Orin Kerr writes:
Here’s an interesting Fourth Amendment question decided by the 8th Circuit last year in United States v. Cowan, 674 F.3d 947 (8th Cir. 2012): If the police have a suspect’s car keys, and the key fob has an electronic button that sets off the car’s alarm when pressed, can the police press the button to set off the alarm and therefore identify which car belongs to the suspect? In Cowan, the officers had seized the suspect’s keys, and they suspected that the suspect’s car was nearby and might contain drugs. To identify which car belonged to the suspect, they walked around the streets near his home pressing the “alarm” button until a specific car’s alarm siren was triggered. They then brought in a drug-sniffing dog to sniff that car, the dog alerted, and a search of the car revealed crack cocaine inside.
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