State v. Matthew Elliot Cohagan, 162 Idaho 717

Officers Curtis and Otto saw Cohagan on a street corner and believed he resembled a person with outstanding warrants; Cohagan entered a grocery store before officers returned.
Officer Otto first checked Cohagan’s ID and determined he was not the person suspected; both officers then left the store to retrieve unrelated surveillance video.
Officer Curtis later re-approached Cohagan in the store, requested his ID, retained it, and ran a warrant check; the State conceded that retaining the ID effected an unlawful seizure.
Dispatch initially suggested Cohagan might have a warrant; Officer Curtis intercepted Cohagan, prevented him from continuing to shop, and escorted him to the front of the store where officers confirmed outstanding warrants and arrested him.
A search incident to arrest uncovered methamphetamine paraphernalia; Cohagan moved to suppress, the district court denied the motion, Cohagan pleaded guilty conditionally, the Court of Appeals reversed, and the Idaho Supreme Court granted review.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Legality of the seizure when officer retained Cohagan’s ID	State conceded retaining the ID was an unjustified seizure	Cohagan argued the retention was an unlawful detention invoking the exclusionary rule	Court treated the retention as an illegal seizure (State had conceded)
Whether discovery of a valid warrant attenuated the taint so evidence need not be suppressed	State argued the valid warrant was an intervening circumstance breaking the causal chain (attenuation)	Cohagan argued the warrant discovery did not sufficiently attenuate because seizure was close in time and the officer’s conduct was flagrant	Court held attenuation failed: short temporal proximity and officer’s purposeful/suspicionless conduct outweighed the intervening-warrant factor, so evidence suppressed

Mapp v. Ohio, 367 U.S. 643 (exclusionary rule applies to the states)
Wong Sun v. United States, 371 U.S. 471 (fruit of the poisonous tree/derivative evidence rule)
Segura v. United States, 468 U.S. 796 (independent source doctrine discussion)
Brown v. Illinois, 422 U.S. 590 (attenuation factors and analysis)
United States v. Leon, 468 U.S. 897 (good-faith exception and police training rationale)
Utah v. Strieff, 136 S. Ct. 2056 (attenuation doctrine; discovery of valid warrant can strongly favor attenuation)
Arizona v. Gant, 556 U.S. 332 (search incident to arrest principles)
State v. Page, 140 Idaho 841 (Idaho precedent on retention of ID from pedestrians and attenuation analysis)