Is a witness report reasonable suspicion for a stop?

Yes. This follows under Terry vs. Ohio (Terry Stop).

Information conveyed by third parties.

-Known sources are reliable, but information must provide Reasonable Articulable Suspicion of criminal activity.

-Unknown sources must corroborate to establish reliability and Reasonable Articulable Suspicion of criminal activity. Examples: Alabama vs. White (1990) Specific detail that collaborates future events

-Fellow officer sources are reliable, but information must provide Reasonable Articulable Suspicion of activity. It justifies both Terry Stop and arrest.