Thaxton called the police to report that she had been in a domestic with her boyfriend (Gordon) two days earlier. She was crying and whispering into the phone so that Gordon wouldn't hear her and know that she called. The two of them lived with another roommate who supposedly had warrants for his arrest, Gordon was on probation, and there were weapons all over the house. She complained of injuries, and said that they had argued about getting her help for her injuries. When asked if she could answer the door when the police got there she said "I guess, if he doesn't kill me first." She also told the dispatcher that if they found out that she had called the police "seriously, they are going to hurt me."
Officers arrived and made some form of non-consensual entry into the house (the decision doesn't really give much more detail than that). A couple officers waited upstairs with Gordon while another one met with Thaxton in the basement. She told them about how two days earlier Gordon had shoved her against a wall, breaking her glasses and causing her to fall and hurt her arm and neck, and that he had then swung a samurai sword at her. Gordon's story was that they had argued, but that's all. The roommate apparently wasn't around to give his statement.
Thaxton showed an officer to the bedroom where her broken glasses were. While following her to the bedroom he saw an unstrung crossbow (which he left alone), a loaded shotgun (which he temporarily seized for safety reasons). He also seized three samurai swords which were displayed in the basement, because Thaxton wasn't sure which of the three Gordon had swung at her.
Thaxton was evaluated by medics and transported to the hospital, Gordon was arrested. The officers locked up the residence and (illegally) retained possession of the shotgun. While on the way to the jail, the arresting officer learned that Gordon was a convicted felon. He was charged federally with being a felon in possession of a firearm.
Gordon moved to suppress all the evidence, but especially the shotgun. The trial court had none of it and he was convicted, and he renewed his arguments on appeal.
Gordon argued that the initial entry into the house was not justified by exigent circumstances because there was no immediate threat of injury. The court held that although the initial violence had been two days earlier, the facts known to the police through dispatch about Thaxton's current situation which support exigency. She was crying and afraid to leave the basement, and afraid she would be seriously harmed for calling the police.
Gordon argued that even if the initial entry was justified, once he and Thaxton were both contained any exigency was no more, and so further intrusion into the house (such as following Thaxton while she went to get her glasses) was unreasonable without Gordon's consent. The court disagreed with Gordon again. There were weapons all over the house, the whereabouts of the roommate were unknown, etc.
Gordon finally argued that even if the officer reasonably followed Thaxton to the bedroom, that he had no reason to seize the shotgun because he had no information that would tie it to a crime. And on this one he's only half wrong.
The initial seizure of the gun for safety reasons was valid. We can temporarily seize people or objects for our own safety or for the protection of others. It's a pretty simple precaution to take possession of a gun in a case like this. The trouble is that since there was no reason (yet) to believe that the gun was evidence of a crime, the shotgun should have been left in the house when the police left with Gordon.
Even so, the court declined to suppress the shotgun. Their reasoning was that the evidentiary nature of the gun became obvious within a few minutes (when the cop learned that Gordon was a felon), so he was only improperly deprived of his property for a few minutes during which he was in custody anyway. That kind of minimal violation does not, in the court's eyes, merit suppression. And although it wasn't argued by the government, the court noted that this would have been a good case of inevitable discovery. And besides all that, even if the shotgun were suppressed it would be a symbolic measure. It's not like they're going to actually give the gun back to a convicted felon, and even if the physical shotgun were not present as evidence in court, the officers (and Thaxton) would have been able to testify to it's presence in the home so Gordon would have been convicted anyway.