rant. Wollman relayed this information to other law enforcement officers in the area, including Trooper John Stahl of the South Dakota Highway Patrol. Shortly thereafter, Stahl saw the vehicle Garreau was driving, determined that it was traveling in excess of the posted speed limit, and signaled him to stop.
Stahl issued Garreau a warning citation for speeding and ran a computer check on Garreau’s driver’s license. The check confirmed that Garreau’s license had been suspended. Stahl also confirmed by way of radio that Garreau was subject to arrest on an outstanding state warrant. Stahl arrested Garreau, searched his person, and placed him in the back of the patrol car.
Stahl asked Garreau whether there was anyone available to pick up the vehicle that Garreau had been driving. Garreau answered in the negative. According to Stahl, he then called for a tow truck to take the vehicle into protective custody, and performed an inventory search of the vehicle. He found the firearm in a plastic bag under a spare tire, which was in a compartment under the carpet on the floor of vehicle’s trunk. Stahl inquired about the firearm’s serial number over his radio, and confirmed that the gun was stolen.
A federal grand jury charged Garreau with possession of a stolen firearm, in violation of 18 U.S.C. § 922(j), and possession of a firearm by an unlawful user of a controlled substance, in violation of 18 U.S.C. § 922(g)(3). Garreau moved to suppress the firearm, on the ground that Stahl searched the vehicle in violation of the Fourth Amendment. He also sought, based on Miranda v. Arizona, 384 U.S. 436, 86 S.Ct. 1602, 16 L.Ed.2d 694 (1966), to suppress certain inculpatory statements he made at the scene of the stop, and to exclude inculpatory statements he made and a urine sample he gave at a jail following the arrest as fruits of an unlawful search. See Segura v. United States, 468 U.S. 796, 804, 104 S.Ct. 3380, 82 L.Ed.2d 599 (1984).
A magistrate judge recommended denial of Garreau’s motion to suppress. The magistrate concluded that Stahl’s search of the vehicle was a valid inventory search that complied with the Fourth Amendment. The magistrate also determined that Garreau’s statements at the scene of the stop were obtained in violation of Miranda. But the government declared its intention to use those statements only to impeach Garreau’s trial testimony, and the magistrate concluded that the statements were admissible for that limited purpose. Finally, the magistrate recommended that Garreau’s statements at the jail and the urine sample should not be suppressed, because the search of the vehicle was not unlawful, and because the statements and the sample were not tainted by the Miranda violation.
The district court agreed with the magistrate’s recommendation, except with respect to the search. The court concluded that the search was an unlawful search incident to arrest, not a valid inventory search, but the court did not suppress the firearm. Rather, the court ruled that the firearm was admissible under the inevitable discovery exception to the exclusionary rule because it would have been discovered during a later, lawful inventory search. Garreau thereafter entered a conditional guilty plea to possession of a stolen firearm and appealed the denial of the motion to suppress.
II.
Garreau argues that the district court erred by relying on the inevitable discovery doctrine. He contends that the government relied in the district court exclusively on its position that Stahl conducted a valid inventory search and waived all other arguments in support of the fire