In the following scenario, does the person have a reasonable expectation of privacy?
Assuming the police may bring a dog to "sniff" a vehicle stopped for a routine traffic violation, can the police detain the vehicle and its passengers beyond the time needed to handle the traffic stop?
I think that more detail will be needed in being able to fully address the issue of privacy. The first thing that jumps out in my mind is the establishment of probable cause to initiate the search. From the description offered, it seems that there is little in way of probable cause to bring out the police dog on a routine traffic violation. I think that more of a discussion of probable cause is needed in this explanation, in terms of why the police would jump to the use of a police dog in such a situation on something as routine as a traffic violation. If there is sufficient probable cause, then I think that the use of a dog could be warranted, but, as I said, more detail is needed in this setting. On the issue of detainment, I think that this is a bit more open to interpretation. Ensuring the due process of any individual who is detained by the police is a fairly time consuming process. This might involve conducting an examination of the driver’s license of the individual driving and the license and registration of the vehicle. This takes time and while I am sure all attempts are made to make this a “speedy” process, I think that this can be seen as detaining individuals. In the interests of further due process, or the extensive right of each individual’s ability to be heard, I think that time consumption can be seen as a part of this. To what extent this is “stretchable” by the individuals could be seen as another part of the equation of reasonable expectation of privacy.
Given the facts you have provided, and assuming this was a routine traffic stop, and there is no independant probable cause to search the vehicle, no, you may not detain the vehicle and occupants beyond the time required for the traffic stop itself.
However,should there be independant probable cause to search the vehicle- the smell of marijuana coming from the vehicle for example- then you make briefly detain the vehicle and occupants while you search (you are now conducting a "Terry stop"), and you may bring the dog to scene. The question of how long you make detain them while searching/bringing the dog has been the subject of a number of appellent cases over the years, and there is no hard and fast tule.