Can a Fourth Amendment search waiver be used to justify a search of a probationer's car?

search waiver gave the officers a valid justification for the search. The police report suggests that the officers may have learned about the search waiver during a records check after the officers patted Job down, but before they searched his car. The district court made no finding on this fact, however, and Job argues that the record is at least unclear as to when the officers learned of Job's Fourth Amendment search waiver. We agree. As we noted above, a Fourth Amendment search waiver cannot provide a justification for a search of a probationer where the officers were unaware of the waiver before they undertook the search. From this record, we cannot conclude that the government has proved by a preponderance of the evidence that the officers knew about the search waiver before searching Job's car. See United States v. Vasey , 834 F.2d 782, 785 (9th Cir. 1987).⁴