finding that Andrade and Moniz “in-
spected the content of additional photographs for the purpose
of determining their criminal nature.” Id. at 1098.

   Turning to the question of probable cause for the warrant-
less arrest, the district court found that because Andrade’s tes-
timony had not clarified exactly which photos she had seen
while she was still searching for explosives, the government
failed to prove that Andrade had discovered evidence support-
ing probable cause to arrest McCarty during the lawful por-
tion of the search. Id. at 1099-1102. In so finding, the court
emphasized that at least three of the fifty-seven photographs
of children were clearly not child pornography, and since nei-
ther Andrade nor Moniz could identify exactly which of the
photographs she saw when the envelope first spilled onto the
table9 (which the court had apparently concluded was the end
  9
   The court stated, “even if the court credits Andrade’s testimony that
she initially saw photographs of nude children (which the court does not),”
such testimony could not, on its own, establish probable cause. Id. at 1100.
                     UNITED STATES v. MCCARTY                       10023
point for the lawful administrative search), it could not deter-
mine that either screener had seen any photos giving rise to
probable cause during the lawful administrative search. Id. at
1100-02.10 Specifically, the court held that

       without knowing which photographs of nude chil-
       dren Andrade saw, the probable cause determination
       cannot be supported unless all of these photographs
       constitute child pornography—if only some of the
       photographs of nude children are child pornography,
       the court has no way of knowing whether Andrade
       initially saw those photographs as opposed to the
       photographs that are not child pornography.

Id. at 1100.

   The court also held that the lack of specificity in Andrade’s
testimony meant that the government could not establish the
“immediately apparent” incriminating nature of the photo-
graphs, and thus the plain view doctrine could not apply. Id.
at 1098-99. It then found that the exception for good faith
mistakes outlined in Herring v. United States, 555 U.S. 135
(2009), did not apply to bar suppression in this case. McCarty,
672 F. Supp. 2d at 1102-03.11

  Lastly, the district court held that, assuming McCarty’s
consent to search of his luggage at the police station was vol-
untary, the government could not prove the consent was
purged of the primary taint of the original unlawful search,
and suppression could not be avoided. See id. at 1103-04.12
  10
      The court did not, however, make any determination as to whether any
of the remaining photographs constituted child pornography or could have
provided probable cause to believe they were child pornography.
   11
      The government did not challenge the district court’s ruling on the
Herring exception on appeal, so we do not review it here.
   12
      The government also did not dispute this ruling, so the issue of the
effect of McCarty’s consent to search at the police station is likewise not
before us.
10024                UNITED STATES v. MCCARTY
     The government appealed.

                              DISCUSSION

A.     Scope of the Lawful Administrative Search

   [1] The Fourth Amendment protects against unreasonable
searches and seizures of people and their effects. U.S. Const.
amend. IV. Searches and seizures are “ ‘ordinarily unreason-
able in the absence of individualized suspicion of wrongdo-
ing,’ ” Aukai, 497 F.3d at 958 (quoting City of Indianapolis
v. Edmond, 531 U.S. 32, 37 (2000)), and the circumstances
under which a warrantless search not supported by probable
cause may be considered reasonable under the Fourth Amend-
ment are very limited, see id.; United States v. Caseres, 533
F.3d 1064, 1070 (9th Cir. 2008) (citing Katz v. United States,
389 U.S. 347, 357 (1967)).

   [2] Blanket suspicionless searches “calibrated to [a] risk
may rank as ‘reasonable.’ ” Aukai, 497 F.3d at 958 (internal
quotation marks omitted) (quoting Chandler v. Miller, 520
U.S. 305, 323 (1997)). For example, if properly limited,
“searches now routine at airports and at entrances to courts,”
are reasonable because they respond to a “ ‘risk to public
safety [that] is substantial and real.’ ” Id. (quoting Chandler,
520 U.S. at 323). Generally, “airport screening searches . . .
are constitutionally reasonable administrative searches
because 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 air-
craft, and thereby to prevent hijackings.’ ” Id. at 960 (quoting
United States v. Davis, 482 F.2d 893, 908 (9th Cir. 1973)).13
  13
    Aukai cautions that “[t]he Supreme Court has not specifically held that
airport screening searches are constitutionally reasonable administrative
searches,” but rather has suggested that they qualify as such. 497 F.3d at
959 n.2 (collecting cases).
                     UNITED STATES v. MCCARTY                      10025
   [3] Here, the parties agree that, under federal law, TSA
agents could legally search McCarty’s entire bag for explo-
sives or other safety hazards. See 49 U.S.C. § 44901; cf. 49
C.F.R. § 1540.111(c) (prohibiting passengers from placing
unauthorized explosives, firearms, and incendiary devices in
their checked baggage). However, because warrantless, suspi-
cionless administrative searches remain subject to the Fourth
Amendment, a particular search is “constitutionally reason-
able [only where] it ‘is no more extensive nor intensive than
necessary, in the light of current technology, to detect the
presence of weapons or explosives [and where] it is confined
in good faith to that purpose.’ ” Aukai, 497 F.3d at 962 (quot-
ing Davis, 482 F.2d at 913).

   [4] In other words, an airport search remains a valid
administrative search only so long as the scope of the admin-
istrative search exception is not exceeded; “once a search is
conducted for a criminal investigatory purpose, it can no lon-
ger be justified under an administrative search rationale.”
United States v. $124,570 U.S. Currency, 873 F.2d 1240,
1246 n.5 (9th Cir. 1989). Thus, because TSA screeners are
limited to the single administrative goal of searching for pos-
sible safety threats related to explosives, the constitutional
bounds of an airport administrative search require that the
individual screener’s actions be no more intrusive than neces-
sary to determine the existence or absence of explosives that
could result in harm to the passengers and aircraft. See id. at
1245.14
  14
    Of course, longstanding precedent allows a screener to call law
enforcement if she inadvertently discovers a possibly contraband item in
the course of performing her safety check, so long as the scope of the
search remains properly cabined to the extent of the lawful administrative
search. $124,570 U.S. Currency, 873 F.2d at 1249 n.7. We have “refuse[d]
to impose an unworkable and unreasonable constraint” on government
agents engaged in good faith administrative searches “by requiring that
they avert their eyes from obvious unlawfulness.” United States v. Seljan,
547 F.3d 993, 1005 (9th Cir. 2008) (en banc) (treating customs official
searches).
10026              UNITED STATES v. MCCARTY
  1.    Import of Search Intent

   On appeal, McCarty contends the district court was correct
in finding that Andrade developed a subjective “impermissi-
ble motive” to search for contraband that extended the war-
rantless search beyond the constitutional bounds of the valid
administrative search, essentially transforming what began as
a lawful administrative search into an independent investiga-
tion for evidence of child pornography. As such, McCarty
argues that Andrade’s subjective motivation was the invali-
dating factor that caused her actions to exceed the scope of
the lawful administrative search. The government counters
that where the overarching search scheme involves only a sin-
gle, constitutionally-valid programmatic motive, the subjec-
tive intentions of the individual agent acting without broad
discretion in carrying out the search are wholly irrelevant.
Accordingly, the government argues, because the TSA agents
here could have viewed any item in McCarty’s bag while
screening for explosives as part of their administrative search
and there was no additional programmatic motive, any subtle
shifts in the individual minds of the TSA screeners had “no
constitutional significance,” the search was not extended
beyond its permissible scope, and all of the items viewed dur-
ing the search should have been admitted.

   In the mine run of Fourth Amendment cases where at least
some quantum of suspicion is involved, the reasonableness
inquiry we conduct is largely an objective one, and the sub-
jective motivations of the individual officer involved are irrel-
evant in determining whether the circumstances objectively
justified the action taken or the intrusion occasioned. See Ash-
croft v. Al-Kidd, 563 U.S. ___, 131 S. Ct. 2074, 2080 (2011).
There are “[t]wo ‘limited exception[s]’ to this rule [for]
special-needs and administrative-search cases, where ‘actual
motivations’ do matter.” Id. (quoting United States v. Knights,
534 U.S. 112, 122 (2001)). In these cases, the special or
administrative need typically dispenses with the Fourth
                      UNITED STATES v. MCCARTY                       10027
Amendment requirement of a warrant or probable cause for
the search. Id. at 2081.

   However, the exemption from the warrant and probable
cause requirements in these types of warrantless, suspicion-
less searches “do[es] not apply where the officer’s purpose is
not to attend to the special needs or to the investigation for
which the administrative inspection is justified.” Id. (citing
Whren v. United States, 517 U.S. 806, 811-12 (1996)).

   [5] Thus, some inquiry into the actual motivations behind
an administrative search is permitted to guard against wholly
pretextual intrusions into the public’s reasonable expectations
of privacy. See Edmond, 531 U.S. at 46-47; United States v.
Hellman, 556 F.2d 442, 444 (9th Cir. 1977) (inventory of
defendant’s car was not validated by administrative search
rationale where department had no standard policy of invento-
rying impounded cars, it was clear that the search was actu-
ally conducted for “an investigatory police motive,” and
officer testified that he instigated the impound specifically to
“justify an investigatory search”); see also Bulacan, 156 F.3d
at 967 (because an “administrative search scheme invests the
Government with the power to intrude into the privacy of
ordinary citizens”—a power with “vast potential for abuse”—
“courts must take care to ensure that an administrative search
is not subverted into a general search for evidence of crime.”
(citations omitted)).15

  [6] Nevertheless, where—as here—the search is “ ‘un-
dertaken pursuant to a general scheme without individualized
suspicion,’ ” Al-Kidd, 131 S. Ct. at 2081 (quoting Edmond,
  15
     Cf. Al-Kidd, 131 S. Ct. at 2082 (describing administrative searches as
“less protective” than searches pursuant to warrants); Whren, 517 U.S. at
811-12 (“the exemption from the need for probable cause (and warrant),
which is accorded to searches made for the purpose of inventory or admin-
istrative regulation, is not accorded to searches that are not made for those
purposes”).
10028             UNITED STATES v. MCCARTY
531 U.S. at 45-46), consideration of the government actor’s
actual motivation has been limited to an inquiry into the pro-
grammatic purposes motivating the search, see Edmond, 531
U.S. at 47; accord Al-Kidd, 131 S. Ct. at 2081. The Supreme
Court has cautioned that this inquiry “is not an invitation to
probe the minds of individual officers acting at the scene.”
Edmond, 531 U.S. at 48 (emphasis added) (citing generally
Whren, 517 U.S. 806).

   Accordingly, this court has held that where a warrantless
search is conducted pursuant to a lawful administrative
scheme with a constitutionally permissible motivation, “the
subjective motive of the individual conducting the search will
not invalidate the search.” See Bulacan, 156 F.3d at 966-67
(citing United States v. Bowhay, 992 F.2d 229, 231 (9th Cir.
1993)). See also United States v. Tsai, 282 F.3d 690, 695-96
(9th Cir. 2002) (applicability of the exception to the probable
cause requirement “turns more on examination of the search’s
scope than on an inquiry into the searcher’s motivation”). In
Bowhay, a police officer searched an arrestee’s bag pursuant
to a standard inventory search policy that required inventory
of all evidence brought to the police station. 992 F.2d at 230.
We held that the fact that the officer had an unlawful second-
ary search purpose in mind when he searched the bag—
hoping to find contraband inside—did not invalidate the oth-
erwise lawful administrative inventory search because the
searching officer’s actions would have been the same regard-
less of his “true” motivation. Id. at 231.

   Similarly, Bulacan examined the effect of an unlawful sec-
ondary purpose—the goal of searching for narcotics—on an
otherwise valid administrative search, where the officers per-
formed administrative searches of all entrants to a federal
building. 156 F.3d at 965. The agents were required, pursuant
to a federal regulation and instruction, to search the bags of
all entrants for both safety hazards and vice items such as nar-
cotics, alcohol, or gambling materials. Id. at 965-66. How-
ever, unlike in Bowhay, the officers had unfettered discretion
                  UNITED STATES v. MCCARTY               10029
in determining which bags or containers to search, based on
their own individual judgment. Id. at 966. We held that, where
the officer had “broad discretion as to the parameters of the
search,” the addition of the programmatic motive to search for
narcotics, which was not legitimately related to the constitu-
tional administrative search for safety purposes, led to the
impermissible extension of the scope of the search, “regard-
less of whether the items searched could have been subject to
a valid administrative search.” Id. at 970.

   Central to Bulacan’s holding was that the search scheme
itself imposed an additional, impermissible motive unrelated
to administrative purposes, such that individual officers, in
exercising the broad discretion granted them, could conduct
more extensive searches based on the secondary law
enforcement-related motive. See id. at 971, 973 (“[W]hen an
administrative search scheme encompasses both a permissible
and an impermissible purpose, and when the officer conduct-
ing the search has broad discretion in carrying out the search,
that search does not meet the Fourth Amendment’s reason-
ableness requirements.”). We were concerned that the second-
ary motive explicit in the search scheme would necessarily
infect the primary search motive, altering the scope of the
search. Id. at 971.

   Likewise, in $124,570 U.S. Currency, we held an airport
search of a passenger’s baggage, pursuant to an established
policy providing a $250 reward for screeners reporting dis-
covery of large sums of U.S. currency, could not be upheld as
a valid administrative search because the policy injected into
the administrative search scheme—at the programmatic level
—an impermissible secondary purpose, and screeners with
broad discretion to decide what bags to search necessarily
could not separate the permissible from the impermissible
motive. 873 F.2d at 1245-47 & n.3; see also id. at 1246 (not-
ing that “the policy of ‘work[ing] hand-in-hand with U.S.
Customs and Port Police regarding the detection and reporting
of drugs and U.S. currency’ will very likely influence [trans-
10030                   UNITED STATES v. MCCARTY
portation security] officers to conduct more searches, and
more intrusive searches, than if they focus on air safety alone”
(first alteration in original)).16

   In determining that Andrade’s subjective intent to search
for child pornography would have invalidated an otherwise
lawful search if the search was one of dual purposes, the dis-
trict court emphasized that Andrade had broad discretion,
similar to the discretion afforded officers in Bulacan, in how
deeply she searched McCarty’s bag. McCarty, 672 F. Supp.
2d at 1098. This was error resulting from conflation of the
applicable law. That the TSA screener here might have had
discretion as broad as the screener in $124,570 U.S. Currency
or Bulacan is immaterial to our analysis because, unlike Bula-
can and $124,570 U.S. Currency, it is undisputed that here
there was no programmatic secondary purpose—Andrade did
not receive any reward for finding contraband, and searching
for evidence of a crime was not part of her assigned duties.
The TSA search scheme under which she operated was
focused solely on the discovery of threats to air travel safety.
Thus, the inquiries into discretion and search intent outlined
in Bulacan and $124,570 U.S. Currency are simply inapplica-
  16
     Although $124,570 U.S. Currency involved an airport search, similar
to this one, in which a bag was flagged as having an unidentifiable dense
mass by an X-ray machine, we did not premise our holding on the subjec-
tive intent of the officer. Rather, we found that the impermissible search
scheme, combined with broad discretion in which containers to search,
invalidated the simultaneous lawful administrative search from the outset.
See 873 F.2d at 1247. We emphasized that
       [n]othing we say today precludes [transportation security] offi-
       cers from reporting information pertaining to criminal activity, as
       would any citizen. We see the matter as materially different
       where the communication is undertaken pursuant to an estab-
       lished relationship, fostered by official policy, even more so
       where the communication is nurtured by payment of monetary
       rewards. The line we draw is a fine one but, we believe, one that
       has constitutional significance.
Id. at 1247 n.7 (emphasis added).
                  UNITED STATES v. MCCARTY                10031
ble here because the “purpose inquiry in [the context of intru-
sions undertaken pursuant to a general scheme without
individualized suspicion] is to be conducted only at the pro-
grammatic level and is not an invitation to probe the minds of
individual officers acting at the scene.” Edmond, 531 U.S. at
45-46.

   Of course, to say that we conduct the Fourth Amendment
inquiry “only at the programmatic level” is not to say that a
lawful administrative search intent, engaged at the inception
of the search but later abandoned, provides carte blanche to
the searching officers to snoop to their hearts’ content without
regard to the scope of their actions. The search must still be
“in furtherance” of the administrative goal, Davis, 482 F.2d
at 908, “no more extensive nor intensive than necessary, in
the light of current technology, to detect the presence of
weapons or explosives[,] . . . [and] confined in good faith to
that purpose,” id. at 913.

   [7] So, as long as (1) the search was undertaken pursuant
to a legitimate administrative search scheme; (2) the search-
er’s actions are cabined to the scope of the permissible admin-
istrative search; and (3) there was no impermissible
programmatic secondary motive for the search, the develop-
ment of a second, subjective motive to verify the presence of
contraband is irrelevant to the Fourth Amendment analysis.
See id.; Edmond, 531 U.S. at 45-46; Aukai, 497 F.3d at 962;
Bulacan, 156 F.3d at 967-68; Bowhay, 992 F.2d at 231. Thus,
the presence here of a secondary desire to confirm that the
items searched might be contraband could not, in and of itself,
invalidate the initially constitutional administrative search
Andrade conducted, at least as long as she actually engaged
in a search for explosives and her actions were no more intru-
sive than necessary to clear the bag of any safety concerns.
See Bowhay, 992 F.2d at 231 (“When the police conduct
would have been the same regardless of the officer’s subjec-
tive state of mind, no purpose is served by attempting to tease
out the officer’s ‘true’ motivation.” (citing Horton v. Califor-
10032             UNITED STATES v. MCCARTY
nia, 496 U.S. 128 (1990))). The subjective intent of the indi-
vidual officer in such a search thus becomes as relevant as
objective conduct only at the point at which the search ceases
legitimately to be for the valid administrative purpose, as that
is the point after which the administrative exception can no
longer justify continuation of the warrantless search.

  2.    Defining Search Scope

   The crux of the issue, then, involves two related questions:
(1) when did Andrade’s administrative search for explosives
truly end, and become a wholly independent search for evi-
dence of child pornography?; and (2) which of Andrade’s
actions exceeded the scope of the administrative search by
becoming “more extensive [or] intensive than necessary, in
the light of current technology, to detect the presence of
weapons or explosives”? Davis, 482 F.2d at 913.

   In a typical case, lines of permissibly cabined and imper-
missibly extended search actions are easy to identify—in
Aukai, for instance, we noted that a TSA screening of airline
passengers and their carry-on luggage was appropriately lim-
ited where TSA screeners escalated the invasiveness of their
search after each level of screening produced a reason to
search more closely. 497 F.3d at 962. We reasoned that taking
such a stairstep approach—first wanding a passenger after a
magnetometer alerted to the presence of metal on the passen-
ger’s body, then asking the passenger to remove items from
his pocket, and ultimately only feeling the outside of the pas-
senger’s pocket after the passenger failed to remove all of the
contents upon request—was both minimally intrusive and
respectful of personal privacy. Each level of increased inva-
siveness in the search was necessary and tailored to dispel the
safety concerns presented. See id.

   [8] By contrast, where an action is taken that cannot serve
the administrative purpose—either because the threat necessi-
tating the administrative search has been dismissed, or
                  UNITED STATES v. MCCARTY                 10033
because the action is simply unrelated to the administrative
goal—the action clearly exceeds the scope of the permissible
search. Cf. United States v. Miles, 247 F.3d 1009, 1014-15
(9th Cir. 2001) (police officer exceeded scope of permissible
Terry frisk where he continued to manipulate a box in a
defendant’s pocket after having concluded that the box could
not possibly be a weapon, as “[h]e had no cause to shake or
manipulate the tiny box on the pretext that he was still look-
ing for a weapon”); United States v. $557,933.89, 287 F.3d
66, 82 (2d Cir. 2002) (suggesting that airport security person-
nel would exceed permissible search scope if they “looked
into areas or opened packages which could not possibly con-
tain weapons or explosives”).

   [9] Here, the scope of the permissible search—mandated
by the TSA protocol—was defined by the point at which the
screener was convinced the bag posed no threat to airline
safety. Once Andrade was sufficiently certain that there were
no explosives or other safety hazards hidden inside McCarty’s
bag, the administrative search was over—nothing else was
required to detect threats to aircraft safety. As the district
court correctly reasoned, any search actions taken thereafter
would impermissibly extend the scope of the search beyond
what was necessary, because they could not possibly meet the
requirement that the screener’s actions be “ ‘strictly tied to
and justified by the circumstances which rendered [the
search’s] initiation permissible.’ ” Davis, 482 F.2d at 911 n.49
(internal quotation marks omitted) (quoting Terry v. Ohio,
392 U.S. 1, 19 (1968)); see also Aukai, 497 F.3d at 962.

   [10] Andrade conceded that, at the point when she read the
content of the letters and looked at the newspaper articles and
advertisements, she was no longer searching for explosives.
Rather, at that point, she had abandoned the search for safety
hazards and was reviewing the items to confirm her feeling
that the photographs were contraband evidencing children in
harm’s way. DCD #57 at 81-85. These actions were indispu-
tably part of an effort to verify the presence of child pornogra-
10034             UNITED STATES v. MCCARTY
phy. Thus, the actions taken in this portion of the search
clearly fell outside the permissible scope of the lawful admin-
istrative search and violated McCarty’s Fourth Amendment
rights because they were more extensive and intrusive than
necessary to detect air travel safety concerns. See Davis, 482
F.2d at 913.

   But the district court found that other portions of Andrade’s
search exceeded the scope of the lawful administrative search
as well. Based on Andrade’s “testimony and lack of credibil-
ity, the court specifically [found] that [she] searched the pho-
tographs in the envelope not for sheet explosives but for
evidence of child pornography.” McCarty, 672 F. Supp. 2d at
1097 n.8. It thus cabined the extent of the lawful search to just
the first few photographs that spilled onto the search table,
and found that the photographs and other items in the enve-
lope had only been discovered as a result of an “overbroad
investigation into the criminal nature of the photographs.” See
id. at 1099.

   We are mindful that factual findings of this type are entitled
to great deference and should be reversed only where a thor-
ough reading of the record leads us to the “definite and firm
conviction that a mistake has been made.” Husain, 316 F.3d
at 835 (internal quotation marks omitted). Nonetheless, we
can find no support in the record for the district court’s con-
clusion that Andrade searched the photographs in the enve-
lope for evidence of child pornography.

   At one point in its decision, the district court asserted that
Andrade had conceded that she was reviewing the contents of
the envelope—including the photographs therein—solely out
of concern for the children depicted. McCarty, 672 F. Supp.
2d at 1094 (referencing DCD #57 at 81-83). It is upon this
statement that the district court based its factual finding that
Andrade was not searching for sheet explosives when she
looked through the photographs in the envelope. Id. at 1097-
98. However, a review of the transcript reveals that Andrade’s
                        UNITED STATES v. MCCARTY                       10035
concession was limited to a statement that when she read lines
from the newspaper clippings and the letters—which occurred
after she had inspected the initially spilled photographs and a
small portion of the photographs in the envelope—her reading
was focused on determining whether the children had been
harmed. DCD #57 at 61-62, 81-82. Andrade did not at any
point state that she had abandoned her primary search for air-
craft safety hazards at the time she viewed the photographs in
the envelope.

   The district court also stated that “Andrade testified that
she went through some of the photographs on the table
because she ‘felt that the children were in a harmful way’ and
‘needed to see more before I called my lead.’ ” McCarty, 672
F. Supp. 2d at 1097 (citing DCD #57 at 61-62). The record
contradicts this conclusion. Although the long question posed
to Andrade before she made those statements did reference
her perusal of the photographs as part of a chronology of her
actions, the part of the question soliciting an answer did not;
it merely asked Andrade “why did you go through those testi-
monies?” DCD #57 at 61-62 (referring to Andrade’s having
read a few lines of the letters).17 Andrade went on to clearly
and repeatedly testify that she viewed the photographs in the
envelope for the purpose of investigating the “possible mas-
  17
    The complete inquiry reads as follows:
       Q: So procedurally I want to go through what happened at that
       point when you decided to go through these items.
          Okay. When you went through the items, you looked at you
       said less than half the photographs, there was these other items
       that you testified to, these ads, newspaper clippings, and letters,
       why did you go through those testimonies?
       A: Because I felt the children were in a harmful way.
       THE COURT: I’m sorry, I did not understand your answer.
       THE WITNESS: I felt that I needed to see more than what I saw
       before I called my lead.
DCD #57 at 61-62.
10036                UNITED STATES v. MCCARTY
sive dark area” on which the CTX machine alarmed, and to
determine if any sheet explosives were hidden therein. See
DCD #57 at 63 (“I needed to go through the envelope itself
because of the possible massive dark area.”); 76 (correcting
defense counsel when he suggested that she began looking
through the materials in the envelope to see what the contents
were about: “Not check exactly what it was. I needed to finish
my check as far as the massive dark area.”); 86 (noting that,
after looking at the photographs that spilled onto the table but
before looking at the newspaper clippings or letter, she “went
into the envelope to see if there was anything hidden in the
envelope”); 89 (noting that she could not determine that there
was no safety concern, with respect to explosives, just by
pulling the photographs out of the envelope; she had to do a
physical search of the items); 95 (correcting defense counsel’s
assertion that at the point she pulled the photographs out of
the envelope, she was no longer concerned with the safety of
the dense mass identified by the scanner: “I still was.”).

   Indeed, defense counsel asked Andrade repeatedly whether
she was still searching for explosives and other safety con-
cerns when she read materials from the envelope, and
Andrade confirmed on each occasion that she was concerned
only about the children in the photos at that point. Id. at 83-
85 (confirming four times that at the time she began to read
the other items in the envelope—including the newspaper
articles and the letters—she was no longer concerned with
safety but needed to know what the nude pictures were
about). However, when defense counsel asserted that Andrade
had searched all of the items in the envelope for the purpose
of determining what the nude photographs were about,
Andrade corrected him, stating “No . . . I need to determine
if there was anything hidden in the pictures — rest of the pic-
tures in the envelope . . . . Because of the massed area. I
needed to continue my search.” Id. at 85.18
  18
    Indeed, the prosecutor objected to defense counsel’s question on this
point as misstating Andrade’s testimony; the district court overruled the
objection. DCD #57 at 85.
                      UNITED STATES v. MCCARTY                       10037
   [11] However unclear Andrade’s testimony was on other
points—exactly which images she saw, how many photo-
graphs spilled onto the table, and whether she touched or did
not touch the photographs on the table before calling the lead
officer—she was consistently clear and emphatic that when
she looked through the photographs in the envelope, she was
still acting to ensure that there were no sheet explosives hid-
den inside. No testimony in the record contradicted hers on
this point. Further, this search intent was consistent with the
TSA protocol requiring Andrade to thumb through the photo-
graphs in order to clear the bag. The district court’s factual
conclusion on this point is without support in the record, and
must be vacated.19

   [12] Thus, the screener’s review of the photographs in the
packet occurred within the scope of the ongoing lawful
administrative search. As a result, her discovery of their
nature coincided with her search for explosives, rather than
followed the formation of an independent and exclusive intent
to search for contraband. Accordingly, Andrade’s viewing of
the photographs from the envelope was justified by and part
of the lawful administrative search, see Aukai, 497 F.3d at
  19
     That the TSA screener did not flip through the entire stack of photo-
graphs before calling her supervisor does not undermine our conclusion.
We find it troubling that the district court treated the fact that the search
was not completed as a strong indicator that Andrade’s testimony was not
credible. See McCarty, 672 F. Supp. 2d at 1098. A review of the testimony
presented shows that only a few short minutes passed between the time the
CTX machine alarmed on the bag and the time law enforcement was cal-
led, DCD #57 at 201, and the TSA lead officer was already in the room
when Andrade began the lawful search. Given the timeframe within which
the events occurred, we are unsurprised that the TSA screener did not
complete the thumb through before her lead came over to see what possi-
ble contraband had been found, and we think this fact should not subvert
the notion that a complete—or at least further—protocol search would
have been required to dispel any safety concerns after viewing the initial
photographs. Supporting our reasoning is the fact that although Andrade
did not finish clearing the bag of safety concerns herself before calling the
lead, TSA Supervisor Kamohai did so. Id. at 95.
10038             UNITED STATES v. MCCARTY
962, and—as we clarified above—even the development of a
secondary desire to confirm that the photographs evidenced
contraband did not invalidate that search, see Bowhay, 992
F.2d at 231.

B.   Probable Cause and Suppression

   After reaching its conclusion that Andrade’s search of the
photographs quickly went beyond the bounds of a proper
administrative search, the district court considered whether
the photographs lawfully seen by the screeners provided prob-
able cause to arrest McCarty. It answered that question by
attempting to determine whether the lawfully-viewed photo-
graphs constituted child pornography. This approach was
erroneous.

   [13] To show that the police had probable cause to arrest
McCarty, the government is required to prove only that “ ‘at
the moment of arrest the facts and circumstances within the
knowledge of the arresting officers and of which they had rea-
sonably trustworthy information were sufficient to warrant a
prudent man in believing that the petitioner had committed or
was committing an offense.’ ” United States v. Jensen, 425
F.3d 698, 704 (9th Cir. 2005) (quoting United States v. Ber-
nard, 623 F.2d 551, 559 (9th Cir. 1980)). Under this objective
standard, the government need not “show[ ] that the
officer[s’] belief is more likely true than false,” United States
v. Brobst, 558 F.3d 982, 997 (9th Cir. 2009), and need not
demonstrate “probable cause for every element of the
offense,” Blankenhorn v. City of Orange, 485 F.3d 463, 472
(9th Cir. 2007) (internal quotation marks omitted). Instead,
the government must show that the officers had an objectively
reasonable belief that McCarty committed a crime, based on
the totality of the relevant circumstances. See Luchtel v.
Hagemann, 623 F.3d 975, 979 (9th Cir. 2010). Accordingly,
the government is not required to prove that all or any of the
                      UNITED STATES v. MCCARTY                       10039
photographs actually exhibited child pornography in order to
establish probable cause for McCarty’s arrest.20

   [14] On remand, the district court’s probable cause deter-
mination should proceed in two steps. First, the court should
decide what materials may be considered in determining
whether probable cause existed to arrest McCarty. As Jensen
illustrates, courts generally consider the information known to
the arresting officers at the time of the arrest. Here, Serrao
testified that he had viewed all of the photographs in McCar-
ty’s envelope and perhaps also some of the textual materials
before making the arrest.

   The general rule must, however, be narrowed here, because
the fruits of an unlawful search cannot provide probable cause
for an arrest, see Johnson v. United States, 333 U.S. 10, 16-17
(1948), and it is clear some portion of this search was unlaw-
ful. Although—consistent with our enumeration of the
search’s lawful scope—all of the photographs viewed by the
screeners as part of the lawful search for explosives must be
considered in reaching a probable cause determination, the
textual materials seen by the screeners may only be consid-
ered if the government demonstrates that suppression is an
inappropriate remedy. Similarly, the photographs not viewed
by the screeners may be considered only if they do not consti-
   20
      Cf. United States v. Hill, 459 F.3d 966, 972-73 & n.9 (9th Cir. 2006)
(while a single photo of a naked child in a bathtub would not suffice to
establish probable cause for a search warrant, a detailed description of two
photographs of semi-nude girls revealing their breasts and pubic areas,
which could have been meant to “ ‘arouse or satisfy the sexual cravings
of a voyeur,’ ” produced probable cause to believe that evidence of child
pornography would be found on the defendant’s computer, even if the
defendant could negate their contraband nature at trial (quoting United
States v. Wiegand, 812 F.2d 1239, 1244 (9th Cir. 1987))); United States
v. Moore, 215 F.3d 681, 686-87 (7th Cir. 2000) (finding that photos of
nude children, including some depicting nude boys in nature scenes that
were not necessarily sexually suggestive and some depicting nude girls in
sexually suggestive poses, produced probable cause to effect a warrantless
arrest for possession of child pornography).
10040                UNITED STATES v. MCCARTY
tute fruit of the poisonous tree. See, e.g., United States v.
Davis, 332 F.3d 1163, 1171 (9th Cir. 2003) (listing the inde-
pendent source, inevitable discovery, and attenuated basis
exceptions to the rule that evidence discovered as a result of
an illegal search must be excluded).21

  Once the district court determines which evidence may be
considered as part of the probable cause determination, it
must determine whether that evidence was “sufficient to war-
rant a prudent man in believing that the petitioner had com-
mitted or was committing an offense.” Jensen, 425 F.3d at
704. Again, we stress that, to meet this standard, the govern-
ment does not need to prove that the arresting officers knew
McCarty had committed a crime, but only that the officers’
belief that McCarty committed crimes related to child pornog-
raphy was an objectively reasonable one.

  [15] Finally, the district court held that suppression was an
appropriate remedy for the screeners’ overbroad search.
Because this conclusion rested on the district court’s errone-
ous finding that the screeners searched McCarty’s photo-
graphs for evidence of child pornography, we vacate this
holding and remand for the district court to reconsider
whether suppression is appropriate in light of our conclusions
here.
  21
     Although the government raised an inevitable discovery-type theory
in its opposition to McCarty’s motions to suppress all evidence, see DCD
#61 at 12-13 (contending that the TSA officers would inevitably have dis-
covered the entire contents of the envelope, including all of the photo-
graphs, had they not stopped the administrative search before completion
in order to call law enforcement), the district court did not consider this
theory in its order granting McCarty’s motion to suppress. We express no
opinion as to the merits of this argument, but note that the district court
may wish to consider it on remand.
                  UNITED STATES v. MCCARTY                10041
                         CONCLUSION

   The order suppressing the evidence obtained as a result of
the airport screening and the follow-on consent- and warrant-
based searches of McCarty’s computer and other materials is
vacated, and the case remanded to the district court for further
proceedings consistent with this Opinion.

  VACATED and REMANDED.
