As mentioned by Scott Buhrmaster in a previous post.
Here is a TEST that I use on occasion when I have determined that the guy is DUI and is going to be arrested.
I instruct him to place his arms out in from of him, as if he is reaching for something. I then tell him to touch his thumbs together. Then I tell him to move his arms outward, and around to his back keep the arms extended. Then I tell him to touch his thumbs together behind his back, and to turn around so that I can see that his thumbs are together. He is concentrating on keeping his thumbs together and turning around that by the time I grab his thumb in a tactical grab and begin to cuff him, he is wrapped up and ready for transport before he knows what happened. It¿s even better when the guy realized you tricked him, and he starts laughing, or if he is mad, it¿s too late for him to do anything.