Reasonable suspicion

Reasonable suspicion is the lowest legal standard of proof in United States law, below that which is "reasonable to believe" and that which gives probable cause to issues search and arrest warrants. Reasonable suspicion is greater than an "inchoate and unparticularized suspicion or 'hunch' "; it must be based on "specific and articulable facts", "taken together with rational inferences from those facts".

Police may briefly detain a person if they have reasonable suspicion that the person has been, is, or is about to be engaged in criminal activity; such a detention is known as a Terry stop. If police additionally have reasonable suspicion that a person so detained may be armed, they may "frisk" the person for weapons, but not for contraband like drugs.

Reasonable suspicion is evaluated using the "reasonable person" or "reasonable officer" standard, in which said person in the same circumstances could reasonably believe a person has been, is, or is about to be engaged in criminal activity; it depends upon the totality of circumstances, and can result from a combination of particular facts, even if each is individually innocuous.