State v. W. Harning, 507 P.3d 145

Trooper DiGiovanna stopped William Harning for speeding (74 in a 65) near Billings on March 1, 2018; he observed sealed boxes in the truck bed and the driver rolled his window down only 3–4 inches.
The trooper smelled marijuana "wafting" from the vehicle; Harning admitted smoking marijuana earlier in Big Timber (about 80 miles before the stop) and denied having a medical marijuana card.
The trooper conducted a DUI investigation (field sobriety tests), patted Harning down (no drugs found), concluded Harning was not impaired, but told Harning he was not free to leave pending a drug investigation.
Trooper called for a canine; after ~17 minutes a K-9 arrived, alerted to the vehicle, a search warrant issued, and officers found a glass pipe and grinder; Harning was charged with possession and paraphernalia.
Justice Court denied Harning’s motion to suppress; District Court affirmed; the Montana Supreme Court reversed, holding the trooper lacked particularized suspicion to extend the stop into a vehicle drug investigation.

Issue	State's Argument	Harning's Argument	Held
Whether particularized suspicion existed to extend a traffic/DUI stop into a drug investigation (canine sniff/search of vehicle)	Trooper had specific, articulable facts (marijuana odor, admission of recent smoking, evasive answers, speeding) that justified expanding the stop and deploying a canine	Trooper only had generalized suspicion (nervous/evasive behavior and a stale admission of smoking miles earlier); once DUI cleared, stop should have ended and further detention/search required particularized suspicion	Reversed: no particularized suspicion to extend the stop into a drug investigation; canine search was unlawful and evidence must be suppressed

Rodriguez v. United States, 575 U.S. 348 (2015) (traffic-stop "mission" limits permissible detention duration and unrelated inquiries may not prolong it)
State v. Wilson, 430 P.3d 77 (Mont. 2018) (post-stop nervous behavior alone, without objectively incriminating facts, does not create particularized suspicion)
State v. Estes, 403 P.3d 1249 (Mont. 2017) (scope of an investigatory stop may expand when new particularized facts arise)
State v. Tackitt, 67 P.3d 295 (Mont. 2003) (a canine sniff of a vehicle is a search under Montana Constitution)
State v. Pierce, 116 P.3d 917 (Mont. 2005) (odor plus admission that someone smoked in the vehicle supported probable cause; distinguishable from stale or non-vehicle admissions)
Taylor v. United States, 286 U.S. 1 (1932) (odor alone does not automatically permit a warrantless search)
Weeks v. United States, 232 U.S. 383 (1914) (exclusionary principle: evidence from unconstitutional searches must be suppressed)