In general, talking to the police is not in your best interest. "Can I speak to you, please?" The answer is "No, officer." You don't need a reason. If you are TOLD to stop, ask if you are being detained. Further questions should involve their RAS for holding you. Keep repeating, "Officer, am I free to leave?" But cops are real people and may just want to talk to you. I've had a few short conversations with the police while high. One time I bought three Grape Dutchmasters and a pack of Zig Zags at a convenience store. It wasn't until I turned around that I noticed the Sheriff's Deputy behind me. He nodded and then said "Don't you hate how those cigars are always dried out?" If he wasn't on duty I might have told him "Yes sir, it makes it difficult to get the leaf off in one piece and split the fucker without a knife. Plus, they taste a lot better fresh."