Can I walk away from a police officer?
If a officer approaches you and engages you, simply ask “Am I free to go?”
If he says yes, then go.
If he says you are not free to go then, consider yourself stopped, detained and soon to be arrested. Exercise your right to remain silent.
If he has a reason to detain you he must issue a command for you to stop. If he does then you must stop, but you do not have to speak.