â€œYou talk to people to observe their behavior,â€ Candelaria said. â€œIf you were a drug courier, nervousness is very difficult to suppress. I teach officers to pay attention to what they are doing and watch them in the environment they are in. After awhile they learn to pick out people.â€
The officers have a right to board the bus even without probable cause as long as the bus line gives them permission, University of Oklahoma law professor Randall Coyne said.
â€œProbable cause is a precise legal standard,â€ he said. â€œWhat you find far more often is they are excused from a lack of a warrant because of various circumstances that arise or because they have been given permission to be there.â€
Candelaria said he expects buses and trains will continue to be attractive to smugglers in the future. Though personal cars and trucks are also in high use, buses are cheap and easy in many cases.
â€œThey look for the best way to get from point A to point B and sometimes the easiest method of conveyance is a bus,â€ he said. â€œThe good thing is the companies are very cooperative and have an interest in helping police make arrests.â€