Is the search of a vehicle, with the driver’s consent valid? 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?

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?