The following excerpt is from United States v. Johnson, 913 F.3d 793 (9th Cir. 2019):
showing of probable cause is valid if the officer arrests the suspect afterward, but becomes illegal if the officer subsequently decides not to make an arrest (say, because the search turns up nothing). See Menotti v. City of Seattle , 409 F.3d 1113, 1153 (9th Cir. 2005). That approach is at odds with the background principle that the reasonableness of a search turns on "whether the officers action was justified at its inception, and whether it was reasonably related in scope to the circumstances which justified the interference in the first place." Terry v. Ohio , 392 U.S. 1, 1920, 88 S.Ct. 1868, 20 L.Ed.2d 889 (1968). Beyond that, we should be skeptical of any rule that provides officers with an incentive to make an arrest they would not otherwise have made, solely to insulate themselves from civil liability for violating an individuals Fourth Amendment rights.
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