City of Milwaukee v. Nelson

Milwaukee's ordinance criminalized loitering "in a place, at a time, or in a manner not usual for law-abiding individuals" under circumstances warranting alarm, factoring in flight or concealment, and requiring officers to give suspects a chance to explain before arrest. Police watched Nelson (defendant) shake hands repeatedly with pedestrians and passengers outside a tavern without seeing money or objects exchanged, and he retreated inside each time officers approached; when questioned, he said he was doing "nothing" and was arrested for loitering after a pat-down revealed no weapon. A gun later found in the police van, which Nelson admitted was his and had hidden, led to a concealed-weapon charge, which he challenged by arguing the loitering ordinance underlying his arrest was unconstitutional.