FILED
                                                                      United States Court of Appeals
                                       PUBLISH                                Tenth Circuit

                      UNITED STATES COURT OF APPEALS                        August 17, 2017

                                                                          Elisabeth A. Shumaker
                             FOR THE TENTH CIRCUIT                            Clerk of Court
                         _________________________________

UNITED STATES OF AMERICA,

      Plaintiff - Appellee,

v.                                                          No. 16-3292

STEPHEN M. NELSON,

      Defendant - Appellant.
                      _________________________________

                     Appeal from the United States District Court
                              for the District of Kansas
                          (D.C. No. 2:15-CR-20080-JAR-1)
                       _________________________________

Daniel T. Hansmeier, Appellate Chief (Melody Brannon, Federal Public Defender, and
Tim Burdick, Assistant Federal Public Defender, with him on the briefs), Office of the
Federal Public Defender, Kansas City, Kansas, for Defendant-Appellant.

James T. Ward, Special Assistant United States Attorney (Thomas E. Beall, United States
Attorney, with him on the brief), Office of the United States Attorney, Kansas City,
Kansas, for Plaintiff-Appellee.
                        _________________________________

Before TYMKOVICH, Chief Judge, MATHESON and MORITZ, Circuit Judges.
                 _________________________________

MORITZ, Circuit Judge.
                    _________________________________

      After seven law enforcement officers arrested Stephen Nelson in a private

residence, one officer continued searching the residence and found two firearms. The

government attributed the firearms to Nelson, and he was indicted for possession of a
firearm by a felon. See 18 U.S.C. § 922(g)(1). Nelson moved to suppress the

firearms, arguing that the officers violated the Fourth Amendment by continuing to

search the residence after arresting him. The district court denied Nelson’s motion,

concluding that the post-arrest search was a valid protective sweep because the

officers “could have reasonably believed that someone other than [Nelson] was

hiding in the house.” R. vol. 1, 95.

      Nelson entered a conditional guilty plea, and he now appeals the district

court’s order denying his suppression motion. We vacate the denial based on our

conclusion that the searching officer had no basis to reasonably believe that an

unknown, dangerous person was hiding in the residence. Nevertheless, we remand for

the district court to determine, in the first instance, whether the owner of the

residence consented to the search.

                                            I

      While Nelson was serving a term of supervised release, his probation officer

obtained an arrest warrant based on Nelson’s alleged failure to comply with several

conditions of that release. Although the probation officer indicated that Nelson’s

whereabouts were unknown, the United States Marshals Service learned that Nelson

occasionally stayed at a house owned by Antonio Bradley. Nelson had a small child

with Bradley’s daughter, Allie, who lived with her parents.1 Deputy Marshal Jovan

Archuleta asked Bradley to contact him if Nelson appeared at the Bradley residence.


      1
       To avoid confusion, we refer to Antonio Bradley as “Bradley” and to Allie
Bradley as “Allie.”

                                            2
      Bradley did exactly that. On May 2, 2015, he told Archuleta that Nelson was

in the Bradley residence and that the deputy marshals could “go inside and search

for” Nelson. R. vol. 2, 36. Three deputy marshals—Chris Johnson, Bradley Owens,

and Michael Thibault (collectively, the deputies)—formed a task force to execute the

arrest warrant with four Kansas City, Kansas police officers. The deputies drove to

the Bradley residence and knocked and announced at the front door.

      After a minute or so of knocking, Allie opened the door. When the deputies

informed Allie of their intent to arrest Nelson, she responded that he was upstairs.

Allie said that she would retrieve Nelson herself and then attempted to shut the door

on the deputies. But Johnson prevented Allie from doing so, and the deputies entered

the residence.

      The Bradley residence has four levels. The deputies entered at the third level,

which consists of a living room, a dining room, and a kitchen. The fourth level,

where Allie asserted Nelson was located, contains three bedrooms. The second level

consists of a family room and a garage. From there, a set of stairs descends into a

subbasement area—the first level.

      Upon entry, the deputies cleared the third level. The deputies then shouted

upstairs, instructing Nelson to show himself. Meanwhile, Thibault and Owens

escorted Allie to the second level so that she could retrieve her child. After clearing

that level, Thibault and Owens moved to the top of the stairs leading down to the first

level. That’s when Thibault saw movement on the first level.




                                            3
      From the top of the stairs, Thibault shouted commands for the unidentified

person to come out and show his hands. After ten seconds of shouting, Nelson came

around the corner with his hands in the air. Thibault and Owens instructed Nelson to

walk up the stairs to the second level and placed him in custody there. Owens then

descended the stairs to search the first level. There, he found two firearms underneath

a pile of clothes on a bed. Each of the Bradleys disavowed knowledge and ownership

of the firearms.

      Because Nelson had two previous felony convictions, the government charged

him with possession of a firearm by a felon. Nelson moved to suppress the firearms,

arguing that the deputies violated the Fourth Amendment by continuing to search the

residence after arresting him. In response, the government made two arguments

relevant on appeal: (1) Bradley, the owner of the residence, consented to the search;

and (2) Owens lawfully searched the first level under the protective-sweep doctrine

set forth in Maryland v. Buie, 

(1990).

      In Buie, the Court recognized two exceptions to the general rule that police

must obtain a warrant to search a home. Under the first exception (Prong One) the

police may, in conjunction with an arrest in a home, “as a precautionary matter and

without probable cause or reasonable suspicion, look in closets and other spaces

immediately adjoining the place of arrest from which an attack could be immediately

launched.” 

Under the second exception (Prong Two), police may conduct

a “protective sweep” beyond areas immediately adjoining the arrest if there are

“articulable facts which, taken together with the rational inferences from those facts,


                                           4
would warrant a reasonably prudent officer in believing that the area to be swept

harbors an individual posing a danger to those on the arrest scene.” 

       Citing Prong Two, the district court concluded that the facts surrounding

Nelson’s arrest “would support a reasonable belief that someone else was in the

house who could pose a danger to the [deputies] or others.” R. vol. 1, 94. Thus, the

district court concluded that Owens conducted a valid protective sweep and denied

Nelson’s motion to suppress on that basis. Nelson appeals.

                                            II

       On appeal, Nelson argues that the district court erred in relying on Prong Two

to deny his motion because the deputies had no reason to believe that a dangerous

third person was hiding in the residence. The government defends the district court’s

reasoning and asserts three alternative grounds for affirming: (1) under Prong One,

the deputies lawfully searched the first level because that area immediately adjoins

the place of Nelson’s arrest; (2) the good-faith exception to the exclusionary rule

applies; and (3) Bradley consented to a search of the entire residence. In reviewing

these arguments and the district court’s denial of Nelson’s motion, we examine the

district court’s factual findings for clear error and its application of the relevant legal

standards de novo. See United States v. Hauk, 

, 1185 (10th Cir. 2005).

                                             A

       The district court concluded that Deputy Owens lawfully conducted a

protective sweep of the first level because, under Prong Two, the deputies could have




                                             5
reasonably believed that “someone else [aside from Nelson] was in the house who

could pose a danger to the [deputies] or others.” R. vol. 1, 94. We disagree.

      The district court relied on three facts in reaching its conclusion: (1) Allie

attempted to shut the front door on the deputies; (2) Allie incorrectly informed the

deputies that Nelson was upstairs, on the fourth level, when in fact he was on the first

level; and (3) Nelson failed to immediately show himself to the deputies when they

instructed him to do so. But these facts don’t create an inference that someone other

than Nelson was hiding in the house, whether the three facts are taken separately or

together.

      Nor does the government explain how these facts create the necessary

inference. Instead, the government resorts to a fallback position—that “the officers

had no way of knowing if anyone else was in the residence.” Aplee. Br. 29. But for

the following reasons, that argument turns Prong Two on its head.

      Under Prong Two, the government is required to articulate specific facts

giving rise to the inference of a dangerous third person’s presence. 

. As we’ve previously explained, “there could always be a dangerous person

concealed within a structure. But that in itself cannot justify a protective sweep,

unless such sweeps are simply to be permitted as a matter of course . . . .” United

States v. Carter, 

, 1242-43 (10th Cir. 2004); see United States v. Roof,

103 F. App’x 652, 658 (10th Cir. 2004) (unpublished) (“A mere absence of

information about whether anyone remains in a home does not justify a protective

sweep.”). In short, “‘[n]o information’ cannot be an articulable basis for a sweep that


                                            6
requires information to justify it in the first place.” United States v. Colbert, 

, 778 (6th Cir. 1996). Accordingly, if the deputies had no knowledge regarding

the potential presence of a third person, then the government is per se unable to make

the affirmative showing that Buie requires.

       Our prior decisions in this area illustrate the type of specific, articulable facts

that might reasonably suggest the presence of an unknown, dangerous person. See,

e.g., United States v. Denson, 

, 1219-20 (10th Cir. 2014) (affirming

validity of Prong Two protective sweep based on specific information that “a second

person lived in the home who was wanted on an outstanding warrant”); 

(concluding that police “had a reason to suspect that there was an

unidentified person lurking somewhere in the house” because while police were

waiting outside house, third party drove up and appeared to enter house); United

States v. Cavely, 

, 994 (10th Cir. 2003) (“When [arresting officers]

asked if anyone else was in the house, [arrestee] told them he had ‘a friend’ inside.”).

In contrast with the facts in those cases, the three facts the district court identified

here are self-evidently insufficient under Buie.

       The government, perhaps recognizing as much, asserts that two additional

facts support the inference that a dangerous third person was hiding in the residence.

First, the government points to the district court’s statement that “Thibault noticed

shadows moving at the bottom of the stairs in the [first level].” R. vol. 1, 89. But we

decline to address this argument because the government’s brief entirely fails to

explain the significance of this putative fact. See Bronson v. Swensen, 

,


                                             7
1105 (10th Cir. 2007) (explaining that “cursory statements, without supporting

analysis and case law, fail to constitute the kind of briefing that is necessary to avoid

application of the [waiver] doctrine”).

       The government asserts that a second additional fact supports this inference:

Allie informed the deputies that her cousin was in the house. That’s precisely the sort

of specific, articulable information that might have permitted Owens to search the

first level after arresting Nelson. For that information to be relevant, of course,

Owens had to have it before he conducted the protective sweep. But as the

government acknowledges, the district court expressly declined to decide “whether

the [deputies] learned about the cousin before they performed the search of the [first

level].”2 R. vol. 1, 95 n.19.

       Because this question of timing is material, we would ordinarily remand for

the district court to make a factual finding. See United States v. Ramstad, 

, 1265 (2000). But here, the government has conceded—both below and on

appeal—that Owens didn’t “find out” about Allie’s cousin until after he searched the




       2
         The district court stated that the chronology of Allie’s statements about her
cousin was “unclear.” R. vol. 1, 95 n.19. But the court’s own recitation of facts seems
to clearly indicate that Allie told the deputies about her cousin after Nelson’s arrest
and, at the earliest, contemporaneously with Owens’ protective sweep. According to
the district court, “Johnson patted [Nelson] down for weapons, but found none. Allie
then explained to Johnson and Thibault that her sixteen-year-old cousin was also in
the house . . . . Meanwhile, Owens entered the subbasement and began searching for
other people who could pose a potential threat to the officers.” 

(emphases
added).

                                            8
first level.3 Aplee. Br. 6. Accordingly, the government has conceded any argument

that Owens’ knowledge of the cousin’s potential presence justified the protective

sweep. See Guidry v. Sheet Metal Workers Int’l Ass’n, Local No. 9, 

, 716

(10th Cir. 1993) (noting that statements in briefs and at oral argument may, in court’s

discretion, operate as judicial admissions that “have the effect of withdrawing a fact

from issue and dispensing wholly with the need for proof of the fact” (quoting Am.

Title Ins. Co. v. Lacelaw Corp., 

, 226 (9th Cir. 1988))), rev’d in part on

reh’g sub nom. Guidry v. Sheet Metal Workers Nat’l Pension Fund, 

(10th Cir. 1994) (en banc).

      Because neither the district court’s three facts nor the government’s two

additional facts permitted Owens to infer that a dangerous third person was hiding in

the Bradley residence, the first-level search was not a valid protective sweep under

Prong Two.

                                           B

      The government argues that we may nevertheless affirm the district court’s

denial of Nelson’s suppression motion on an alternative ground: Prong One. In

conjunction with an arrest in a home, the police may, “as a precautionary matter and

without probable cause or reasonable suspicion, look in closets and other spaces


      3
        After making this same concession at oral argument, the government insisted
that Johnson’s pre-search knowledge of the cousin’s potential presence was imputed
to Owens through the collective-knowledge doctrine. As Nelson points out, that
doctrine would apply only if Johnson instructed Owens to conduct the protective
sweep. See United States v. Chavez, 

, 1345 (10th Cir. 2008). There’s
no evidence of any such instruction.

                                           9
immediately adjoining the place of arrest from which an attack could be immediately

launched.” 

. The government asserts that Prong One validates

the first-level search under two theories: (1) the deputies arrested Nelson on the first

level, so the search of the bed on that level occurred immediately adjacent to the

arrest; and (2) even if the deputies arrested Nelson on the second level, the first level

nevertheless immediately adjoins the second level. But the government concedes that

it failed to make these specific arguments below. And Nelson argues that we should

decline to consider them on that basis.4

      We generally don’t “address arguments presented for the first time on appeal.”

United States v. Mora, 

, 1216 (10th Cir. 2002). Nevertheless, the

government correctly notes that we have discretion to affirm on alternative grounds

“when the record below is sufficient to permit us to conclude, as a matter of law, that

[d]efendant’s Fourth Amendment rights were not violated.” United States v. Mosley,

, 1324 n.2 (10th Cir. 2014). But the record lacks the necessary factual

findings for us to do so here. In particular, the district court made no findings

regarding the proximity of the location of Nelson’s arrest to the area that Owens


      4
         The government asserted at oral argument that its Prong One arguments are
functionally similar to its argument below that Owens’ sweep was a valid search
incident to Nelson’s arrest. But to the extent the government intended to suggest that
the latter argument preserved the former for appeal, we disagree; our general rule
against considering new arguments on appeal applies equally when “a litigant
changes to a new theory on appeal that falls under the same general category as an
argument presented at trial.” Lyons v. Jefferson Bank & Tr., 

, 722 (10th
Cir. 1993). Moreover, because the government failed to raise this point before oral
argument, we deem it waived. See Ross v. Univ. of Tulsa, 

, 1292 n.10
(10th Cir. 2017).

                                           10
ultimately searched. We therefore decline to consider the government’s Prong One

arguments. See Brown v. Perez, 

, 1237 (10th Cir. 2016) (declining to

consider newly raised argument that “turn[ed] in substantial part on a question of

fact”).

                                              C

          Next, the government urges us to affirm the district court’s order under the

good-faith exception to the exclusionary rule. See United States v. Herrera, 

, 1249 (10th Cir. 2006) (explaining that suppression isn’t appropriate when

officer relies in good-faith on a third party’s mistake). Specifically, the government

argues that Owens’ search “was close enough to the line of validity that an

objectively reasonable officer would have acted” in the same way. Aplee. Br. 39.

          But again, the government concedes that it failed to raise this argument below.

And we decline to consider it because the record lacks factual development on key

issues. See 

. For instance, Nelson argues that we should

decline to apply the good-faith exception here because the deputies acted pursuant to

“a general policy of indiscriminate and unconstitutional protective sweeps during in-

home arrests.” Aplt. Br. 23. But the scope of that policy isn’t entirely clear from the

deputies’ testimony. In particular, we can’t be certain whether it calls for post-arrest

protective sweeps for potential third parties. And the district court made no such

findings.5


          5
       Thibault, the Marshals’ supervisor in Kansas City, Kansas, testified without
prompting at the suppression hearing, “Once we make entrance into the residence,

                                             11
       In any event, even if we considered the government’s new argument, we would

reject it on the merits. We’ve previously explained that the Supreme Court has

“limited [the good-faith] exception to circumstances where someone other than a

police officer has made the mistaken determination that resulted in the Fourth

Amendment violation.” 

. Because the government neither

suggests that the deputies relied on a third party’s mistake—a wrongly issued search

warrant, for instance—in deciding to search the first level, nor explains why this case

might present the “very unusual circumstances” that would convince us to “extend

th[e] good-faith exception beyond its pedigree,” 

we decline to affirm on

this basis.

                                           D

       Finally, the government argues that we should affirm the district court’s order

because Bradley consented to a search of his entire residence. Nelson, in contrast,

argues that the deputies reached the limit of Bradley’s consent when they found and

arrested Nelson. The district court expressly declined to decide this issue.

       There’s no dispute that Bradley authorized the deputies to enter his residence

in order to arrest Nelson. The question is whether Bradley’s limited consent extended

we’re going to check everywhere that a body could be.” R. vol. 2, 80. And he
testified that this is a “blanket safety rule” that applies “on any occasion in which
[he] mak[es] an arrest” in a residence. 

We note that if, as Nelson suggests,
the United States Marshals Service for the District of Kansas maintains a practice
that systemically ignores the framework set forth in Buie, such a practice would be
troubling. As we explained in another case concerning law-enforcement officials in
the Kansas City area, “The Fourth Amendment does not sanction automatic searches
of an arrestee’s home, nor does the fact-intensive question of reasonable suspicion
accommodate a policy of automatic protective sweeps.” 

.

                                           12
beyond that purpose, authorizing the deputies to indiscriminately search the residence

after the arrest. Bradley testified about the scope of his consent as follows:

       Q. Okay. So you gave the U.S. marshals permission to go inside your
       house?

       A. Uh-huh.

       Q. And did you give the U.S. marshals permission to go in there and
       search for him and try to find him?

       A. Yeah. I told them they can go find him. He’s in my house.

R. vol. 2, 17.

       This testimony suggests that Bradley consented for the deputies to search his

house only to the extent necessary to find and arrest Nelson. With some prompting,

however, Bradley agreed that the scope of his consent “included anything that [the

deputies] needed to reasonably do to safely arrest” Nelson. 

But Bradley

never stated whether that license extended beyond the time of Nelson’s arrest.

       We won’t decide this issue in the first instance on appeal. “Whether a search

remains within the boundaries of the consent is a question of fact to be determined

from the totality of the circumstances, and a trial court’s findings will be upheld

unless they are clearly erroneous.” United States v. Pena, 

, 1514 (10th

Cir. 1990). Although the government raised this argument below—unlike its Prong

One and good-faith arguments—the district court declined to conduct the fact finding

necessary for us to resolve this issue on appeal. We therefore remand for it to do so.

.




                                           13
                                    *      *      *

      We vacate the district court’s order denying Nelson’s motion to suppress and

remand for the district court to determine, on the basis of the evidence already in the

record, whether the deputies exceeded the scope of Bradley’s consent when they

continued searching his residence after they arrested Nelson.




                                          14