City of Missoula v. Sharp, 358 P.3d 204

On Nov. 27, 2013 at ~10:00 p.m., Missoula Officer Lloyd observed Justin Sharp at the Front & Higgins intersection in downtown Missoula, an area with pedestrians and a 25 mph speed limit.
Sharp, in an older pickup, revved his engine when the light turned green and rapidly accelerated, pulling ahead of other cars and passing the parked patrol car.
Lloyd visually estimated Sharp was speeding and perceived the acceleration and speed as “aggressive” and unsafe given pedestrians and darkness; Lloyd then activated his lights and stopped Sharp a few blocks later.
During the traffic stop Lloyd observed slurred speech and the stop developed into a DUI investigation; Sharp was charged with DUI and related offenses.
Sharp moved to suppress evidence from the stop for lack of particularized suspicion; municipal court denied the motion, the district court affirmed, and Sharp appealed to the Montana Supreme Court.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether Officer Lloyd had sufficient objective data to form particularized suspicion for an investigatory stop	The State: Lloyd had objective, articulable facts (rapid acceleration, apparent speeding, time of night, pedestrians) that a trained officer could infer wrongdoing, justifying the stop.	Sharp: Officer lacked particularized suspicion because there was no radar confirmation and no certainty that a traffic offense occurred.	The Court held Lloyd had particularized suspicion based on the totality of circumstances (acceleration, perceived speeding, pedestrian area, nighttime) and affirmed the judgment.

State v. Larson, 358 Mont. 156, 243 P.3d 1130 (Mont. 2010) (articulable facts and totality of circumstances govern particularized suspicion analysis)
Brown v. State, 349 Mont. 408, 203 P.3d 842 (Mont. 2009) (discussing objective data required for stops)
State v. Gopher, 193 Mont. 189, 631 P.2d 293 (Mont. 1981) (adopting particularized suspicion standard citing United States v. Cortez)
State v. Morsette, 201 Mont. 233, 654 P.2d 503 (Mont. 1982) (particularized suspicion need not be certainty)
United States v. Cortez, 449 U.S. 411 (U.S. 1981) (totality of circumstances and common-sense inferences for reasonable suspicion)
State v. Hurlbert, 351 Mont. 321, 211 P.3d 874 (Mont. 2009) (officer may stop for observed speeding and expand inquiry if additional objective data arise)
State v. Brander, 321 Mont. 484, 92 P.3d 1173 (Mont. 2004) (multiple driving aberrations considered together can justify investigatory intrusion)