The stop of Preinfalk’s car was lawful because in light of observations made by the officer, the anonymous tip provided reasonable suspicion to conclude the car was occupied by persons who had been involved in a fight at the Sidelines Bar:
¶11 It is not disputed that the tip in this case was anonymous. And I will assume, without deciding, the record does not contain any indicia of the informant’s veracity. However, regardless of this assumption, I conclude that the statements provided by the anonymous informant were nevertheless reliable in light of the evidence corroborating them. The caller stated that he or she was near the vicinity of Coal Street and that the perpetrators were getting into a Blazer and leaving Cole Street. Almost contemporaneously, Officer Wacker observed a green Chevy Blazer “leaving from directly in front of Sidelines” on Coal Street. The details of the statements provided by the anonymous caller were corroborated by Officer Wacker, bolstering the tip’s reliability “well enough to justify the stop.” See White, 496 U.S. at 327-332….
Preinfalk argued in part that the tip was unreliable because it provided “only readily observable information that any passerby could have provided”; besides rejecting the argument as undeveloped (¶11 n.2) the court cites State v. Williams, 2001 WI 21, ¶39, 241 Wis. 2d 631, 623 N.W.2d 106, for the proposition that corroboration of “innocent, although significant, details” of an anonymous tip bolsters its reliability.