You don't expect privacy in public in the sense that you might bump into other people that know who you are.
That doesn't automatically mean that you expect walking into a public area means a system will start investigating you and seeing if you match with crimes.
Assuming everyone in public is a suspect and continually investigating them, is a big change in how society works.
Well that's not exactly how it would work.
Everyone is tracked, but only certain people are watched. That added to the fact that any nation with a sufficiently complex legal system has no law abiding residents. You've always broken some law, somewhere.
So it would be more like:
>[Pick any person from] everyone in public [and the system has the capacity to list the reasons why that person] is a [criminal]
The "only certain people are watched" hinges on pinky swears, winks, and nods. IMO it's a distinction without a difference.