Reasonable Suspicion vs. Probable Cause
Reasonable suspicion must be based on more than a hunch—law enforcement officers must be able to put their suspicion into words. For example, law enforcement officers can't just stop someone and say, "She looked like she was up to something." They need to be more specific, such as, "She was standing under the overpass staring up at graffiti that wasn't there two hours earlier. She had the same graffiti pattern written on her backpack. I suspected that she had put up the graffiti."
Law enforcement officers need more proof to say they have probable cause than to say they have a reasonable suspicion. For example, "A store owner called to report someone matching her description tagging a wall across the street. As I drove up to the store, I saw her running away spattered with paint and carrying a spray can in her hand."