Does a finding that Rivers consented to a search warrant issued by a federal judge that the search violated the Fourth Amendment?

We give substantial deference to the district judge's apparent acceptance of the agents' testimony that Rivers orally consented to the search, was given a consent form to read, and again consented. See United States v. Ramos, 923 F.2d 1346, 1356 (9th Cir.1991). On this evidence, the district court's finding that Rivers consented was not clearly erroneous.

Furthermore, we need not reverse because the district court failed to determine whether Rivers voluntarily consented. A violation of the Fourth Amendment does not mandate reversal of a conviction if the error was harmless beyond a reasonable doubt. See Delaware v. Van Arsdall, 475 U.S. 673, 681 (1986); United States v. O'Connor, 737 F.2d 814, 821 n. 6 (9th Cir.1984).