> Depending on the crime, most people would agree that face/gait recognition is warranted, for example in case of murder or rape

That's the problem with dragnet surveillance. People are okay with it for extreme cases. And then the scope creeps.

Free or secure. You can't have both. And you usually can't even have just the latter.

> And then the scope creeps.

Agreed and wanted to add. If it exists, can do the job, and the person in charge is aware of it, then it will inevitably be used. There's no such thing as "only for certain situations" unless there is a large inherent cost to using it outside of the proscribed scenario.

If you mandate the placement of fireman's axes by every door, at some point someone is going to use one of them to commit murder or vandalism or some other crime. There is effectively nothing that can be done to prevent that other than choosing not to mandate their placement.