Commonwealth v. Yong, 120 A.3d 299

Police narcotics surveillance at 3200 block of N. Fairhill St.; Officer McCook used a confidential informant (CI) for controlled buys on Sept. 21–23, 2011.
On Sept. 21 McCook observed Yong accept $120 from the CI and hand the money to co-defendant Vega, who returned with marijuana packets and sold them to the CI.
On Sept. 23 officers executed a search warrant at 3202 Fairhill. Officer Gibson (who did not testify at the suppression hearing) immediately arrested Yong inside the residence and found a concealed loaded .38 revolver.
At the suppression hearing McCook testified about the Sept. 21 buy but did not testify that he told Officer Gibson or ordered Yong’s arrest; no testimony showed communication between McCook and Gibson about the prior buy.
Trial court denied Yong’s motion to suppress by imputing McCook’s knowledge to Gibson under the collective-knowledge doctrine; jury later convicted Yong of firearm and conspiracy offenses.
Superior Court reversed the denial of the suppression motion, holding the Commonwealth failed to show Gibson had probable cause or that McCook directed Gibson to arrest (declining to adopt a broad “horizontal” collective-knowledge rule).

Issue	Yong’s Argument	Commonwealth’s Argument	Held
Whether the warrantless arrest and search of Yong were supported by probable cause or reasonable suspicion	Gibson lacked probable cause or reasonable suspicion; Guan argued arrest was unlawful because no evidence Gibson knew of Sept. 21 transaction	McCook’s knowledge could be imputed to Gibson under the collective-knowledge doctrine (aggregate officers’ knowledge)	Reversed suppression denial: no evidence Gibson received direction or information; collective-knowledge applies only when an officer with probable cause directs another (vertical), not to post-hoc aggregation (horizontal)
Whether evidence was sufficient for conspiracy conviction	Trial evidence insufficient/ inconsistent (argued report vs. testimony)	Evidence showed agreement and concerted conduct—Yong accepted money while Vega distributed drugs—sufficient circumstantial evidence for conspiracy	Sufficient: conviction on conspiracy upheld (but retrial on other counts permitted after suppression ruling)

Williams v. United States, 308 F.2d 326 (D.C. Cir. 1962) (articulated collective-knowledge / fellow-officer rule where arresting officer acts on another officer’s information or direction)
Whiteley v. Warden, 401 U.S. 560 (U.S. 1971) (limited collective-knowledge: arresting officer may rely on bulletin but cannot be insulated when instigating officer lacked probable cause)
Hensley v. Municipal Court, 469 U.S. 221 (U.S. 1985) (collective-knowledge rationale: officers may act on information transmitted by colleagues to enable prompt action)
Brinegar v. United States, 338 U.S. 160 (U.S. 1949) (probable cause is a practical, nontechnical standard based on probabilities and reasonable conclusions)
Commonwealth v. Kenney, 297 A.2d 794 (Pa. 1972) (Pennsylvania adoption of Whiteley’s rationale: warrantless arrest upheld where arresting officer acted on superior’s direction who had probable cause)
Commonwealth v. Rodriguez, 585 A.2d 988 (Pa. 1991) (defines probable cause standard for warrantless arrests in Pennsylvania)