From what I hear of American police, what I've read in the news and statistics, and what I've seen on live footage, I'd say the only safe course of action is to keep the hands open and empty where the police can easily seem them, don't move without saying what you are about to do and why, and then move very slowly.
This post was edited by inky at June 29, 2019 9:02 PM MDT
Generally speaking - yes, if you are standing. But you should be aware of what "body language" that signals, and if it is appropriate for the situation.