Durham, North Carolina, police set up a roadblock on Elliott Road, a major road that runs through town and close by the Duke University campus.Their intention is to stop every vehicle that passes through this roadblock and ask the driver to produce his or her driver's license and vehicle registration.State law requires drivers to carry these documents with them any time they are operating a motor vehicle.The officers also hope to determine if any of the drivers may be transporting drugs, as there have been a number of arrests for drug use and sale in the area, particularly on the Duke University campus.

After stopping and verifying the driver's license and registration, the police ask the drivers if they can search their vehicles.Those drivers who give consent have their vehicles searched; those who do not give consent are detained roadside while a narcotics detection dog sniffs the detained vehicle; the sniff is usually done within five minutes.

1. Is the roadblock to check license and registration valid?What Supreme Court case can you find that deals with this and what was their decision?
2. Is the search of a vehicle, with the driver's consent valid? Explain why or why not.
3. Is the use of the dog to sniff the detained vehicle valid? Why or why not?What Supreme Court case can you find that deals with this (in particular with roadblocks) and what was their decision?
4. If drivers are detained for usually only five minutes, what does the Supreme Court say about this? What if the detention is longer - say 20 minutes?What does the Supreme Court say about that?