[kgoerz]

This is what was taught at the academy in 2007. A Cop can make contact with a person in a public place. It's actually a security technique.
If someone is up to no good it's pretty easy to tell just by engaging them in conversation. Seems like just conversation but the cop is actually looking for certain reactions. Like if your in an airport but hesitate when asked "where are you heading to today"
You can continue to walk and tell the cop you don't have the time. It's when the cop try's to make you stop. Then he is detaining you. He is keeping you from getting to your destination. Thats when they technically need a reason to keep you from continuing on.