In the years that followed Mapp, the Court continued to engage in defining what constituted an illegal search. In Spinelli v. United States (1969) it sought to determine what constituted probable cause to issue a search warrant. It set forth a two-prong test that had to be met before information received from a police informant could be used, which placed substantial impediments on the use of such information. That same year in Terry v. Ohio the Court also established a test for determining when a policeman could stop a person engaged in suspicious activity and search them for the limited purpose of finding any weapons. The Court said such a search was permissible if the facts available were sufficient "to warrant a man of reasonable caution in the belief that the action taken was appropriate." This "stop and frisk" rule was very subjective...