... possible criminal behavior means "I have a reasonable, articulable suspicion that ya doin' wrong"of investigation of possible criminal behavior even though there is no probable cause for arrest.
Again, the step right before having probable cause to arrest is to reasonably suspect that crime is afoot.Police officers may make a limited stop on less than probable cause. People v. Montoya, 185 Colo. 299, 524 P.2d 76 (1974).
Basically, what the courts seem to be saying, is that IF there is a reasonable, articulable suspicion of a crime, an officer is authorized by law to conduct an investigation to determine if that suspicion is correct. If such suspicions are confirmed then there is probable cause that a crime has occurred and an arrest is warranted.