One way that the police can stop you while driving in Arizona is if they have 'reasonable suspicion' that you've violated a motor vehicle law or were involved in some kind of criminal activity. That means that if you are speeding, make an improper turn, or break some other traffic law while driving in Arizona, the police may pull you over. It also means that if the police have reasonable suspicion that you were involved in some sort of other criminal activity, like a robbery or murder, they can pull you over and stop you as well. However, the police need to have a 'particularized and objective basis for suspecting the particular person stopped of criminal activity,' which means that they have to be able to articulate the objective facts that gave them suspicion that a motor vehicle law was broken, or that someone was involved in criminal activity. Once the police have reasonable suspicion that a driver broke the law, or was involved in criminal activity, the police can pull the car over and initiate a stop in order to investigate further.