State v. M. Zeimer, 510 P.3d 100

At ~9:00 a.m., deputies responded to a 911 welfare-check of a truck parked across spaces with the driver slumped over the wheel; the driver (Zeimer) awakened and drove to the front and parked.
Deputy engaged Zeimer, who produced ID and gave inconsistent answers about why he was at the Town Pump; deputies made calls (including to a purported sister) and repeatedly questioned him about his story.
Deputies delayed conducting DUI-confirmatory field sobriety tests for over 20 minutes, instead conducting extended non-DUI questioning and a contested pat‑down that reached into pockets.
Only after ~20 minutes was Zeimer taken aside for HGN, walk‑and‑turn, and one‑leg‑stand; later he was seated in a locked patrol car, read Miranda, and asked to consent to a vehicle search.
Zeimer signed a written consent; deputies searched the truck, discovered methamphetamine and paraphernalia, arrested him, and he was charged; he later pleaded guilty while reserving the suppression issue.
The district court denied suppression; the Montana Supreme Court held the deputies unlawfully prolonged the investigative DUI stop, applied the exclusionary rule, and reversed Zeimer’s convictions.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Validity of initial encounter (welfare check vs. seizure)	Initial facts justified at least a Terry investigative stop for DUI.	CCD (welfare) justification ended when Zeimer drove to the front; any extension required new suspicion.	Initial stop was lawful as a DUI‑focused investigatory stop (Terry standard satisfied).
Whether deputies lawfully prolonged the stop before DUI testing	Any additional questioning was related to the stop and did not unreasonably prolong it.	Deputies delayed DUI confirmatory testing >20 minutes while pursuing unrelated lines (drug/narrative interrogation), exceeding scope/duration.	Deputies unlawfully prolonged the stop before sobriety testing; delay was unreasonable.
Lawfulness/scope of pat‑down/frisk	Frisk was for officer safety and permitted; items found justified further inquiry.	Frisk lacked particularized suspicion that Zeimer was armed; intrusive pocket searches exceeded Terry scope and were pretextual.	Pat‑down/search exceeded Terry limits and showed deputies were not diligently pursuing DUI inquiry.
Admissibility of evidence from vehicle search	Consent to search was voluntary; vehicle search was independent and valid.	Consent and search flowed from the unlawfully prolonged stop and were tainted (fruit of the poisonous tree).	Evidence was product of the unlawful extension; exclusionary rule required suppression; convictions reversed.

Terry v. Ohio, 392 U.S. 1 (1968) (authorizes brief investigative stop on particularized suspicion)
United States v. Cortez, 449 U.S. 411 (1981) (totality-of-the-circumstances test for reasonable suspicion)
Florida v. Royer, 460 U.S. 491 (1983) (limits on detention scope/duration and consent obtained after illegal extension)
Rodriguez v. United States, 575 U.S. 348 (2015) (unrelated checks cannot measurably extend a traffic stop absent new suspicion)
Minnesota v. Dickerson, 508 U.S. 366 (1993) (plain‑feel exception; limits on tactile manipulation during frisk)
Hulse v. Montana Dept. of Justice Motor Vehicle Div., 961 P.2d 75 (Mont. 1998) (field sobriety tests and DUI investigative-suspicion principles)
State v. Laster, 497 P.3d 224 (Mont. 2021) (new or broader suspicion must arise during lawful stop to expand scope/duration)
State v. Martinez, 67 P.3d 207 (Mont. 2003) (stop cannot last longer than necessary to effectuate its purpose)
Mendenhall v. United States, 446 U.S. 544 (1980) (definition of seizure; reasonable‑person test)
Katz v. United States, 389 U.S. 347 (1967) (Fourth Amendment protects people, not just places)