David New v. Dale Denver, 787 F.3d 895

Sergeant Dale Denver (Benton County) searched David New's car during a consensual traffic-stop search and found two dried leaves he concluded were marijuana; he arrested New and submitted the leaves to the crime lab.
Arkansas crime lab reported “no controlled substances detected”; the chemist noted variables that can cause false negatives and that the leaves had cystolithic hairs consistent with (but not unique to) marijuana.
New and his brother testified they believed the leaves were not marijuana and had tracked wet leaves into the car from their property; the leaves themselves are not in the summary-judgment record.
Denver testified he had 20 years’ experience and substantial drug-interdiction training, was “absolutely convinced” the leaves were marijuana, and acted by bagging the leaves, arresting New, and sending them for testing.
New sued under 42 U.S.C. § 1983 claiming arrest without probable cause (Fourth and Fourteenth Amendments). The district court denied Denver’s summary-judgment motion (on merits and qualified immunity), citing disputed credibility in light of the negative lab result and New’s contrary averments.
The Eighth Circuit majority reverses, holding (as a matter of law) Denver is entitled to qualified immunity; a dissent argues the court lacks jurisdiction under Johnson v. Jones because disputed facts remain for trial.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Is this interlocutory denial of qualified immunity immediately appealable (do disputed material facts preclude appellate review)?	New: District court correctly found genuine fact issues (Denver’s credibility) that preclude appellate resolution.	Denver: Disputed facts cited (lab report, New’s testimony) are not material to the legal question; appellate review is proper.	Majority: Appellate jurisdiction exists because the alleged contrary evidence is immaterial to the legal question of arguable probable cause; dissent: would dismiss for lack of jurisdiction under Johnson v. Jones.
Was Denver entitled to qualified immunity because he had arguable probable cause to arrest for marijuana possession?	New: No reasonable officer would conclude the leaves were marijuana given his testimony and the negative lab report.	Denver: His training, experience, contemporaneous observations, prior arrests of occupants, and routine post-find actions gave an objectively reasonable belief the leaves were marijuana.	Majority: Held Denver entitled to qualified immunity as a matter of law—an objectively reasonable officer could have believed the leaves were marijuana; reverse and dismiss with prejudice.

Harlow v. Fitzgerald, 457 U.S. 800 (qualified immunity standard)
Mitchell v. Forsyth, 472 U.S. 511 (appealability of immunity rulings)
Hunter v. Bryant, 502 U.S. 224 (courts should decide immunity early)
Devenpeck v. Alford, 543 U.S. 146 (probable-cause analysis depends on facts known to officer)
Whren v. United States, 517 U.S. 806 (pretext and officer’s subjective intent irrelevant to Fourth Amendment probable cause)
Texas v. Brown, 460 U.S. 730 (probable cause to seize apparent contraband)
Johnson v. Jones, 515 U.S. 304 (limits appellate review where genuine fact issues remain)
Pace v. City of Des Moines, 201 F.3d 1050 (8th Cir.) (when undisputed facts permit legal immunity determination)
Aaron v. Shelley, 624 F.3d 882 (8th Cir. 2010) (denial of immunity where investigation facts are materially disputed)
Brodnicki v. City of Omaha, 75 F.3d 1261 (4th Amendment probable-cause evaluation not exact science)