The idea was that a crime could be detected before it happened by computerized scanning of the crowd for suspicious behavior, such as walking too fast. They claimed to have observed from their previous spying on the public that fast walking preceded a significant amount of assaults.
So you'd need to walk slowly with your hands by your sides and don't make any suspicious or sudden movements, if you don't want to be stopped for questioning.
No, I'm not making this up. I saw the article here on FR, but unfortunately I didn't save it.
I can't keep track of all the posts either.
I have a book on body language. It does tell what's going on inside a person pretty well. It's based on conditioned responce.
Some people just walk fast, though. It shows they're busy and/or their mind is occupied.
Crossing arms shows defensiveness.
People may have something on their mind other than crime, but the body movements would be similar. It's just nerviousness. It happens in life all the time.
Pretty scary for the innocent citizen, aye?.