You as an individual will have no clue if police have reasonable suspicion or probable cause to detain and identify you. Police do not have to tell you why, they do not have to prove they are in the right. If you do not comply then you are criminally charged with non compliance, refusing to identify, obstruction of investigation, etc. And now you are arrested.

Reality is police have far too much power, and the few cases they lose mean nothing to them. That's covered by insurance, paid by tax payers, and those officers never face criminal charges for their criminal acts, because DA's value their jobs.