My 9 year old has a nasty attitude. How do I get him to listen and stop mouthing off? I have tried…

My 9 year old has a nasty attitude. How do I get him to listen and stop mouthing off? I have tried everything and nothing works. I told him if he keeps it up he will be in a lot of trouble. I even want to have the local police department to talk to him. Not sure what to do anymore.