those are the words at the core of the immigration controversy, reasonable suspicion. a lot of people are asking how do you define that, and how far can police officers actually go to act on it? casey wian is in arizona to find out. reporter: john, kiran, we spent most of the day on patrol with one of the people who will be charged with enforcing arizona s tough new law, targetings illegal immigrants, much of what the law will require is already doing. sheriff s deputy mark miller approaches a pickup abandoned near a canal county road. this would be a typical vehicle. stolen truck, 4 by 4, heavy-duty. reporter: it s clearly been used by illegal immigrant smugglers, backpacks, flashlight, food. i ve seen upwards of 30 to 40 people in a vehicle this size. reporter: the bed is rigged so dozens can hold on for a wild ride. we take one as well, joining the pursuit of two vehicles spotted