Rules that govern encounters are determined by the purpose of police conduct, whether an officer has “seized” an individual, and the strength of available evidence. The Fifth Amendment requires warnings at the time of an arrest. Specific rules for conduct during an encounter are outlined. These involve a wide variety of situations, including casual encounters, roadblocks, canine assists, tips, pretext stops, Terry stops, frisks, plain touch seizures, execution of warrants, and vehicle stops and pursuits.