PUBLISH UNITED STATES COURT OF APPEALS FOR THE TENTH CIRCUIT

________________ _________________ UNITED STATES OF AMERICA, Plaintiff - Appellee,

v. STEPHEN M. NELSON, Defendant - Appellant. No. 16-3292

________________ _________________ 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 (M elody Brannon, Federal Public Defender, and Tim Burdick, Assistant Federal Public Defend er, with him on the briefs), Office of the Federal Public Defender, Kansas C ity, 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 con tinued searching the residen ce and found two firearms. The government attributed the firearms to Nels on, and he was indicted for possession of a FILED United States Court of Appeals Tenth Circuit 

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Elisabeth A. Shumaker Clerk of Court2 firearm by a felon. See 18 U.S.C. § 922(g)(1). Nels on moved to suppress the firearms, arguing that the o fficers violated the Fourth Amendment by continuing to search the residence after ar resting him. The district c ourt denied Nelson’s motion, concluding that the post-arre st search was a valid pr otective sweep because the officers “could have reasona bly 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 suppr ession motion. We vacate the denial based on our conclusion that the searching officer had no basis to reasonably believe that an unknown, dangerous pe rson 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 supe rvised release, his probation officer obtained an arrest warrant ba sed 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 An tonio Bradley. Nelson had a small child with Bradley’s daughter, Allie, who lived with her parents. 1 Deputy Marshal Jovan Archuleta asked Bradley to c ontact 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.”3 Bradley did exactly that. On May 2, 20 15, he told Archuleta that Nelson was in the Bradley residence and that the deputy marshals c ould “go inside and search for” Nelson. R. vol. 2, 36. Three deput y marshals—Chris J ohnson, Bradley Owens, and Michael Thibault (collectively, the depu ties)—formed a task fo rce to execute the arrest warrant with four Ka nsas City, Kansas police offi cers. The deputies drove to the Bradley residence and knocked a nd announced at the front door. After a minute or so of knocking, A llie opened the door. When the deputies informed Allie of th eir intent to arrest Nelson, sh e responded that he was upstairs. Allie said that she would retrieve Nelson he rself and then attemp ted to shut the door on the deputies. But Johnson prevented A llie from doing so, and the deputies entered the residence. The Bradley residence has four levels. The deputies en tered at the third level, which consists of a living room, a dining room, and a k itchen. The fourth level, where Allie asserted Nelson was located, contains thr ee 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 re trieve 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.4 From the top of the stairs, Thibault shouted commands for the unidentified person to come out and show his hands. Af ter 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 a nd 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 kn owledge and ownership of the firearms. Because Nelson had two previous fel ony 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 Four th Amendment by continuing to search the residence after arresting hi m. In response, the govern ment made two arguments relevant on appeal: (1) Bradle y, the owner of the residen ce, consented to the search; and (2) Owens lawfully searched the firs t level under the protective-sweep doctrine set forth in Maryland v. Buie , 494 U.S. 325 (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 susp icion, look in closets and other spaces immediately adjoining the place of arrest from which an attack could be immediately launched.” Id . at 334. Under the second excepti on (Prong Two), police may conduct a “protective sweep” beyond areas immediately adjoini ng the arrest if there are “articulable facts which, taken together with the rational inferen ces from those facts,5 would warrant a reasonably prudent officer in believing that the area to be swept harbors an individual posing a dange r to those on the arrest scene.” Id . at 335. Citing Prong Two, the district cour t concluded that the facts surrounding Nelson’s arrest “would suppor t a reasonable belief that someone else was in the house who could pose a danger to the [deputie s] or others.” R. vol. 1, 94. Thus, the district court concluded th at Owens conducted a valid pr otective sweep and denied Nelson’s motion to suppress on th at basis. Nelson appeals.
II On appeal, Nelson argues that the distri ct court erred in relying on Prong Two to deny his motion because the deputies ha d no reason to believe that a dangerous third person was hiding in the residence. Th e government defends the district court’s reasoning and asserts three alternative gr ounds 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 sear ch of the entire resi dence. In reviewing these arguments and the district court’s de nial of Nelson’s motion, we examine the district court’s factua l findings for clear error and its a pplication of the relevant legal standards de novo. See United States v. Hauk , 412 F.3d 1179, 1185 (10th Cir. 2005). A The district court concluded that Deputy Owens lawfully conducted a protective sweep of the first level because, under Prong Tw o, the deputies could have6 reasonably believed that “som eone else [aside from Ne lson] 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 fact s in reaching its c onclusion: (1) Allie attempted to shut the front door on the de puties; (2) Allie inco rrectly 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 govern ment 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 argumen t turns Prong Two on its head. Under Prong Two, the government is required to articul ate specific facts giving rise to the inference of a dangerous third person’s presence. See 494 U.S. at 337. As we’ve previously explained, “t here 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 perm itted as a matter of course . . . .” United
States v. Carter , 360 F.3d 1235, 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 that7 requires information to jus tify it in the first place.” United States v. Colbert , 76 F.3d 773, 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 illustrat e the type of specifi c, articulable facts that might reasonably sugge st the presence of an un known, dangerous person. See,

e.g. , United States v. Denson , 775 F.3d 1214, 1219-20 (10th Cir. 2014) (affirming validity of Prong Two protective sweep ba sed on specific information that “a second person lived in the home who was wa nted on an outstanding warrant”); Hauk , 412 F.3d at 1192 (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, thir d party drove up and appeared to enter house); United States v. Cavely , 318 F.3d 987, 99 4 (10th Cir. 2003) (“When [arresting officers] asked if anyone else was in th e 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-evident ly insufficient under Buie

. The government, perhaps recognizing as much, asserts th at two additional facts support the inference th at a dangerous third person wa s hiding in the residence. First, the government points to the district court’s statement th at “Thibault noticed shadows moving at the bottom of the stairs in the [first level].” R. vol. 1, 89. But we decline to address this ar gument because the government’s brief entirely fails to explain the significance of this putative fact. See Bronson v. Swensen , 500 F.3d 1099,8 1105 (10th Cir. 2007) (explaining that “cu rsory statements, without supporting analysis and case law, fail to constitute the kind of briefi ng that is necessary to avoid application of the [waiver] doctrine”). The government asserts that a second additional fact s upports this inference: Allie informed the depu ties that her cousin was in the ho use. That’s precisely the sort of specific, articulable information that might have permitted Owens to search the first level after arresting Ne lson. 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 th e 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 w ould ordinarily remand for the district court to make a factual finding. See United States v. Ramstad , 219 F.3d 1263, 1265 (2000). But he re, the government has c onceded—both below and on appeal—that Owens didn’t “fi nd out” about Allie’s cousin until after he searched the

2 The district court stated that the chronology of A llie’s statements about her cousin was “unclear.” R. vol. 1, 95 n.19. Bu t the court’s own recitation of facts seems to clearly indicate that Alli e told the deputies about her cousin after Nelson’s arrest and, at the earliest, cont emporaneously with Owens’ pr otective sweep. According to the district court, “Johnson patted [Nels on] down for weapons, but found none. Allie then explained to Johnson and Thibault that her sixteen-year-old c ousin was also in the house . . . . Meanwhile , Owens entered the subbasem ent and began searching for other people who could pose a poten tial threat to the officers.” Id. at 89-90 (emphases added).9 first level. 3 Aplee. Br. 6. Accordingly, the government has conceded any argument that Owens’ knowledge of the cousin’s pot ential presence justified the protective
sweep. See Guidry v. Sheet Metal Wor kers Int’l Ass’n, Local No. 9 , 10 F.3d 700, 716 (10th Cir. 1993) (noting that st atements in briefs and at or al argument may, in court’s discretion, operate as judicial admissions that “have the e ffect of withdrawing a fact from issue and dispensing who lly with the need for pr oof of the fact” (quoting Am. Title Ins. Co. v. Lacelaw Corp. , 861 F.2d 224, 226 (9th Cir. 1988))), rev’d in part on reh’g sub nom. Guidry v. Sheet Metal Workers Nat’l Pension Fund , 39 F.3d 1078 (10th Cir. 1994) (en banc). Because neither the distri ct court’s three facts nor the government’s two additional facts permitted Owens to infer th at 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 affi rm the district court’s denial of Nelson’s suppre ssion motion on an alternativ e ground: Prong One. In conjunction with an arrest in a home, the police may, “as a prec autionary matter and without probable cause or reasonable susp icion, 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 colle ctive-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 , 534 F.3d 1338, 1345 (10th Cir. 2008). There’s no evidence of any such instruction.10 immediately adjoining the place of arrest from which an attack could be immediately launched.” Buie , 494 U.S. at 334. The government as serts 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 immedi ately 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 governme nt concedes that it failed to make these sp ecific arguments below. And Nelson argues that we should decline to consider them on that basis. 4 We generally don’t “address arguments pr esented for the first time on appeal.” United States v. Mora , 293 F.3d 1213, 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 Amendmen t rights were not violated.” United States v. Mosley , 743 F.3d 1317, 1324 n.2 (10th Cir. 2014)

. But the record lacks the necessary factual findings for us to do so here. In partic ular, the district c ourt made no findings regarding the proximity of the location of Nelson’s arrest to the area that Owens

4 The government asserted at oral ar gument that its Pro ng One arguments are functionally similar to its argument belo w that Owens’ sweep was a valid search incident to Nelson’s arrest. But to the extent the governme nt intended to suggest that the latter argument preserved the former fo r appeal, we disagree; our general rule against considering new ar guments on appeal applies equally when “a litigant changes to a new theory on appeal that fa lls under the same general category as an argument presented at trial.” Lyons v. Jefferson Bank & Tr. , 994 F.2d 716, 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 , 859 F.3d 1280, 1292 n.10 (10th Cir. 2017).11 ultimately searched. We ther efore decline to consider the government’s Prong One arguments. See Brown v. Perez , 835 F.3d 1223, 1237 (10th Cir. 2016) (declining to consider newly raised argumen t that “turn[ed] in substa ntial part on a question of fact”). C Next, the government urges us to affirm the district cour t’s order under the good-faith exception to th e exclusionary rule. See United States v. Herrera , 444 F.3d 1238, 1249 (10th Cir. 2006) (explaining that suppr ession isn’t appropriate when officer relies in good-faith on a third party’s mistake) . Specifically, the government argues that Owens’ search “was close e nough to the line of validity that an objectively reasonable officer would have act ed” 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 th e record lacks factual development on key issues. See Brown , 835 F.3d at 1237. For instance , Nelson argues th at we should decline to apply the good-fa ith exception here because th e deputies acted pursuant to “a general policy of indiscri minate and unconstitutional protective sweeps during inhome arrests.” Aplt. Br. 23. But the scope of that policy isn’t en tirely clear from the deputies’ testimony. In particular, we can’t be certain wh ether it calls for post -arrest protective sweeps for potential third parties. And the dist rict court made no such findings. 5

5 Thibault, the Marshals’ supervisor in Kansas City, Kansas, testified without prompting at the suppression hearing, “On ce we make entrance in to the residence,12 In any event, even if we considered the government’ s new argument, we would reject it on the merits. We’v e previously explained that the Supreme Court has “limited [the good-faith] exception to ci rcumstances where someone other than a police officer has made the mistaken determination that resulted in the Fourth Amendment violation.” Herrera , 444 F.3d at 1249. 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 circumstan ces” that would convince us to “extend th[e] good-faith exception beyond its pedigree,” id. at 1253, we dec line to affirm on this basis.
D Finally, the government argues that we s hould affirm the dist rict court’s order because Bradley consented to a search of his entire reside nce. Nelson, in contrast, argues that the deputies reached the limit of Brad ley’s consent when they found and arrested Nelson. The district court expres sly declined to deci de this issue. There’s no dispute that Bradley authori zed the deputies to enter his residence in order to arrest Nelson. The question is whether Bradle y’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 “b lanket safety rule” that app lies “on any occasion in which [he] mak[es] an arre st” in a residence. Id. at 98. We note that if, as Nelson suggests, the United States Marshals Se rvice 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-i ntensive question of reasonable suspicion accommodate a policy of auto matic protective sweeps.” Hauk , 412 F.3d at 1186.13 beyond that purpose, authorizi ng the deputies to indiscrimina tely search the residence after the arrest. Bradley te stified about the scope of his consent as follows: Q. Okay. So you gave the U.S. ma rshals permission to go inside your house? A. Uh-huh. Q. And did you give the U.S. marsha ls 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 th e 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 “inc luded anything that [the deputies] needed to reasonably do to safely arrest” Nelson. Id. at 18. But Bradley never stated whether that license exte nded beyond the time of Nelson’s arrest. We won’t decide this issue in the fi rst 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 c ourt’s findings will be upheld unless they are clearly erroneous.” United States v. Pena , 920 F.2d 1509, 1514 (10th Cir. 1990). Although the govern ment raised this argume nt below—unlike its Prong One and good-faith arguments—the district c ourt declined to conduct the fact finding necessary for us to resolve this issue on appeal. We therefore remand for it to do so. Ramstad , 219 F.3d at 1265.14 * * * 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 ev idence already in the record, whether the deputies exceeded the scope of Brad ley’s consent when they continued searching his residen ce after they arrested Nelson.