But an expert in use-of-force policies said Monday that the less-than- lethal weapons should be used as a last resort in the face of impending violence by demonstrators, such as arson, the use of Molotov cocktails or flipping cars over.

"Unless there's some intelligence that there's going to be a civil disturbance, why would you (use the weapons)? What threat is there?" said Geoffrey Alpert, a University of South Carolina criminologist.