Mr. Nelson challenged the search as a violation of Maryland v. Buie, a 1990 Supreme Court opinion which held that,
[T]he Fourth Amendment would permit the protective sweep undertaken here if the searching officer possessed a reasonable belief based on `specific and articulable facts which, taken together with the rational inferences from those facts, reasonably warranted the officer in believing that the area swept harbored an individual posing a danger to the officer or others(internal marks omitted).Following Buie, here Judge Mortiz wrote, "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."
This case is quite fact-dependent, but notable for a few reasons. First, the Court held that the government waived a several arguments because they had not been raised below. Second, the Court rejected the government's curious good faith argument for the obvious reason 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.”
And third, the Court also took time to address the KCK U.S. Marshal's policy and practice of a "blanket safety rule," conducting a sweep every time that they enter a residence to make an arrest:
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.” Hauk, 412 F.3d at 1186.Congrats to Dan Hansmeier.