There's a difference between being observed and being recorded. Given:
- Constable Alice is earnest, honest, and clever, but a little bit lazy.
- Captain Bob is not so lazy, believes in delegating where ever possible, and will listen to a good argument for something - but only if it's short.
- Carol met some nice ladies at the country club last month, two of whom have sons of suitable age for her daughter to date. They're all kinds of fun to hang with!
- Detective Dave sees Carol (previously unknown) hanging out a lot recently with some probable high-end fences he's been investigating, and asks Captain Bob to get someone to put Carol under surveillance.
What is the minimum amount of work and paperwork required by Alice before Dave can say (without perjury) on the stand, "We put Carol under surveillance", and Bob can say, "I can't fire her, she did her job exactly as I put to her"?
You'll note that I didn't specify the kind or depth of surveillance. This is deliberate and not an attempt to be vague. I believe you'll figure out for yourself that the bar for Constable Alice can be very very low, and folk more imaginative than you or I could make it lower. Alice, having an actual incentive, might make it much lower than that. This might be the most important legal question society can discuss at the moment; being in a public place and able to be seen by the police doesn't mean you should be recorded by the police. Oddly, applying the same question and reasoning to "Automatic Number Plate Recognition" devices makes them look exceptionally intrusive. Oh, wait...