> Person running down the sidewalk pursued by someone shouting "stop, thief!" gets tackled by a cop and cuffed. Turns out to be mistaken identity or they'd done self-checkout.

Not sure that'd be a rights violation. The cop would be able to say they had reasonable suspicion that a crime was being committed justifying the detention. Excessive force is a possibility depending on the details, such as the extent of the injuries that resulted from being forced to the ground or if the cop ordered the runner to stop before tackling them.