State v. Kirby, 851 N.W.2d 796

Police responded to report of a large fight and related tip that the aggressor wore a Chicago Bulls cap and threatened to return with a gun.
Officers located apartment 1 where five men were present; one wore a Bulls cap matching the informant's description.
Officers questioned the men at the open apartment door; one officer stood a few steps inside the apartment while interviewing occupants.
During the encounter the investigator relayed an informant tip that a black backpack in the apartment contained a sawed-off shotgun and a handgun.
The officer (who had moved a few steps into the apartment) saw a black backpack on the love seat near the men, handcuffed the men for officer safety, opened the backpack, and found a loaded sawed-off shotgun.
Kirby was charged; he moved to suppress the evidence and later pleaded guilty but appealed the denial of suppression.

Issue	Plaintiff's Argument (Kirby)	Defendant's Argument (State)	Held
Whether officer crossing a few steps over the apartment threshold invalidated a warrantless search	Officer crossed threshold without warrant; Kirby had privacy/standing as frequent guest	Officer was lawfully present and exigent circumstances justified entry/search	Threshold crossing was immaterial; exigent circumstances justified search and seizure
Whether exigent circumstances justified warrantless entry/search for backpack	No exigency; needed warrant/consent	Informant tip of weapons near a group of men created risk to officer safety and potential violence	Exigent-circumstances doctrine allowed limited intrusion to locate/check backpack for weapons
Whether visual confirmation and seizure/opening of backpack was lawful	Opening backpack violated privacy and required warrant	Backpack matched tip and sat next to suspects; checking it was necessary to eliminate danger	Once backpack was observed near the men, exigency continued and justified seizure and opening
Whether Kirby retained an expectation of privacy in the backpack	Kirby claimed frequent presence in apartment and connection to backpack	Kirby disclaimed ownership and said backpack belonged to a third party; disavowal undermines privacy interest	Kirby’s disavowal (and placement of backpack in shared space) undermined any reasonable privacy expectation in the backpack

State v. Trecroci, 246 Wis. 2d 261 (discusses when a guest has a reasonable expectation of privacy in a host's premises)
State v. Garrett, 248 Wis. 2d 61 (defines exigent-circumstances standard justifying warrantless intrusion)
State v. Limon, 312 Wis. 2d 174 (permits limited warrantless search for weapons when officers are outnumbered and face safety risks)
Kentucky v. King, 131 S. Ct. 1849 (2011) (clarifies exigent-circumstances principles for warrantless entries)
State v. Whitrock, 161 Wis. 2d 960 (disavowal or lack of dominion over property undermines expectation of privacy)
State v. Tomlinson, 254 Wis. 2d 502 (consent to entry can be implied from conduct)