It depends on tone. If the cop starts aggressive, that's when you start using flat refusals. My suggestions were for the more common case: where the cop is casu

It depends on tone. If the cop starts aggressive, that's when you start using flat refusals. My suggestions were for the more common case: where the cop is casual, friendly and trying to lull you into a false sense of security. There can be value in playing a little dumb.