United States v. Dalton, 918 F.3d 1117 (10th Cir. March 21, 2019)

In what appears to be a case of first impression, the Tenth Circuit held evidence obtained during a search pursuant to a search warrant was seized in violation of the Fourth Amendment because the warrant had become stale, not due to the passage of time but because of the officer’s subsequent discovery of additional information.  The court held that “probable cause becomes stale when new information received by the police nullifies information critical to the earlier probable cause determination before the warrant is executed.”  Here, the probable cause had become stale because the officers had become aware the defendant was not the driver of the car in which officers had observed a firearm, a fact that had served as the basis for the probable cause he was illegally possessing a firearm in the house.