The officer has to be aware of parole or probation search waiver before the search happens, if that’s the justification. United States v. Job, 2017 U.S. App. LEXIS 4428 (9th Cir. March 14, 2017):
First, it is undisputed that the officers were unaware of Job’s Fourth Amendment search waiver when they stopped him and patted him down. The district court did not determine whether the officers were aware of the search waiver before conducting the search of his person and the search of his car. It based its decision solely on the fact that Job was subject to a Fourth Amendment search waiver at the time of the searches. Police officers must know about a probationer’s Fourth Amendment search waiver before they conduct a search in order for the waiver to serve as a justification for the search. In United States v. Caseres, we concluded that a “search is not justified by the state’s interest in supervising” parolees when the officers were unaware of the waiver before the search. 533 F.3d 1064, 1076 (9th Cir. 2008); see also Moreno v. Baca, 431 F.3d 633, 641 (9th Cir. 2005) (holding that “police officers cannot retroactively justify a suspicionless search and arrest on the basis of an after-the-fact-discovery of … a parole [search waiver] condition”). This reasoning also logically applies to probationers, who have a higher expectation of privacy than parolees. Lara, 815 F.3d at 610 (citing Samson v. California, 547 U.S. 843, 850, 126 S. Ct. 2193, 165 L. Ed. 2d 250 (2006)). 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.