First-hand observation by police of what appears to be obvious illegal activity is an unnecessary part of the reasonable-suspicion analysis for purposes of a simple investigatory stop. Such an observation, of course, would provide probable cause for an arrest. See People v. Timmsen, 2016 IL 118181 (Thomas, J. specially concurring).Instead, pursuant to Terry v. Ohio, 392 U.S. 7 (1968), police may initiate a brief investigatory stop of a person where police reasonably believe that the person has committed, or is a about to …